Worth changing 40 gal. to 30gal. hot water tank?

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Valuethinker
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Valuethinker » Fri Nov 10, 2017 10:33 am

neilpilot wrote:
Fri Nov 10, 2017 8:20 am
Valuethinker wrote:
Fri Nov 10, 2017 4:14 am

I think the consensus is this is not a good idea for reasons of convenience and resale (would put off some buyers, potentially).

New tanks are very energy efficient - you can get one with excellent insulation (one form of loss is via the ground, so insulated feet help). Energy consumption thus similar. Cost of a 40 gallon and a 30 gallon should be similar.

Your main problem may be a change in dimensions *that* could force you to downsize.

The real alternative is to go tankless. A lot of considerations there, for a couple that should work but it will have inconvenience. I am a fan of sticking to what works (i.e. retain current approach, get a new highly insulated tank)-- avoids having to replace the burner.
I'm mostly in agreement except at the end when you suggest you avoid "having to replace the burner ". What gas water heater has an option of a tank replacement without an integral burner?
That's a Valuethinker American English translation error ;-).

Here (UK) we have a "boiler"-- the hot water is heated indirectly by the same furnace (boiler) that heats the water in the radiators. So what I mean was "replace the thing that heats the water". Agree it's a totally different bit of kit and if I'd thought about it, I would not have written "burner". I was trying to get an idea across and got lazy and did not think it through :( :?

My tank is called a "Megaflo cylinder" and it cost a bomb-- but the heat loss parameters are really impressive. 110 litre is close to US 40 gallon.

https://www.heatraesadia.com/en/product ... egaflo-eco
BTW other's have posted about "hot water heater". I have 2 water heaters, but they both heat cold water.
;-).

That's a so common bit of usage I think we can wear that? Technically it is not what is happening, but hot water comes out the end ;-).

Atgard
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Atgard » Fri Nov 10, 2017 10:47 am

I would not downsize. The savings I think would be minimal (and you could probably achieve the same by turning the temp down a little, keeping 40 gal at 125 deg instead of 30 gal at 140 deg or whatever), you might need the extra capacity sometimes, and I think it could negatively affect resale value with an under-sized unit.

If you're concerned about energy efficiency, I agree tankless may be the way to go. I don't want to go too far off-topic, but I've seen some differing opinions here in the thread, and it really depends on your individual situation. For example, what climate are you in, where is it located (near the breaker box?), and do you have enough capacity in your existing breaker box to add it in? (If not, the extra electrical work can make the job quite expensive.) For me, I'm in the south with warm incoming water, the water heater is near the breaker box in the garage, and the box had just enough space to add the new breakers required. So it was a very do-able installation with $100 of heavy gauge wire and a few new breakers. For someone else, needing to replace the breaker box and running thick wires all through the attic, it may not be worth it.

michaeljc70
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by michaeljc70 » Fri Nov 10, 2017 12:00 pm

I don't believe a blanket provides any benefit on newer hot water heaters. My hot water heater isn't even warm to the touch. They are very well insulated now. My parents had a blanket on their hot water heater 40 years ago though.

neilpilot
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by neilpilot » Fri Nov 10, 2017 12:36 pm

michaeljc70 wrote:
Fri Nov 10, 2017 12:00 pm
I don't believe a blanket provides any benefit on newer hot water heaters. My hot water heater isn't even warm to the touch. They are very well insulated now. My parents had a blanket on their hot water heater 40 years ago though.
You maybe correct, but I had 2 tanks replaced around 4 years ago and initially debated buying a blanket. They weren't warm to the touch. I decided to put a blanket on one of the 2 tanks. Just the other day I replaced some of the tape holding the blanket onto the tank. The space between the blanket and the tank was definitely warm. Maybe the loss isn't sufficient to increase the bare outer wall of the tank, but the blanket will definiely prevent some energy loss even on a newer tank.

Now I need to buy a blanket for that other tank.

My tanks are water heaters; maybe a HOT water heater like yours is different?

michaeljc70
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by michaeljc70 » Fri Nov 10, 2017 12:46 pm

neilpilot wrote:
Fri Nov 10, 2017 12:36 pm
michaeljc70 wrote:
Fri Nov 10, 2017 12:00 pm
I don't believe a blanket provides any benefit on newer hot water heaters. My hot water heater isn't even warm to the touch. They are very well insulated now. My parents had a blanket on their hot water heater 40 years ago though.
You maybe correct, but I had 2 tanks replaced around 4 years ago and initially debated buying a blanket. They weren't warm to the touch. I decided to put a blanket on one of the 2 tanks. Just the other day I replaced some of the tape holding the blanket onto the tank. The space between the blanket and the tank was definitely warm. Maybe the loss isn't sufficient to increase the bare outer wall of the tank, but the blanket will definiely prevent some energy loss even on a newer tank.

Now I need to buy a blanket for that other tank.

My tanks are water heaters; maybe a HOT water heater like yours is different?
I suppose the proper terminology is water heater or hot water tank....

neilpilot
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by neilpilot » Fri Nov 10, 2017 2:45 pm

Here’s a surprising comparison of a very popular AO Smith Signature water heaters, offered by my local Lowes. Take a look at the comparison of the SAME 30 vs 40 gallon unit:

30 gal Model #G6-T3030NV
  • Lowes’ Price $448
    Burner BTU rating 30k
    Annual energy delivery (therms) 202
    Expected annual energy cost $220
40 gal Model # G6-T4034NV
  • Lowes’ Price $424
    Burner BTU rating 34k
    Annual energy delivery (therms) 194
    Expected annual energy cost $212
If you figure a 6 year life for these units, and disregard installation cost which is likely the same, then the annual capital plus energy cost of the 30 gal unit is $295, and the 40 gal unit is $283. Maybe this isn't the model heater you would buy, and maybe the price and government energy estimate is off, but this sure begs the question of how the OP can expect to save $100/yr by downsizing.

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sunny_socal
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by sunny_socal » Sat Nov 11, 2017 10:05 am

neilpilot wrote:
Fri Nov 10, 2017 2:45 pm
Here’s a surprising comparison of a very popular AO Smith Signature water heaters, offered by my local Lowes. Take a look at the comparison of the SAME 30 vs 40 gallon unit:

30 gal Model #G6-T3030NV
  • Lowes’ Price $448
    Burner BTU rating 30k
    Annual energy delivery (therms) 202
    Expected annual energy cost $220
40 gal Model # G6-T4034NV
  • Lowes’ Price $424
    Burner BTU rating 34k
    Annual energy delivery (therms) 194
    Expected annual energy cost $212
If you figure a 6 year life for these units, and disregard installation cost which is likely the same, then the annual capital plus energy cost of the 30 gal unit is $295, and the 40 gal unit is $283. Maybe this isn't the model heater you would buy, and maybe the price and government energy estimate is off, but this sure begs the question of how the OP can expect to save $100/yr by downsizing.
Indeed. I posted similar stats from Home Depot with Rheem heaters but was promptly told that "common sense says that a bigger heater is less efficient!"

'Common sense' doesn't always apply to engineering. The bigger heater could have more insulation and it definitely has greater thermal mass. As others have pointed out it is likely more popular (rightly so), leading to lower price due to economies of scale.

Again, OP should stick with a 40gal. There is no reason whatsoever to downgrade.

neilpilot
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by neilpilot » Sat Nov 11, 2017 10:37 am

sunny_socal wrote:
Sat Nov 11, 2017 10:05 am
neilpilot wrote:
Fri Nov 10, 2017 2:45 pm
Here’s a surprising comparison of a very popular AO Smith Signature water heaters, offered by my local Lowes. Take a look at the comparison of the SAME 30 vs 40 gallon unit:

30 gal Model #G6-T3030NV
  • Lowes’ Price $448
    Burner BTU rating 30k
    Annual energy delivery (therms) 202
    Expected annual energy cost $220
40 gal Model # G6-T4034NV
  • Lowes’ Price $424
    Burner BTU rating 34k
    Annual energy delivery (therms) 194
    Expected annual energy cost $212
If you figure a 6 year life for these units, and disregard installation cost which is likely the same, then the annual capital plus energy cost of the 30 gal unit is $295, and the 40 gal unit is $283. Maybe this isn't the model heater you would buy, and maybe the price and government energy estimate is off, but this sure begs the question of how the OP can expect to save $100/yr by downsizing.
Indeed. I posted similar stats from Home Depot with Rheem heaters but was promptly told that "common sense says that a bigger heater is less efficient!"

'Common sense' doesn't always apply to engineering. The bigger heater could have more insulation and it definitely has greater thermal mass. As others have pointed out it is likely more popular (rightly so), leading to lower price due to economies of scale.

Again, OP should stick with a 40gal. There is no reason whatsoever to downgrade.
No, both units have the same insulation specs. The reason is that the bigger 40 gal unit has less surface area per gallon of capacity than the 30 gal unit. Therefore, the energy loss per gallon of capacity, even with the same insulation, is lower.

As a ChemE I hated thermodynamics in school, but I did retain a bit.

ncbill
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by ncbill » Sat Nov 11, 2017 10:58 am

No reason to change unless it isn't working for your family, i.e. regularly running out of hot water.

But you should check the sacrificial anode, as it likely needs replacement on a 10+ year old water heater.

rec7
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by rec7 » Sat Nov 11, 2017 1:08 pm

michaeljc70 wrote:
Fri Nov 10, 2017 10:30 am
rec7 wrote:
Thu Nov 09, 2017 10:16 am
I have a 40 and am going to a 30 once mine wears out. I can save about $100 a year. I should have done it a long time ago but I hate to get rid of something that is working. My father once ran a duplex on one 30 gallon tank. Remember the key is timing. Since he lived in the other half. He just noted the time they showered. Then went before or after them giving the tank time to recover.
Are you comparing apples to apples? In other words, a new 40 gallon vs a new 30 gallon?

My 18 year old 50 gallon inefficient water heater says it cost $168 a year to run. That's why it seems unlikely moving from a 40 to 30 gallon would save $100 a year. But maybe you live somewhere with high gas prices.
That sticker might be old. Remember gas has gone up in the last 18 years. The new ones I have seen range from $200 to $300
Disclaimer: You might lose money doing anything I say. Although that was not my intent. | Favorite song: Sometimes He Whispers Jay Parrack

rec7
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by rec7 » Sat Nov 11, 2017 1:12 pm

Disclaimer: You might lose money doing anything I say. Although that was not my intent. | Favorite song: Sometimes He Whispers Jay Parrack

Valuethinker
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Valuethinker » Sat Nov 11, 2017 1:22 pm

michaeljc70 wrote:
Fri Nov 10, 2017 12:00 pm
I don't believe a blanket provides any benefit on newer hot water heaters. My hot water heater isn't even warm to the touch. They are very well insulated now. My parents had a blanket on their hot water heater 40 years ago though.
This is my experience with our super duper insulated tank -- the factory installed insulation is so good that you really can't feel any heat loss on the surface.

Note that the *feet* of the tank, if floor mounted, are a significant cold bridging point at this level of insulation, so best in breed also has a thermal break on the base of the tank (or mountings that fit to the wall brackets if wall mounted).

Main issue is that presumably the dimensions have increased because of the better insulation?

If OP can get a better insulated tank that is 40 gallons that is still the way to go, to my mind.

Saving$
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Saving$ » Sat Nov 11, 2017 2:31 pm

WH facts
- If your old WH has a yellow energy sticker indicating how much it costs to run, it is based on assumed quantity of usage and assumed cost of energy. Figure out how much you use, and your current cost of energy.

- Factors contributing to how much hot water you get from a tank WH are size of WH tank, RECOVERY RATE of the individual WH (have not seen this mentioned and it is important), age of WH (older ones produce less HW than newer ones, due to deterioration of the elements), entering temperature of cold water. In the winter cold water enters at lower temp than in summer so your WH takes longer to heat that entering water. But the entering water mixes with all the water in the tank, tempering it all.

Tankless
= Are rated by flow - some will provide enough HW for only 1 shower, higher powered ones for multiple showers
- All (gas and electric) require power to operate so if power goes out you have no hot water
- Can sometimes be expensive to retrofit
- Usually do not "pay for themselves" after the cost to purchase, install and operate vs traditional tank type
+ Save space
+ Can provide endless hot water (if you have many family members or guests)
- Can provide endless hot water (if you have teenagers your water bill may increase)

Tank
= Are rated by tank size, recovery rate and efficiency
= The most cost effective are the standard sizes, recovery rates and efficiencies. They are bought in bulk. So a 40 gal may be less expensive than a 30, and two 40's less expensive than one 80...
- Take more space than tankless. Newer ones may be larger than the older units they replace because the newer ones have more insulation
+ Electric maintains hot water in tank for a period of time (+/-24 hrs) if the power goes out; Atmospherically vented gas or direct vent non powered gas will continue to operate if the power goes out.
+ Are usually less expensive to purchase and install unless your area subsidizes tankless

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rocket354
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by rocket354 » Sat Nov 11, 2017 3:46 pm

rec7 wrote:
Sat Nov 11, 2017 1:08 pm
michaeljc70 wrote:
Fri Nov 10, 2017 10:30 am
rec7 wrote:
Thu Nov 09, 2017 10:16 am
I have a 40 and am going to a 30 once mine wears out. I can save about $100 a year. I should have done it a long time ago but I hate to get rid of something that is working. My father once ran a duplex on one 30 gallon tank. Remember the key is timing. Since he lived in the other half. He just noted the time they showered. Then went before or after them giving the tank time to recover.
Are you comparing apples to apples? In other words, a new 40 gallon vs a new 30 gallon?

My 18 year old 50 gallon inefficient water heater says it cost $168 a year to run. That's why it seems unlikely moving from a 40 to 30 gallon would save $100 a year. But maybe you live somewhere with high gas prices.
That sticker might be old. Remember gas has gone up in the last 18 years. The new ones I have seen range from $200 to $300
This makes sense. In the summer, the only thing using gas in my home is the water heater. I pay $19-20/month like clockwork from May - September.

quantAndHold
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by quantAndHold » Sat Nov 11, 2017 4:08 pm

rec7 wrote:
Fri Nov 10, 2017 10:16 am
quantAndHold wrote:
Fri Nov 10, 2017 12:31 am
rec7 wrote:
Thu Nov 09, 2017 10:16 am
I have a 40 and am going to a 30 once mine wears out. I can save about $100 a year. I should have done it a long time ago but I hate to get rid of something that is working. My father once ran a duplex on one 30 gallon tank. Remember the key is timing. Since he lived in the other half. He just noted the time they showered. Then went before or after them giving the tank time to recover.
I assume you have an electric hot water heater? My 15 year old, 40 gallon gas water heater only costs us about $9/month to run (2 adults). It would be very difficult to save $100 a year on hot water unless we just stopped using hot water completely.
Ours is natural gas. I got those numbers off the yellow energy stickers.
I have no idea what our yellow sticker says. We went to a workshop that our local utility put on about installing a solar hot water system. They told us how to calculate out hot water usage (which I forget now, because it was several years ago). We ended up not doing solar because we were literally only using $9/month in hot water, and the payback period for a new system was somewhere around 35 years.

It can’t be much more than $9 even now, because our summer gas bills are only $15-18/month, and all of our appliances are gas.

mnnice
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by mnnice » Sat Nov 11, 2017 9:34 pm

tesuzuki2002 wrote:
Thu Nov 09, 2017 3:59 pm
Speaking of water heaters.... what is the recommended time to replace them. I have one that is 13 years old. Still works fine.. Should I consider replacing?
When they die (which usually means leaking.) Not sure why you would replace a working natural gas heater. The technology and efficiency haven’t changed very much in recent years. I do know the life of one is shorter if your water hard.

michaeljc70
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by michaeljc70 » Sat Nov 11, 2017 10:15 pm

rec7 wrote:
Sat Nov 11, 2017 1:08 pm
michaeljc70 wrote:
Fri Nov 10, 2017 10:30 am
rec7 wrote:
Thu Nov 09, 2017 10:16 am
I have a 40 and am going to a 30 once mine wears out. I can save about $100 a year. I should have done it a long time ago but I hate to get rid of something that is working. My father once ran a duplex on one 30 gallon tank. Remember the key is timing. Since he lived in the other half. He just noted the time they showered. Then went before or after them giving the tank time to recover.
Are you comparing apples to apples? In other words, a new 40 gallon vs a new 30 gallon?

My 18 year old 50 gallon inefficient water heater says it cost $168 a year to run. That's why it seems unlikely moving from a 40 to 30 gallon would save $100 a year. But maybe you live somewhere with high gas prices.
That sticker might be old. Remember gas has gone up in the last 18 years. The new ones I have seen range from $200 to $300
So, I looked at my bill for July since that would not include any furnace heat. That would include my water heater and stove. I paid a $2.63 distribution charge and a $5.21 gas charge. I used 13.5 therms. Now, I guess it depends what you count. There is a $33 customer charge which is charged even if I use no gas. Then there are taxes. But I really used around $8 in natural gas. I have People's Gas in Illinois.

ncbill
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by ncbill » Sat Nov 11, 2017 10:40 pm

michaeljc70 wrote:
Sat Nov 11, 2017 10:15 pm
rec7 wrote:
Sat Nov 11, 2017 1:08 pm
michaeljc70 wrote:
Fri Nov 10, 2017 10:30 am
rec7 wrote:
Thu Nov 09, 2017 10:16 am
I have a 40 and am going to a 30 once mine wears out. I can save about $100 a year. I should have done it a long time ago but I hate to get rid of something that is working. My father once ran a duplex on one 30 gallon tank. Remember the key is timing. Since he lived in the other half. He just noted the time they showered. Then went before or after them giving the tank time to recover.
Are you comparing apples to apples? In other words, a new 40 gallon vs a new 30 gallon?

My 18 year old 50 gallon inefficient water heater says it cost $168 a year to run. That's why it seems unlikely moving from a 40 to 30 gallon would save $100 a year. But maybe you live somewhere with high gas prices.
That sticker might be old. Remember gas has gone up in the last 18 years. The new ones I have seen range from $200 to $300
So, I looked at my bill for July since that would not include any furnace heat. That would include my water heater and stove. I paid a $2.63 distribution charge and a $5.21 gas charge. I used 13.5 therms. Now, I guess it depends what you count. There is a $33 customer charge which is charged even if I use no gas. Then there are taxes. But I really used around $8 in natural gas. I have People's Gas in Illinois.
Is that per month?

I thought we were getting robbed at $10/month meter fee (actual gas use only $6-$8/month to heat water)

michaeljc70
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by michaeljc70 » Sat Nov 11, 2017 10:44 pm

ncbill wrote:
Sat Nov 11, 2017 10:40 pm
michaeljc70 wrote:
Sat Nov 11, 2017 10:15 pm
rec7 wrote:
Sat Nov 11, 2017 1:08 pm
michaeljc70 wrote:
Fri Nov 10, 2017 10:30 am
rec7 wrote:
Thu Nov 09, 2017 10:16 am
I have a 40 and am going to a 30 once mine wears out. I can save about $100 a year. I should have done it a long time ago but I hate to get rid of something that is working. My father once ran a duplex on one 30 gallon tank. Remember the key is timing. Since he lived in the other half. He just noted the time they showered. Then went before or after them giving the tank time to recover.
Are you comparing apples to apples? In other words, a new 40 gallon vs a new 30 gallon?

My 18 year old 50 gallon inefficient water heater says it cost $168 a year to run. That's why it seems unlikely moving from a 40 to 30 gallon would save $100 a year. But maybe you live somewhere with high gas prices.
That sticker might be old. Remember gas has gone up in the last 18 years. The new ones I have seen range from $200 to $300
So, I looked at my bill for July since that would not include any furnace heat. That would include my water heater and stove. I paid a $2.63 distribution charge and a $5.21 gas charge. I used 13.5 therms. Now, I guess it depends what you count. There is a $33 customer charge which is charged even if I use no gas. Then there are taxes. But I really used around $8 in natural gas. I have People's Gas in Illinois.

Is that per month?

I thought we were getting robbed at $10/month meter fee (actual gas use only $6-$8/month to heat water)

Yes-per month. $8 in gas costs me $55 here in Chicago. The taxes are crazy on every utility bill.

I think that changed recently. My whole bill in the summer was around $35/mo. I think they jacked up the customer charge and lowered the rate.

quantAndHold
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by quantAndHold » Sun Nov 12, 2017 11:07 am

I don’t know what rate they use when they create those yellow stickers, but the price of natural gas is roughly 1/4 what it was 10 years ago. So it seems likely that the yellow stickers are not an accurate representation of what you would actually pay.

bob60014
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by bob60014 » Sun Nov 12, 2017 11:21 am

Those yellow sticker GUIDES are like the EPA MPG figures on vehicles. As such, YMMV!! :)

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Toons
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Toons » Sun Nov 12, 2017 11:24 am

jerryk68 wrote:
Fri Nov 10, 2017 8:15 am
Many years ago went from an electric 80 or 85 gal tank to a 40 gal tank without any trouble. Just do the mental math. For me it was usually 1 shower at 6AM, 2 showers at 7AM and one at 9AM. In between showers the tank recovered. Laundry and dishwasher usually ran at other times. I never needed to adjust the temperature of the water and never ran out of hot water. Why pay for a large tank when it's not really needed?

+1
I tend to agree :happy
"One does not accumulate but eliminate. It is not daily increase but daily decrease. The height of cultivation always runs to simplicity" –Bruce Lee

neilpilot
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by neilpilot » Sun Nov 12, 2017 12:57 pm

quantAndHold wrote:
Sun Nov 12, 2017 11:07 am
I don’t know what rate they use when they create those yellow stickers, but the price of natural gas is roughly 1/4 what it was 10 years ago. So it seems likely that the yellow stickers are not an accurate representation of what you would actually pay.
Average residential price of natural gas in Aug 2017 was $18.09 per thousand cu ft. In Aug 2007 it was $16.71. So the price is 8% higher than it was 10 years ago. Your statement isn't even remotely close to reality. Opinion is one thing, but I find it amusing how opinions appear as "facts" on these threads.

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm

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Watty
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Watty » Sun Nov 12, 2017 1:32 pm

mnnice wrote:
Sat Nov 11, 2017 9:34 pm
When they die (which usually means leaking.) Not sure why you would replace a working natural gas heater.
When they fail they can cause significant damage especially if you are not home when they fail. You then have to get it replaced in a hurry which can be inconvenient and more expensive.

Two people in our neighborhood have had this happen recently. I am having a 13 year old one replaced this week week as a preventative measure.

Spread over 13 years the replacement cost is well less than $100 a year and squeezing a few more years would not lower the annualized cost a lot.

quantAndHold
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by quantAndHold » Sun Nov 12, 2017 1:44 pm

I got curious and looked at my yellow sticker and at my bill.

The yellow sticker on my “nothing special” 40 gallon hot water heater installed in 2013 says estimated annual cost of $309 based on a price of $1.21/therm. Which means they’re estimating that we’ll use 20 therms every month. Google says that they base this on 64 gallons per day usage. 2 adults would have a hard time using this much hot water.

My actual bills over the past 6 (non-heating) months show average usage of 12 therms per month for all gas appliances combined, at an average price of $1.31/therm, or $15/month for everything. I was able to break it down using our travel schedule. When we’re traveling, we use roughly 1.5 therms ($1.90) per week, presumably all on keeping the hot water in the tank hot.

So, a fairly ordinary 40 gallon tank is costing $7.50/month. I would guess a 30 gallon tank would cost $6-7.

There’s frugal, and there’s making your life less comfortable without any real benefit.

Now, the month we used the clothes dryer before we got the clothesline fixed...completely different story. If you really want to save money on gas, get a clothesline and stop using the dryer. Our gas bill more than doubled that month.

quantAndHold
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by quantAndHold » Sun Nov 12, 2017 1:45 pm

neilpilot wrote:
Sun Nov 12, 2017 12:57 pm
quantAndHold wrote:
Sun Nov 12, 2017 11:07 am
I don’t know what rate they use when they create those yellow stickers, but the price of natural gas is roughly 1/4 what it was 10 years ago. So it seems likely that the yellow stickers are not an accurate representation of what you would actually pay.
Average residential price of natural gas in Aug 2017 was $18.09 per thousand cu ft. In Aug 2007 it was $16.71. So the price is 8% higher than it was 10 years ago. Your statement isn't even remotely close to reality. Opinion is one thing, but I find it amusing how opinions appear as "facts" on these threads.

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm

http://www.macrotrends.net/2478/natural ... ical-chart

Chip
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Chip » Sun Nov 12, 2017 2:10 pm

neilpilot wrote:
Sun Nov 12, 2017 12:57 pm
Average residential price of natural gas in Aug 2017 was $18.09 per thousand cu ft. In Aug 2007 it was $16.71. So the price is 8% higher than it was 10 years ago. Your statement isn't even remotely close to reality. Opinion is one thing, but I find it amusing how opinions appear as "facts" on these threads.

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm
I think the source you're quoting is flawed for the purposes of this discussion. The notes say that "Published residential, commercial, and industrial prices are considered to be total prices paid by end-users per thousand cubic feet of natural gas in the respective sectors, inclusive of all tax, delivery, commodity, demand and other charges."

I interpret this to mean that fixed charges associated with residential accounts are included (like the $41 a month I pay). And I would speculate that is why the prices shown ramp up so much in the summer vs. the "Citygate" prices. If you look at the data on that site for 2017 since March, you can see the residential price nearly doubled from March to August while the Citygate price only went up about 15%.

The important thing for this discussion is the marginal cost of gas. In August I used 10 CCF of gas. I paid $46.68 for it, or 4.67 per CCF. But if I had used 20 CCF I would have only paid a total of about $52.30. My marginal cost was about $.56/CCF.

But 10 years ago, before natgas deregulation came to my state, fixed charges were only $6 a month. But the marginal cost of a CCF was nearly $1.30, as some of those fixed charges were loaded into the price of a CCF by the utility monopoly. So from that perspective, gas prices are indeed half of what they were 10 years ago. And that perspective is one that should be used in this evaluation.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by RustyShackleford » Sun Nov 12, 2017 2:34 pm

ThatGuy wrote:
Thu Nov 09, 2017 11:52 am
... it is actually more efficient to go with a bigger unit, as the surface area to volume ratio is much smaller.
It depends on what you mean by "efficient". For the question the OP is asking, the thing to look at is how much energy will he save with the smaller tank, and this depends solely on the surface area. Since volume goes as the cube of linear dimension and surface area as the square, the surface area will not increase/decrease at the same "rate" as volume. So even though a 30 gallon tank is 0.75 times the volume of the 40 gallon tank, the surface area is about 0.83 that of the 30 gallon tank (assuming they are the same diameter/height ratio, a reasonable approximation).

But this is all academic. The real question is, how much less heat will be wasted with the 30 gallon (or how much more heat will be wasted with the 50 gallon). Simply calculate the surface area of the tank (in sq-ft), multiply this by the temperature differential (in degrees Fahrenheit between the hot water and the ambient), and divide that by the R-value of the tank insulation. This will tell you how many btu/hr are lost thru the tank's walls, and divide that by 3.4 to get watts. Then you can simply say that that 30 gallon tank is saving you (or the 50 gallon tank is costing you) the same energy as having an X watt light bulb burning all the time. Multiply that by the number of hours in a month and your cost of electricity if you like (or whatever the corresponding calculation is for gas).

The simple fact is, this will be very small compared to the energy that flows out of your hot water faucet. And probably even compared to the energy lost in "stranded" hot water - that which is left in the hot water pipes, to uselessly cool off, after you turn off your hot water faucet. That latter, especially, coupled with the extreme efficiency of modern storage-tank electric hot-water heaters, is why I think tankless are a bad deal (because of their far greater purchase, installation, and maintenance costs); in fact, they can increase the biggest energy cost of your hot-water system, the hot water flowing out the faucet, because your (or you teenagers') ability to take very long showers.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by neilpilot » Sun Nov 12, 2017 2:42 pm

quantAndHold wrote:
Sun Nov 12, 2017 1:45 pm
neilpilot wrote:
Sun Nov 12, 2017 12:57 pm
quantAndHold wrote:
Sun Nov 12, 2017 11:07 am
I don’t know what rate they use when they create those yellow stickers, but the price of natural gas is roughly 1/4 what it was 10 years ago. So it seems likely that the yellow stickers are not an accurate representation of what you would actually pay.
Average residential price of natural gas in Aug 2017 was $18.09 per thousand cu ft. In Aug 2007 it was $16.71. So the price is 8% higher than it was 10 years ago. Your statement isn't even remotely close to reality. Opinion is one thing, but I find it amusing how opinions appear as "facts" on these threads.

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm

http://www.macrotrends.net/2478/natural ... ical-chart
Your link shows "Henry Hub" pricing, which is wholesale price at the distribution hub. It does not reflect the price a homeowner pays for NG.

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Watty
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Watty » Sun Nov 12, 2017 2:52 pm

On the energy efficiency you also have to consider what happens to the lost energy.

Some of it goes out with the exhaust but our water heater is in the basement below the living area so any lost energy goes into keeping our house warm so it would reduce our home heating costs in the winter time. That works against you during the AC season but if you live in an area where AC is not used extensively then that might not be a big factor.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by quantAndHold » Sun Nov 12, 2017 3:45 pm

neilpilot wrote:
Sun Nov 12, 2017 2:42 pm
quantAndHold wrote:
Sun Nov 12, 2017 1:45 pm
neilpilot wrote:
Sun Nov 12, 2017 12:57 pm
quantAndHold wrote:
Sun Nov 12, 2017 11:07 am
I don’t know what rate they use when they create those yellow stickers, but the price of natural gas is roughly 1/4 what it was 10 years ago. So it seems likely that the yellow stickers are not an accurate representation of what you would actually pay.
Average residential price of natural gas in Aug 2017 was $18.09 per thousand cu ft. In Aug 2007 it was $16.71. So the price is 8% higher than it was 10 years ago. Your statement isn't even remotely close to reality. Opinion is one thing, but I find it amusing how opinions appear as "facts" on these threads.

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm

http://www.macrotrends.net/2478/natural ... ical-chart
Your link shows "Henry Hub" pricing, which is wholesale price at the distribution hub. It does not reflect the price a homeowner pays for NG.
Possibly, but your own chart doesn’t agree with your statement that the price is 8% higher than 10 years ago, only that your cherry picked month is 8% higher. In 10 of the most recent 12 months on your chart, the price is lower than it was 10 years ago.

My actual point is still valid. The yellow sticker is not an accurate picture of reality.

neilpilot
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by neilpilot » Sun Nov 12, 2017 4:25 pm

quantAndHold wrote:
Sun Nov 12, 2017 3:45 pm
neilpilot wrote:
Sun Nov 12, 2017 2:42 pm
quantAndHold wrote:
Sun Nov 12, 2017 1:45 pm
neilpilot wrote:
Sun Nov 12, 2017 12:57 pm
quantAndHold wrote:
Sun Nov 12, 2017 11:07 am
I don’t know what rate they use when they create those yellow stickers, but the price of natural gas is roughly 1/4 what it was 10 years ago. So it seems likely that the yellow stickers are not an accurate representation of what you would actually pay.
Average residential price of natural gas in Aug 2017 was $18.09 per thousand cu ft. In Aug 2007 it was $16.71. So the price is 8% higher than it was 10 years ago. Your statement isn't even remotely close to reality. Opinion is one thing, but I find it amusing how opinions appear as "facts" on these threads.

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm

http://www.macrotrends.net/2478/natural ... ical-chart
Your link shows "Henry Hub" pricing, which is wholesale price at the distribution hub. It does not reflect the price a homeowner pays for NG.
Possibly, but your own chart doesn’t agree with your statement that the price is 8% higher than 10 years ago, only that your cherry picked month is 8% higher. In 10 of the most recent 12 months on your chart, the price is lower than it was 10 years ago.

My actual point is still valid. The yellow sticker is not an accurate picture of reality.
I guess we could get into a pissing contest, but there's no point in arguing. NG retail pricing almost always fluctuates seasonally every year. I could have picked any of the months from 2017 and 10 years with the same result, but I simply picked the most recent data for 2017. I reacted to your post because you said "the price of natural gas is roughly 1/4 what it was 10 years ago". Well with 2017 pricing YTD ranging from $9.38-18.09, then the price 10 years ago would have needed to be at least $37.50 for your statement to be correct. But 2007 monthly average prices ranged from $12.17-16.71. You can argue the facts, but wholesale pricing isn't useful data.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by meebers » Sun Nov 12, 2017 9:12 pm

I am just looking at my NG bill. Only device using NG is the water heater, my bill says, 33 days, "Therms Used" = 12.57, "Cost per Therm" = .77000 and the charge is = $9.68. another line below that says "Therms used" - 12.57 and "Cost per Therm" - .33500 and the charge is $4.21. Total for the month is $9.68 + $4.21 = $13.89. Second entry might be a variable fuel surcharge??

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Valuethinker » Mon Nov 13, 2017 4:13 am

neilpilot wrote:
Sun Nov 12, 2017 4:25 pm
quantAndHold wrote:
Sun Nov 12, 2017 3:45 pm
You can argue the facts, but wholesale pricing isn't useful data.
This is the nub of it.

You can't use wholesale price data to talk about retail prices. US wholesale natural gas price went from something like $16 to $2.50 (I remember the price, but not the units used). So yes, say 1/7th.

EIA publishes average retail prices

https://www.eia.gov/dnav/ng/ng_pri_sum_ ... DMcf_m.htm

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm

historic US averages, but the State by State swings are much greater. Month by month data

2006 14.92 13.98 13.17 13.27 14.41 15.07 15.72 16.18 15.71 12.51 12.45 12.53



2016 8.28 8.36 9.19 9.65 11.62 14.43 16.55 17.60 16.78 13.74 10.77 9.06

They have dropped, but by less than the glut at the wholesale level might lead you to believe.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Valuethinker » Mon Nov 13, 2017 4:14 am

meebers wrote:
Sun Nov 12, 2017 9:12 pm
I am just looking at my NG bill. Only device using NG is the water heater, my bill says, 33 days, "Therms Used" = 12.57, "Cost per Therm" = .77000 and the charge is = $9.68. another line below that says "Therms used" - 12.57 and "Cost per Therm" - .33500 and the charge is $4.21. Total for the month is $9.68 + $4.21 = $13.89. Second entry might be a variable fuel surcharge??
There might be a Transmission charge? I.e. a charge imposed on your gas supplier for using the main pipelines, which for regulatory reasons is separately broken out?

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by Chip » Mon Nov 13, 2017 6:20 am

Valuethinker wrote:
Mon Nov 13, 2017 4:13 am
neilpilot wrote:
Sun Nov 12, 2017 4:25 pm
quantAndHold wrote:
Sun Nov 12, 2017 3:45 pm
You can argue the facts, but wholesale pricing isn't useful data.
This is the nub of it.

You can't use wholesale price data to talk about retail prices. US wholesale natural gas price went from something like $16 to $2.50 (I remember the price, but not the units used). So yes, say 1/7th.

EIA publishes average retail prices

https://www.eia.gov/dnav/ng/ng_pri_sum_ ... DMcf_m.htm

https://www.eia.gov/dnav/ng/hist/n3010us3m.htm
Those EIA retail prices are NOT valid for this discussion, for the reasons I listed above. It appears that my $41/month fixed charge is included in my "cost per CCF" reported by the EIA in the top link you gave. That causes my retail "gas price" to vary from ~$4.70/CCF in the summer to ~$0.80 in the winter, when those fixed charges are spread over much higher usage.

My marginal cost of a CCF, which is the relevant bit of data for any energy-saving discussion, varied from about $0.52 - $0.58/CCF during the same period.

You can verify this for yourself. The EIA data come from surveys of gas utilities on Form EIA-857. Click on Definitions, Sources & Notes above the table you linked. This tells you that residential price data come from EIA-857. Under Explanatory Notes on that page you'll see the quote I posted above:

"Published residential, commercial, and industrial prices are considered to be total prices paid by end-users per thousand cubic feet of natural gas in the respective sectors, inclusive of all tax, delivery, commodity, demand and other charges."

If that's not enough, visit the instructions for filling out EIA-857, where you'll find this:

"Revenue: Revenue should include gross revenues, all system charges or minimum bill amounts,commodity charges, taxes, surcharges, adjustments, and other charges billed for the gas delivered."

If you look at EIA-857 itself, the utility provides only the following data: Number of customers, volume delivered, revenue.

With that little data it is clear that EIA is calculating that "retail gas price" as revenue/volume. Which often (always?) has NO bearing on the marginal cost of gas.

I think that quantAndHold's use of wholesale prices would be much more representative of actual retail consumer marginal cost trends than these useless EIA numbers.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by dodgy55 » Mon Nov 13, 2017 9:11 am

As the original author of this post I must admit I have come full circle. As suggested in other postings, I looked at my gas bill for the summer months and noted an average monthly charge for gas supply for HW of around $8. The delivery charge was another $25. At $8 per month for gas supply, any savings by going to a smaller tank would be minor. The delivery charge would be the same for a 40 gal or 30 gal. Other postings got me to thinking about installing a whole-house tankless heater. But given the installation costs this would not make sense. Want to thank all BH's who weighed in on this matter, very informative and helpful in arriving at which path to choose.
Fond memories are the best investment

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by hudson » Mon Nov 13, 2017 9:28 am

dodgy55 wrote:
Mon Nov 13, 2017 9:11 am
As the original author of this post I must admit I have come full circle. As suggested in other postings, I looked at my gas bill for the summer months and noted an average monthly charge for gas supply for HW of around $8. The delivery charge was another $25. At $8 per month for gas supply, any savings by going to a smaller tank would be minor. The delivery charge would be the same for a 40 gal or 30 gal. Other postings got me to thinking about installing a whole-house tankless heater. But given the installation costs this would not make sense. Want to thank all BH's who weighed in on this matter, very informative and helpful in arriving at which path to choose.
Thanks for sharing your solution!
If my water heater made it 12 years, I'd be getting quotes for replacement. I understand the average lifespan is 8-12 years. I'd make sure that all of the good stuff was in place...a drip pan with an outside drain...a leak warning system, an expansion tank on top, a ball valve shut-off valve...etc.

My research years ago found that tankless water heaters shouldn't be considered unless you have natural gas.

A 2013 Boglehead discussion on replacing water heaters: viewtopic.php?f=11&t=129263&hilit=water+heater
Last edited by hudson on Mon Nov 13, 2017 9:47 am, edited 1 time in total.

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DaftInvestor
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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by DaftInvestor » Mon Nov 13, 2017 9:36 am

I've only always gone in only one direction - UP.
Unless you are really struggling financially and saving a few dollars a month will make a big difference to you I certainly wouldn't downsize.
Do you want to time out intervals between showers? Or not be able to take one if the dishwasher just finishing running?
That's been my experience with 30 Gal. tanks. Its minor savings for a huge inconvenience in my opinion going with a smaller tank.
The first thing we've done when buying houses is replace the hot water heater with a bigger one.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by neilpilot » Mon Nov 13, 2017 10:01 am

DaftInvestor wrote:
Mon Nov 13, 2017 9:36 am
I've only always gone in only one direction - UP.
Unless you are really struggling financially and saving a few dollars a month will make a big difference to you I certainly wouldn't downsize.
Do you want to time out intervals between showers? Or not be able to take one if the dishwasher just finishing running?
That's been my experience with 30 Gal. tanks. Its minor savings for a huge inconvenience in my opinion going with a smaller tank.
The first thing we've done when buying houses is replace the hot water heater with a bigger one.
Agree with one additional. You state "Its minor savings for a huge inconvenience in my opinion going with a smaller tank." I contend there is likely no savings.

Based on some of the numbers in this thread, a 30 gal tank might cost MORE to purchase and to operate than a comparable 40 gal unit.

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Re: Worth changing 40 gal. to 30gal. hot water tank?

Post by ryuns » Mon Nov 13, 2017 5:12 pm

If one is really interested in saving on the utility bill, the size of your water heater is pretty low on the list of things to consider (and may not help at all, as others note. Reduing the amount of hot water you actually use is a lot more effective. Many folks disagree, but I actually found downsizing from a 2.5 gpm showerhead to 1.5 to be pretty painless. It takes my wife a little longer to rinse her hair, but not a huge deal. Saves a pile of money (and I never worry about running out of hot water because I'm draining the tank far more slowly.)
An inconvenience is only an adventure wrongly considered; an adventure is an inconvenience rightly considered. -- GK Chesterton

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