Replace gas water heater with electric?

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gd
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Replace gas water heater with electric?

Post by gd » Thu Mar 02, 2017 1:16 pm

I'm trying to replace a conventional chimney vent natural gas water heater. For various reasons, I want to switch to just about anything else to get away from the chimney. But plastic venting is difficult to place in my house, and although I had first not even considered electric due to its reputation of being more expensive than gas I was surprised to discover that electric hybrids appear as economical to operate as direct or power vent gas, with utility rates of $1.40/therm and $.197/kWh. It'll be in a basement with temps of 53 to 65F. High efficiency tankless gas is even cheaper, but even more difficult to install due to placement of 2 vent pipes. I'm not worrying about purchase and installation costs at this point, there are other practical issues, particularly installation, that are more important.

Can those knowledgeable about water heaters confirm that electric hybrids are operationally competitive with gas tanks in real life? Can anyone give me a sense of how noisy they are in heat pump mode (this is in unfinished basement below living area), and any other negatives of switching from gas to electric? Our usage is light and well distributed, and power outages prevent much water usage due to sewage pump so not a big factor.

HIgh efficiency tankless might be a remote possibility if my plumber gets creative, but I wonder about the warmup time. One of my goals is to get the heater closer to the faucet, to speed up hot water availability (without circulation loop, TIA :D ). In practice, how long from water flow to actual hot water out of the heater box? I read 15-20 secs, but have seen claims of longer.

John Z
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Re: Replace gas water heater with electric?

Post by John Z » Thu Mar 02, 2017 3:11 pm

Not knowledgeable about hybrid water heaters but asking if you considered additional electrical installation costs of a 220 volt line and whether your current breaker box has room for a 220 volt line.

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lthenderson
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Re: Replace gas water heater with electric?

Post by lthenderson » Thu Mar 02, 2017 3:20 pm

gd wrote:For various reasons, I want to switch to just about anything else to get away from the chimney.
Just curious as to why you want to get rid of a chimney vent? My last go around I almost went with a forced vent but since electrical outages are fairly common around here, I stuck with the gas chimney vent to keep us in hot water even during an outage.

Also, if you haven't already, I would consult with a plumber about your situation. They deal with this day in and day out and have pretty creative solutions when people such as myself think something isn't possible.

wilked
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Re: Replace gas water heater with electric?

Post by wilked » Thu Mar 02, 2017 3:22 pm

what's wrong with the chimney?

Hankscorpio_84
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Re: Replace gas water heater with electric?

Post by Hankscorpio_84 » Thu Mar 02, 2017 3:24 pm

I would suggest doing more reading if you are seriously considering the tankless. Most that I am familiar with have small tubes as a part of the heat exchange system. These small tubes can be easily clogged and require more cleaning (like annually, more if you have hard water) than a traditional tank style heater.

Here is a site that has more information on water heaters than you can dream of, but is fairly well organized to find what you need to know:

http://www.waterheaterrescue.com/Longev ... asics.html

In my opinion, simplicity if your best friend. The electric costs less up front and is easiest to install, but costs more per month to use (a factor that you have control over by how much water you use).

Gas units are technically superior to electric, but cost more to install due to venting and plumbing the gas line. It also sounds like you may need to get creative with the venting, which only increases the chances of issues.

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dratkinson
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Re: Replace gas water heater with electric?

Post by dratkinson » Thu Mar 02, 2017 5:39 pm

lthenderson wrote:
gd wrote:For various reasons, I want to switch to just about anything else to get away from the chimney.
Just curious as to why you want to get rid of a chimney vent? My last go around I almost went with a forced vent but since electrical outages are fairly common around here, I stuck with the gas chimney vent to keep us in hot water even during an outage.

Also, if you haven't already, I would consult with a plumber about your situation. They deal with this day in and day out and have pretty creative solutions when people such as myself think something isn't possible.
+1 A standing pilot light, vertical vent WH is one less thing to worry about during an outage. I keep one for that major reason (1).

+1 Ask a trusted* plumbing business for advice. But as you already have the vertical vent and NG line, replacing with the same type would probably be your cheapest option. (* Ask for recommendations from your neighbors who've lived in the area for a long time; that's how I found one that I trust. (Avoid plumbers who advertise with sticky magnets on the front of phone books. Been there, done that, never again.) My chosen plumber demonstrated that if I went with a new tankless WH, that it would required >75-years to break even, and they (nor I) don't last that long. So my cheapest option is to stay with the type I've got (2).)

So, (1) hot water during an outage + (2) it's probably your cheapest replacement option, are two good reasons to stay with the type you have.
d.r.a, not dr.a. | I'm a novice investor, you are forewarned.

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dm200
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Re: Replace gas water heater with electric?

Post by dm200 » Thu Mar 02, 2017 5:51 pm

1. Do you really need a "chimney" for a gas water heater?

2. The recovery rate of a gas water heater (same size tank) is much quicker than electric

3. Gas is probably less expensive

dpc
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Re: Replace gas water heater with electric?

Post by dpc » Thu Mar 02, 2017 6:37 pm

I'm not worrying about purchase and installation cost
But you're worried about energy costs? That seems illogical. Money is money.

I'd prefer gas, especially since you have everything in place. Replacement should be straightforward. It will be cheaper in terms of energy costs.

That said, if you want to convert to electric, the energy cost premium isn't that big an issue, IMO. Millions of people use electric water heaters - many have no choice. You will need a 240 V circuit to the water heater. But no vent! 8-)

If you're considering tankless, I'd do a lot of research. There is a lag in getting hot water every time you turn on the tap. It takes a lot of getting used to.

Go with whatever makes you happy.
"Worrying is like paying interest on a debt that you might never owe" -- Will Rogers

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Re: Replace gas water heater with electric?

Post by Inframan4712 » Thu Mar 02, 2017 7:10 pm

I have natural gas water heater and natural gas furnace. My neighbor has all electric. We have the same size family, same size house.

My energy bills are literally one-half as in 50% of his.

And our electricity here is 11-15 cents/kwh.

Edited to add he has a small pool, but still.

In the summer, when not using the furnace so just heating water, my gas bill is $18. And $10 of that is a fixed "facilities charge."

ralph124cf
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Re: Replace gas water heater with electric?

Post by ralph124cf » Thu Mar 02, 2017 7:49 pm

I have been told by a local handyman (experienced, but not a licensed plumber) that natural vent water heaters may no longer be sold. Does anybody have actual knowledge about this? Perhaps it varies by locality, the plumbers union in this area has a lot of influence.

Ralph

bbqguru
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Re: Replace gas water heater with electric?

Post by bbqguru » Thu Mar 02, 2017 8:19 pm

How tall is your chimney? If you're wanting to get away from using the chimney as the actual vent, there are some tankless models that you can use your chimney as a chase. They vent with flexible pipe and you just drop it down from the top and hook to the water heater. If size of your chimney is an issue, Navien makes a tankless heater that uses 2" PVC for venting. Most traditional power-vent water heaters can use 2" venting as well.

Most tankless gas heaters can pull room air if the area is big enough so you only need one vent pipe. If you've got a gas heater now that is single vented, chances are the tankless can be single vented as well without any combustion air issues.

If you have hard water you'll need a softener. As others have mentioned, tankless do require annual flushing. We do it as a service to our customers, but all you need is a bucket, small water pump, hoses, and a gallon of vinegar. Just make sure when you install your heater, you put the isolation valves on.

Gas heaters are offer quicker recovery times and should cost less to operate than their electric counterpart. Of course, YMMV based on what kind you purchase. I'm not all the familiar with the new hybrid heat pump heaters. My area of the world has low energy costs and the high initial cost of the hybrid heaters tends to turn most people off.

bbqguru
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Re: Replace gas water heater with electric?

Post by bbqguru » Thu Mar 02, 2017 8:21 pm

ralph124cf wrote:I have been told by a local handyman (experienced, but not a licensed plumber) that natural vent water heaters may no longer be sold. Does anybody have actual knowledge about this? Perhaps it varies by locality, the plumbers union in this area has a lot of influence.

Ralph
Ralph, we sell around 3-4 truckloads of traditional standing pilot gas water heaters a year. I have heard nothing related to pilot heaters going the way of the dinosaur. There are plenty of places that would be unable to have any other type of gas heater (think older homes where no power is nearby)and the gas industries would push back hard. I do know they are increasing the efficiency of both gas and electric heaters, but they are doing that by changing the amount and type of insulation used on tank models.

If I had to guess, that may be more of a local or state issue.

meebers
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Re: Replace gas water heater with electric?

Post by meebers » Thu Mar 02, 2017 9:30 pm

I live in a "warm" climate, 2400Sq ft house, 3 bath. I have 55 gal NG WH and a NG fireplace. With the exception of a month or so in the winter, my gas bill is about $30. Of that $30, $15 is for fee's/taxes etc. I do not have a chimney per se, but a 4" metal vent thru the roof. It is non powered and sits in my garage. The original one failed after 10 yrs and was switched out for $800. We have bad weather from time to time and will always have hot water, and a fireplace to keep us warm. LP grill on the porch and a standby generator. Based on electric WH's I have had in other houses, it was way over $30/month. IMHO :happy
Last edited by meebers on Thu Mar 02, 2017 9:32 pm, edited 1 time in total.

gd
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Re: Replace gas water heater with electric?

Post by gd » Thu Mar 02, 2017 9:31 pm

OPer here. Nothing like a good plumbing problem... :D Think I addressed most points, but to clarify or reiterate:

1. Electric service is issue, but one of the more easily estimated and solved.
2. Want to relocate heater away from chimney because flue (shared with furnace) is poorly positioned and would need rework, need to repair old water main and in process would like to clean up bizarre plumbing that is literally twice as long as needed, rearrange space usage in basement. Moving water heater solves all three, and gives shorter hot water run.
3. I have electric sewage pump. Don't put any water down drain during power outages except minimal toilet flushes, so don't need hot water during electric outages. Had 4-day outage once and forgot we even had hot water.
4. Running non-chimney plastic venting has difficult placement problems due to house design. Gave up on HE furnace for this reason.
5. Initial costs are not an overriding concern simply because every type has hard-to-solve problems. Best we can estimate, in the end they're all similar within the large variability. It's a one-time expense for an essential utility, affordable for a good solution.
6. I'm not worried about smaller differences in operating costs-- chimney vented vs. direct vent vs. power vent vs. hybrid vs. tankless are all close enough so the other factors are just as important. Conventional electric is different, looks like 3x the operating costs of the others and I never considered it. That's why the hybrid surprised me.
7. I'm working with a plumber, one of the few tradesmen around me who actually will work to resolve difficult problems in my quirky house. He and his coworker suggested the hybrid after long discussions of other choices, probably because it's the simplest, most predictable outcome. It seems like newer technology, and I'm trying to validate his points and identify hidden issues.

Anyone have any experience or insights regarding the hybrid electric heaters?

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Re: Replace gas water heater with electric?

Post by Valuethinker » Fri Mar 03, 2017 6:46 am

gd wrote:OPer here. Nothing like a good plumbing problem... :D Think I addressed most points, but to clarify or reiterate:

1. Electric service is issue, but one of the more easily estimated and solved.
2. Want to relocate heater away from chimney because flue (shared with furnace) is poorly positioned and would need rework, need to repair old water main and in process would like to clean up bizarre plumbing that is literally twice as long as needed, rearrange space usage in basement. Moving water heater solves all three, and gives shorter hot water run.
3. I have electric sewage pump. Don't put any water down drain during power outages except minimal toilet flushes, so don't need hot water during electric outages. Had 4-day outage once and forgot we even had hot water.
4. Running non-chimney plastic venting has difficult placement problems due to house design. Gave up on HE furnace for this reason.
5. Initial costs are not an overriding concern simply because every type has hard-to-solve problems. Best we can estimate, in the end they're all similar within the large variability. It's a one-time expense for an essential utility, affordable for a good solution.
6. I'm not worried about smaller differences in operating costs-- chimney vented vs. direct vent vs. power vent vs. hybrid vs. tankless are all close enough so the other factors are just as important. Conventional electric is different, looks like 3x the operating costs of the others and I never considered it. That's why the hybrid surprised me.
7. I'm working with a plumber, one of the few tradesmen around me who actually will work to resolve difficult problems in my quirky house. He and his coworker suggested the hybrid after long discussions of other choices, probably because it's the simplest, most predictable outcome. It seems like newer technology, and I'm trying to validate his points and identify hidden issues.

Anyone have any experience or insights regarding the hybrid electric heaters?
OK a Heat Pump water heater will use between 1/2 and 1/3rd of what an electric bar one will use. Coefficient of Performance of 2-3.0 (kwhr of heat produced/ kwhr of electricity used).

If it's a hybrid HP, probably 1/2. So more expensive on a pa basis. Because you live in New England, your gas is also relatively expensive (pipeline capacity a major issue in winter).

I can't tell you about noise-- if that's a significant issue you need to talk to people who have them. But a good HP will still probably burn more money than a NG one given the different energy costs of gas and electricity. However if in the process you significantly rationalize other plumbing issues, that's probably a price worth paying. Just make sure it's an Energy Star product. Insulating your hot water tank will help, too.

Most utilities have a time of day tariff? So if you can set your HW not to come on during peak periods (well insulated tank, again) then that might generate significant savings?

I would not, generally, go the tankless route (for a house).

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Re: Replace gas water heater with electric?

Post by IowaFarmBoy » Fri Mar 03, 2017 7:56 am

I have a question about the heat pump style electric water heaters that perhaps someone can answer. As I understand, they harvest the heat from within the house and my question is where does this heat come from? In winter, this heat needs to be replaced by the heating system (unless it is in an unheated basement) so you are generating heat via your house heating system and then converting it to hot water via a heat pump. This doesn't seem particularly efficient. In the summer, if you are cooling your house, you would receive some degree of gain since the water heater is removing heat from the air.

Any thoughts about how this works out in the real world?

mouses
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Re: Replace gas water heater with electric?

Post by mouses » Fri Mar 03, 2017 8:19 am

You're a hardy soul if you don't care whether you have hot water or not for days. For myself, I prefer gas appliances because they work in power outages.

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Re: Replace gas water heater with electric?

Post by user5027 » Fri Mar 03, 2017 8:46 am

One thought to consider are power outages. With our traditional electric water heater I can get four days of showers before the tank gets too cold. These are not leisurely stand in the flowing water showers. They are "navy" showers; quick rinse - water off- soap up - and a quick rinse.

Good luck with a tankless.

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Re: Replace gas water heater with electric?

Post by Tom1320 » Fri Mar 03, 2017 9:03 am

This is a " I have a buddy that...." anecdote so take it with a grain of salt.

I have a buddy that went with a hybrid. Paid around 1500 for the tank. A few years (5 or 6) later the electronic controller stopped working. Would have been 500 for the parts. Since he did not notice much if any electric savings over the old resistance heater, he just put in a new resistance heater tank for the same 500.

Technology is great.....when it works. Sometimes simpler really is better.
"And this, too, shall pass away." How much it expresses! How chastening in the hour of pride! How consoling in the depths of affliction! - Our 16th President

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Re: Replace gas water heater with electric?

Post by hand » Fri Mar 03, 2017 9:20 am

dm200 wrote:2. The recovery rate of a gas water heater (same size tank) is much quicker than electric
This is a big deal for some use cases... Two people in a house with regular usage patterns, probably not a deal breaker. Frequently have numerous house guests who all want morning showers? You'll likely notice the difference.

If you're analytically minded, water heaters are typically specified in terms of capacity as well as recovery rate. Modelling your need for hot water will allow you to use the water heater specifications to determine whether a given water heater, irrespective of power source, will meet your needs.

For my specific use case, I found a smaller, but high recovery (gas) water heater best met my needs. If I had gone lower recovery electric, I would have required a much larger water heater.


P.S. Installing lower flow shower heads can have a major impact on your water heater requirements.

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just frank
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Re: Replace gas water heater with electric?

Post by just frank » Fri Mar 03, 2017 9:22 am

I have had a 80 gallon HP water heater in my attached garage for 4 years, and love it.

These units are now onto their second generation, and have gotten even better efficiency numbers. You should look for the EF numbers, higher is better. A regular electric tank is about ~0.90 (10 % of electrical energy is lost to the space), while current HPWHs get up to 3 or even 3.5 for an EF, meaning they will use 1/4 to 1/3rd of a normal electric tank. In most houses that running cost will be almost negligible, maybe $10-20/mo, so whether it is more or less than gas is not a big deal.

Some of the heat in the water comes from grid, the rest gets sucked out of the space (1/EF comes from the grid, 1-(1/EF) comes from the space). In the worst case, this is made up 100% by your gas heating system, in the heating season. But your gas heat BTUs are still a lot cheaper than electric BTUs, so the added cost is small. In fact, most gas HWHs are rather inefficient (due to the open chimney 24/7 and standing pilot)...you will pull a little more gas in the winter, but not such that you will notice.

In practice, the heat stealing is seldom an issue or as bad as the worst case. For one, in a cold basement, the heat from upstairs is flowing into the ground. If you 'steal' some of the heat before is flows into the earth, you reduce the temp in the basement slightly and the flux into the earth falls slightly. And then you are pumping the heat (in water) back upstairs, reducing the load upstairs slightly. In other words, most of the heat you are stealing is on its way to escaping your house already, so your HVAC will not try to make it up 100%, typical numbers are closer to 50%.

In the summer, of course, it is cooling and dehumidifying your basement. This will reduce your summer AC bill slightly, and if you run a power-sucking dehumidifier all summer in your basement, the HPWH will make it run a lot less, saving you there.

Summary: the heat stealing and summer savings basically cancel each other out, and both are small numbers cost-wise.

The issue is (1) the space around it will get slightly colder...maybe 1-2°F depending on basement size and (2) it can be noisy...mine sounds like my grandma's 1950s Frigidaire when it ran....whoosh/hum. Fine not in a living space. I removed a filter/grill from mine and it got a LOT quieter. and (3) you will need to drain the condensate soemwhere (in the summer, when it is a dehumidifier). Oh yeah,and mine is 7' tall.

Its a lot cheaper to run a new wire than to run a new vent, IMO, assuming you have 2 free slots in your breaker box.

IF you have a large usage, get a bigger tank. They do have slower recovery, so you want to have as much storage as possible. If you are super high demand (like 4 head shower stalls or Jacuzzi tubs every day) they it might not be right for you. I have a family of 4 and frequent house guests, with 2 gpm heads, and have never had a problem with the 80 gallon HPWH (except in hour 3 of my teens forever shower).

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Re: Replace gas water heater with electric?

Post by gd » Sat Mar 04, 2017 7:52 am

mouses wrote:You're a hardy soul if you don't care whether you have hot water or not for days. For myself, I prefer gas appliances because they work in power outages.
Oh, we cared. But with the town-mandatory sewage pump, we had approx 40 gal of sewage capacity for an unknown period, and saved it for toilet flushes. We didn't use the hot water because we couldn't let it run down the drain, particularly for 30 sec. while it warmed up. Made more sense to heat bowls of water on the gas stove. I will try never to replace our aging stove because new ones are specifically designed to not run without electricity, our old one can be lit with a match and stay on.

BTW, during the 4-day outage (some towns out 2 weeks) caused by an ice storm, there wasn't a generator for sale within 50 miles at least. Thousands rushed out to buy whole-house generators afterwards. After the utility companies then decimated the local road trees cutting branches back, we've had one 1-hour outage in the subsequent 5-8 years. But hot water won't be a problem in the next multi-day outage, my neighbor's new generator is so noisy we'll have to find alternate housing to get any sleep.

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Re: Replace gas water heater with electric?

Post by gd » Sat Mar 04, 2017 8:07 am

IowaFarmBoy wrote:I have a question about the heat pump style electric water heaters that perhaps someone can answer. As I understand, they harvest the heat from within the house and my question is where does this heat come from? In winter, this heat needs to be replaced by the heating system (unless it is in an unheated basement) so you are generating heat via your house heating system and then converting it to hot water via a heat pump. This doesn't seem particularly efficient. In the summer, if you are cooling your house, you would receive some degree of gain since the water heater is removing heat from the air.

Any thoughts about how this works out in the real world?
They're basically a reverse refrigerator. Most specify that if the ambient is < 50F, the heat pump won't do much, that's partly what the "hybrid" is for- backup. Your refrigerator has the same problem-- you pump heat out of the box to the kitchen, and a hotter kitchen is a harder-working refrigerator. A clever truly efficient house would have various heaters and coolers plumbed to utilize outside temperatures-- water heaters in summer, refrigerators in winter. Or maybe something *really* clever, like a root cellar or storing the milk in the creek out back...

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just frank
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Re: Replace gas water heater with electric?

Post by just frank » Sat Mar 04, 2017 9:25 am

gd wrote:
IowaFarmBoy wrote:I have a question about the heat pump style electric water heaters that perhaps someone can answer. As I understand, they harvest the heat from within the house and my question is where does this heat come from? In winter, this heat needs to be replaced by the heating system (unless it is in an unheated basement) so you are generating heat via your house heating system and then converting it to hot water via a heat pump. This doesn't seem particularly efficient. In the summer, if you are cooling your house, you would receive some degree of gain since the water heater is removing heat from the air.

Any thoughts about how this works out in the real world?
They're basically a reverse refrigerator. Most specify that if the ambient is < 50F, the heat pump won't do much, that's partly what the "hybrid" is for- backup. Your refrigerator has the same problem-- you pump heat out of the box to the kitchen, and a hotter kitchen is a harder-working refrigerator. A clever truly efficient house would have various heaters and coolers plumbed to utilize outside temperatures-- water heaters in summer, refrigerators in winter. Or maybe something *really* clever, like a root cellar or storing the milk in the creek out back...
Actually my HPWH works aok down to ~45°F air temp (which my garage seldom gets down to). And then it switches to the coil just to avoid frost buildup on the coils, as it does not have a defrost mechanism/controller (such as space heating heat pumps do). It would still be cheaper by a long-shot to run the HP, but no-one wanted to engineer in the added defrost function that would seldom be needed in an 'indoor' unit.

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Re: Replace gas water heater with electric?

Post by ralph124cf » Sat Mar 04, 2017 8:01 pm

It's sounding to me as if everybody in south Florida should switch to HP water heaters, basically free water heating for the same energy cost as air-conditioning.

Ralph

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just frank
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Re: Replace gas water heater with electric?

Post by just frank » Sun Mar 05, 2017 6:42 am

ralph124cf wrote:It's sounding to me as if everybody in south Florida should switch to HP water heaters, basically free water heating for the same energy cost as air-conditioning.

Ralph
From a run cost perspective, yes. Just need to find a large space for one where noise is not an issue, and in most of florida there are no basements. Attached garage could do nicely.

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Re: Replace gas water heater with electric?

Post by jharkin » Sun Mar 05, 2017 7:06 am

bbqguru wrote:
ralph124cf wrote:I have been told by a local handyman (experienced, but not a licensed plumber) that natural vent water heaters may no longer be sold. Does anybody have actual knowledge about this? Perhaps it varies by locality, the plumbers union in this area has a lot of influence.

Ralph
Ralph, we sell around 3-4 truckloads of traditional standing pilot gas water heaters a year. I have heard nothing related to pilot heaters going the way of the dinosaur. There are plenty of places that would be unable to have any other type of gas heater (think older homes where no power is nearby)and the gas industries would push back hard. I do know they are increasing the efficiency of both gas and electric heaters, but they are doing that by changing the amount and type of insulation used on tank models.

If I had to guess, that may be more of a local or state issue.
What Ralph might have heard is that in many areas natural vent are no longer put into new construction due to higher energy efficiency standards in the code in some locales. As you noted they are DEFINATELY still sold for replacements in existing homes.

Just like I can still buy a brand new steam boiler to replace the old one and retain the use of the 100+ old heating radiators in my creaky old house.

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Re: Replace gas water heater with electric?

Post by Valuethinker » Sun Mar 05, 2017 8:55 am

jharkin wrote:
bbqguru wrote:
ralph124cf wrote:I have been told by a local handyman (experienced, but not a licensed plumber) that natural vent water heaters may no longer be sold. Does anybody have actual knowledge about this? Perhaps it varies by locality, the plumbers union in this area has a lot of influence.

Ralph
Ralph, we sell around 3-4 truckloads of traditional standing pilot gas water heaters a year. I have heard nothing related to pilot heaters going the way of the dinosaur. There are plenty of places that would be unable to have any other type of gas heater (think older homes where no power is nearby)and the gas industries would push back hard. I do know they are increasing the efficiency of both gas and electric heaters, but they are doing that by changing the amount and type of insulation used on tank models.

If I had to guess, that may be more of a local or state issue.
What Ralph might have heard is that in many areas natural vent are no longer put into new construction due to higher energy efficiency standards in the code in some locales. As you noted they are DEFINATELY still sold for replacements in existing homes.

Just like I can still buy a brand new steam boiler to replace the old one and retain the use of the 100+ old heating radiators in my creaky old house.
There is nothing like the sound of an old steam or hot water heating system cranking into life, the popping of pipes ;-). Just hearing it makes me feel warmer ;-).

It's like the house is alive, but not in the scary horror film way, but in a reassuring way.

There's a Studio Ghibli animated film, based on a novel (Diana Wyn Jones?) "Lord Howl's Moving Castle" and the (moving) house has its own fire daemon that keeps it warm and powered up (Caratacus?).

It always sounds like the house daemon is getting going, muttering to itself, once I press the summoning dial. ;-).

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just frank
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Re: Replace gas water heater with electric?

Post by just frank » Sun Mar 05, 2017 8:58 am

Agree with @jharkin.

The issue with natural vent gas WHs is that there is a flue up the middle, where the hot gas combustion gases pass to heat the water. In a naturally vented unit that is open to the space when the unit is not firing...so you can insulate the outside as much as you want...but the heat is leaking into the flue and up the (open) chimney 24/7.

Talk about stealing heat from your space...that open chimney is still doing that even if the WH is cold.

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jharkin
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Re: Replace gas water heater with electric?

Post by jharkin » Sun Mar 05, 2017 9:17 am

^^^ Yep, and my natural vent gas boiler (~ 83% eff) does the same thing.

I could rip out the entire heating system and replace it with something power vent and get to 98% efficiency, but as a Boglehead spending $10,000 to save $200 a year in fuel costs just doesn't make a lot of sense.... :sharebeer

Valuethinker
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Re: Replace gas water heater with electric?

Post by Valuethinker » Mon Mar 06, 2017 6:14 am

gd wrote:I'm trying to replace a conventional chimney vent natural gas water heater. For various reasons, I want to switch to just about anything else to get away from the chimney. But plastic venting is difficult to place in my house, and although I had first not even considered electric due to its reputation of being more expensive than gas I was surprised to discover that electric hybrids appear as economical to operate as direct or power vent gas, with utility rates of $1.40/therm and $.197/kWh. It'll be in a basement with temps of 53 to 65F. High efficiency tankless gas is even cheaper, but even more difficult to install due to placement of 2 vent pipes. I'm not worrying about purchase and installation costs at this point, there are other practical issues, particularly installation, that are more important.

Can those knowledgeable about water heaters confirm that electric hybrids are operationally competitive with gas tanks in real life? Can anyone give me a sense of how noisy they are in heat pump mode (this is in unfinished basement below living area), and any other negatives of switching from gas to electric? Our usage is light and well distributed, and power outages prevent much water usage due to sewage pump so not a big factor.

HIgh efficiency tankless might be a remote possibility if my plumber gets creative, but I wonder about the warmup time. One of my goals is to get the heater closer to the faucet, to speed up hot water availability (without circulation loop, TIA :D ). In practice, how long from water flow to actual hot water out of the heater box? I read 15-20 secs, but have seen claims of longer.
In your shoes I would seriously consider HP hybrid simply for the installation issues. You might need a bigger hot water tank though, because recovery will probably be slower than with a gas fired one.

My guess is your bills won't work out to be radically different. Hot water is not a huge component of household utility bills* unless you heat with straight electric bar, and/or you have a large household (teenagers, as someone observed here, are not Energy Star approved ;-)).

I would not go tankless-- there's too much to go wrong in that.

Otherwise a straight high efficiency with a plastic vent pipe. But you want to avoid that.

* we do these things in kwhr but household of 2 in Victorian house in London, uses about 3000 kwhr pa of gas for hot water heating (heating is 8-10x that much). At our gas price thats about £180= USD 300 say pa. Our electricity is c. USD 22 cents/ kwhr. We have a high efficiency boiler (92%) which supplies both hot water (55 US gal tank = 310l) and heats the rads.

Even with teenagers I'd be amazed if our neighbours use twice as much gas for hot water. Unless someone in the household is given to taking a bath daily.

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runner9
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Re: Replace gas water heater with electric?

Post by runner9 » Mon Mar 06, 2017 7:42 am

We went to a power vent gas hot water tank and had previously changed to a HE furnace. With both venting out the side I removed the chimney and added some needed cabinets in the kitchen where it was. Running the hot water tank vent was a bit challenging, we just barely kept it 4 feet from a window. There's really no way to get the pipe outside? Just curious why not. Tons of windows and doors?

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gd
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Re: Replace gas water heater with electric?

Post by gd » Mon Mar 06, 2017 9:27 am

OP here. Plastic vents are hard to place because of odd stonework extending from chimney on closest wall, porch, windows within the 4' spacing, deck, and large old forced-air heating vents in basement that would result in some options placing basement-crossing vent pipes too low for free movement in the small basement. Honorable mention to low basement ceiling & ducting preventing tall heater installations, no floor drain & groundwater seepage so strong desire for raised tank with robust drip pan, deep winter snow needing high outside vent terminations, and a historic district that doesn't want to see big plastic candy-canes from the road. Houses with quirky charm come at a price.

My plumber suggested a placement tucked into a spot I hadn't considered, and after lots of thought and measurement I think I've got a possible vent routing worked out where everything just works when done one specific way. If the plumber agrees will probably go with a single-pipe power vent gas heater. If the venting works it's basically a coin flip within the unpredictability. I'm tending towards a less-complex device, and assuming (not confirmed) that a power vent will be quieter than a heat pump.

Interesting that a significant number of my internet searches on this (and lots of other topics) put bogleheads forum high on the list of responses. Thanks for all the responses, opinions and advice.

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David Jay
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Re: Replace gas water heater with electric?

Post by David Jay » Mon Mar 06, 2017 9:49 am

gd wrote:I was surprised to discover that electric hybrids appear as economical to operate as direct or power vent gas, with utility rates of $1.40/therm and $.197/kWh.
I find it hard to believe that electric can be as economical as gas. There are 3412 BTU per KW, so your cost for electricity is $5.77 per therm (defined as 100,000 BTU) versus $1.40 for gas.

If your electric system was 100% efficient, your gas water heater would have to be less than 25% efficient. It is not reasonable in this day-and-age that a bradn new gas water heater would only be 25% efficient.
Prediction is very difficult, especially about the future - Niels Bohr | To get the "risk premium", you really do have to take the risk - nisiprius

Valuethinker
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Re: Replace gas water heater with electric?

Post by Valuethinker » Mon Mar 06, 2017 10:47 am

David Jay wrote:
gd wrote:I was surprised to discover that electric hybrids appear as economical to operate as direct or power vent gas, with utility rates of $1.40/therm and $.197/kWh.
I find it hard to believe that electric can be as economical as gas. There are 3412 BTU per KW, so your cost for electricity is $5.77 per therm (defined as 100,000 BTU) versus $1.40 for gas.

If your electric system was 100% efficient, your gas water heater would have to be less than 25% efficient. It is not reasonable in this day-and-age that a bradn new gas water heater would only be 25% efficient.
Heat Pump. Essentially an air conditioner running in reverse.

Coefficient of Performance of a HP water heater is probably between 2 and 3-- spend 1kwhr electricity to move 2 to 3 kwhr of heat. If it is c. 3.5 (5.77/ 1.40) then you are at breakeven. Given a gas heater is never 100% efficient (say 90%) it's actually slightly closer than that (i.e. your actual useful gas cost is around 1.54-1.60/ therm).

There's another issue with the way most American HW heating is configured (indebted to Epsilon Delta for pointing that out). With a gas HW heater, the flue runs right out next to the tank and a lot of the heat generated goes straight up the spout. With a UK ("indirect") system that's not the case, there is a separate boiler which does both hot water and rad water via heat exchangers, so you don't have that heat loss. (I know I am explaining that badly, would have to dig around for a better explanation).

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Epsilon Delta
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Re: Replace gas water heater with electric?

Post by Epsilon Delta » Mon Mar 06, 2017 10:53 am

David Jay wrote:
gd wrote:I was surprised to discover that electric hybrids appear as economical to operate as direct or power vent gas, with utility rates of $1.40/therm and $.197/kWh.
I find it hard to believe that electric can be as economical as gas. There are 3412 BTU per KW, so your cost for electricity is $5.77 per therm (defined as 100,000 BTU) versus $1.40 for gas.

If your electric system was 100% efficient, your gas water heater would have to be less than 25% efficient. It is not reasonable in this day-and-age that a bradn new gas water heater would only be 25% efficient.
An electric hybrid is a heat pump with an efficiency of well over 100%. 300% is possible.

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David Jay
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Re: Replace gas water heater with electric?

Post by David Jay » Mon Mar 06, 2017 11:04 am

Epsilon Delta wrote:
David Jay wrote:
gd wrote:I was surprised to discover that electric hybrids appear as economical to operate as direct or power vent gas, with utility rates of $1.40/therm and $.197/kWh.
I find it hard to believe that electric can be as economical as gas. There are 3412 BTU per KW, so your cost for electricity is $5.77 per therm (defined as 100,000 BTU) versus $1.40 for gas.

If your electric system was 100% efficient, your gas water heater would have to be less than 25% efficient. It is not reasonable in this day-and-age that a bradn new gas water heater would only be 25% efficient.
An electric hybrid is a heat pump with an efficiency of well over 100%. 300% is possible.
"heat pump" is the key phrase. My mistake.
Prediction is very difficult, especially about the future - Niels Bohr | To get the "risk premium", you really do have to take the risk - nisiprius

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Re: Replace gas water heater with electric?

Post by neilpilot » Mon Mar 06, 2017 2:09 pm

Epsilon Delta wrote:
An electric hybrid is a heat pump with an efficiency of well over 100%. 300% is possible.
Excuse my ingnorance. I'm an engineer, understand most heat transfer concepts and units and the typical refrigeration cycle, and have even manufactured specialty CFCs.

However, I can't get my head around the term "efficiency" in the context of "300% is possible". What are you calling "efficiency"?

I Googled "heat pump efficientcy over 100%" but couldn't figure it out.

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Epsilon Delta
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Re: Replace gas water heater with electric?

Post by Epsilon Delta » Mon Mar 06, 2017 3:22 pm

neilpilot wrote:
Epsilon Delta wrote:
An electric hybrid is a heat pump with an efficiency of well over 100%. 300% is possible.
Excuse my ingnorance. I'm an engineer, understand most heat transfer concepts and units and the typical refrigeration cycle, and have even manufactured specialty CFCs.

However, I can't get my head around the term "efficiency" in the context of "300% is possible". What are you calling "efficiency"?

I Googled "heat pump efficientcy over 100%" but couldn't figure it out.
Efficiency in this case is measured as the amount of energy added to the water divided by the electric energy consumed by the heat pump.

The energy added to the water can be calculated as the temperature rise * mass of water * specific heat of the water.
The electric energy can be calculated as volts * amps or slightly more exotic formula if you consider the motor is a reactive load.

Energy is of course conserved. The majority of the energy added to the water actually comes from the environment, which is cooled by the heat pumps cold side.

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Re: Replace gas water heater with electric?

Post by ralph124cf » Mon Mar 06, 2017 4:18 pm

Epsilon Delta wrote:
neilpilot wrote:
Epsilon Delta wrote:
An electric hybrid is a heat pump with an efficiency of well over 100%. 300% is possible.
Excuse my ingnorance. I'm an engineer, understand most heat transfer concepts and units and the typical refrigeration cycle, and have even manufactured specialty CFCs.

However, I can't get my head around the term "efficiency" in the context of "300% is possible". What are you calling "efficiency"?

I Googled "heat pump efficientcy over 100%" but couldn't figure it out.
Efficiency in this case is measured as the amount of energy added to the water divided by the electric energy consumed by the heat pump.

The energy added to the water can be calculated as the temperature rise * mass of water * specific heat of the water.
The electric energy can be calculated as volts * amps or slightly more exotic formula if you consider the motor is a reactive load.

Energy is of course conserved. The majority of the energy added to the water actually comes from the environment, which is cooled by the heat pumps cold side.
It can even be considered higher than that, if the heat pump is in an air-conditioned space in a hot climate. In adding heat to the water the heat pump cools and dehumidifies the inside space, so free air-conditioning for the energy cost of hot water.

Ralph

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Re: Replace gas water heater with electric?

Post by Valuethinker » Tue Mar 07, 2017 8:47 am

neilpilot wrote:
Epsilon Delta wrote:
An electric hybrid is a heat pump with an efficiency of well over 100%. 300% is possible.
Excuse my ingnorance. I'm an engineer, understand most heat transfer concepts and units and the typical refrigeration cycle, and have even manufactured specialty CFCs.

However, I can't get my head around the term "efficiency" in the context of "300% is possible". What are you calling "efficiency"?
Epsilon Delta is the physicist/ engineer, I am just a hack who reads home renovation magazines, but layman's terms I think it is "Coefficient of Performance" i.e. ratio of kwhr of heat moved/ kwhr of electricity used to do so. A HP is just a reverse fridge, cooling the outside to warm the water inside. The actual conversion of electricity into electric motor drive should be pretty efficient (80%+?) and is included in that calculation.

Geothermal HPs can run 4 to 5, and I gather the best Japanese ASHP can run 4.0. Depending of course on the gap between internal and external temperature.

On the air conditioning side there's SEER (Seasonal Energy Efficiency Ratio) and I leave it to wikipedia to explain that better than I can.

In the south eastern US states, I believe ASHPs are quite common, because winter temperatures are high and it solves the summer AC problem in the same system, also not every subdivision has gas. They are also very common in Japan (again cold winters & hot summers).
I Googled "heat pump efficientcy over 100%" but couldn't figure it out.
https://energy.gov/energysaver/heat-pump-water-heaters
Heat pump water heaters use electricity to move heat from one place to another instead of generating heat directly. Therefore, they can be two to three times more energy efficient than conventional electric resistance water heaters. To move the heat, heat pumps work like a refrigerator in reverse.
https://cleantechnica.com/2016/11/30/he ... ey-energy/

has some good empirical data re COPs. 2.0 is certainly likely.

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