Solar Installation, PG&E, 1 year true up

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anewboglehead
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Joined: Tue Mar 10, 2020 1:03 pm

Solar Installation, PG&E, 1 year true up

Post by anewboglehead »

mervinj made an excellent resource (viewtopic.php?t=291738) which I found very helpful when researching solar.

I am making a similar report with some additional information I learned after a year. Hopefully helps others as they consider solar.

System Summary:
Location: Bay Area, CA
Panels: 17 x 340W Hanwha Q Cells = 5.78kW
Inverter: Tesla 7.6 kW Inverter

Install Costs:
Quoted Cost: $12,014
Federal Tax Credit: $3,124
Other Cost Reducers (SREC, referral, CC rebate): $764
Out of Pocket Cost: $8,126
Estimated Energy Savings: $2,250 per year
Estimated Breakeven: 3.2 years

Production Data
Estimated by Installer: 9,431 kWh/year
Estimated by PVWatts: 9,468 kWh/year
https://pvwatts.nrel.gov/

2021 Annual Production (measured): 9,137 kWh*
2021 Electricity Consumption: 8,113 kWh
2021 Net Generation: 1,024 kWh

*Installation performed incorrectly, causing inverter to engage in frequent safety shutdowns, reducing solar output by 50% for two months. Additionally, monitoring app cut out multiple times during the year and is missing data. The missing data was estimated from users with similar characteristics (size, location, etc) on SolarEdge public. I estimate approximately 500 kWh of lost production.

Utility Charges
2021 PG&E NEM 2.0 Charges: $127 (Non-Bypassable Charges)
2021 SJCE Net Surplus Compensation: -57 (Anticipated, credit of 5.6c per kWh x 1,024 kWh)
2021 Net Out-of-Pocket Cost: $70
Estimated Electricity Savings: $2,607 (8,133 kWh x 33c/kWh = my average cost per kWh in pre-solar 2020, less 70)
Approximate breakeven: 3.1 years

A side note:
My gas usage decreased by ~$500. With the surplus "free" electricity, I shifted some of our heating costs from furnace (gas) to electric heat. I had also made some improvements to insulation, so unclear what portion of the gas reduction is due to shift to electricity and insulation. In prior years, our annual usage was consistently between 8,000 and 8,200 kWh per year. This is about in line with our use in 2021, I'm guessing it is because the increase in electricity use for heat was offset by less use of AC due to insulation improvements.

How Billing Works
After the true up, I have a better understanding of how PG&E NEM 2.0 works, with a CCA (SJCE).
Under NEM 2.0, both PG&E and SJCE have an NEM balance that is calculated each month and rolled over until the annual true up. You don't pay anything (except NBCs, covered below) until True Up.
The balance is calculated by summing usage * TOU rate on an hour by hour basis, and then adjusting for fees.
Example:
- In the summer between 3 and 4 PM, the rate for electricity is 40c/kWh, my system generates 4 kWh. During this period, I use 1 kWh. PG&E will report net generation of 3 kWh, and credit +$1.20 to my NEM balance.
- In the winter, between 9 and 10 AM, the rate for electricity is 20c/kWh, my system generates 1 kWh. During this period, I use 5 kWh. PG&E will report net usage of 4 kWh, and debit 80c from my NEM balance.
- One effect of this is that your solar production reported from your system will not match the amount generated from PG&E, because PG&E is reported Net Usage.

After summing the hourly amounts, there are also many charges that are applied monthly. One of the key charges is Non-Bypassable Charges (NBCs). This is the minimum you will pay to PG&E - some think of it as a connection fee. So even if your NEM balance is negative every single month, you still pay this fee. For me, it is about $10/month. If your NEM balance is positive, I believe this counts as a credit towards costs. So if your NEM balance was 150 owed at the end of the year, and you had paid 120 in NBCs, you would owe $30 (or at least this is my understanding from reading the bill, I have not personally experienced this situation).

There are a slew of other charges that I cannot make heads or tails of, but appear each month. The net result is that your NEM balance is less than your credits.

An example from my past year:
In two peak summer months, I generated approximately 400 kWh extra per month. my summer TOU rates vary between 25-50c/kWh. My NEM credit was about $80/month.
In two winter months, I used approximately 400 kWh extra per month. My winter TOU rates vary between 20-30c/kWh. My NEM debit was about $100/month.
So generating the same amount of kWh at a higher rate, and using them at a lower rate, resulted in an NEM balance owed due to the fees.

For a reference point, I generated 1k kWh surplus, all during the summer, and my NEM balance was around -70 for PG&E, and another -75 for SJCE. I suppose I had about $190 of wiggle room for PG&E, given that I could go up to an NEM balance of 120 without paying more out of pocket.

If the NEM balance at true up is negative, nothing is paid out.
If the NEM balance at true up is positive, you owe PG&E the balance (less NBCs)
The NEM balance is then reset to zero for the next year.

The "payout" for excess kWh is done via Net Surplus Compensation (NSC).
NSC only occurs if you are a net generator (you produce more than you consume). In the scenario where you used more kWh than you produced, but your NEM is negative., you would not be eligible for NSC.
NSC is small beans. PG&E NSC rate is around 3c/kWh, my CCA is about 6c/kWh. There are some CCAs that pay full retail!
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