The bill, before solar and after

Was it worth it?

Financially, no, not yet: in 21 of the 22 months from December 2024 to September 2026 I paid $19,617 in up-front cash, bills and loan payments.
At my pre-solar prices, held flat, the same 35,933 kWh would have cost $7,765: $0.234 per kWh June to September, $0.202 otherwise, every charge included.
In the latest 12 months my bills ran $237 a month under those prices, $12 more than my loan payment.
So at those prices held flat, the cash comes back in 2043, after my last loan payment in December 2039.
Of the $13,030 I paid up front, $10,712 bought the two Powerwalls. They carried the house through 16 grid failures, 93 minutes in all, which no bill prices.

At prices rising 2% a year instead, the cash comes back in March 2041.

Summer 2026 had 968 cooling degree days at my station: tied for the second highest of the 6 summers in the table below.

June to August at my weather station
Summer	Days recorded	Mean °F	Cooling degree days	Days ≥ 90°F	Days ≥ 100°F
2020	42 of 92	—	—	—	—
2021	92 of 92	74.9	921	15	0
2022	92 of 92	75.8	995	15	0
2023	84 of 92	74.3	865	6	0
2024	92 of 92	75.5	968	11	0
2025	91 of 92	74.7	913	16	2
2026	92 of 92	75.5	968	13	2

The tax credits and the Powerwall rebate paid part of the cost directly, so they add nothing to either side.
Left out of both sides: November 2024, January 2025, October 2026 and November 2026. After September 2026 the figures project the latest 12 complete months.

Year against year

The utility's charges reach back to Sep 2022, so whole years compare in dollars. Prices and use both change, so the difference is not all solar.
In the last full year before solar, Nov 2023 to Oct 2024, the bills came to $3,848.16, with no loan payment on record.
In the latest full year, Nov 2025 to Oct 2026, the bills came to $1,718.31 and the 12 loan payments to $2,694.84: $4,413.15 in all.
That is $564.99 more than the year before solar, or 115% of it.
The bills alone came to $1,718.31: $2,129.85 less, or 45% of the year before solar. That leaves out the solar project, so it is not the cost of going solar.
The two sides are not the same household. The EV arrived in Feb 2024, so the year before solar had it for 9 of its 12 months.
Every year after PTO had it all twelve months. So more of the load after solar is EV charging, and the comparison is not like for like.
The project's two Powerwall 3 batteries carried the house through 16 grid outages, all short. A bill does not measure that (see the outages page).

This control zooms the charts that have a date axis. Totals are for the full record.

before solar after solar straddles PTO solar loan payment no bill

Every bill and loan payment, Sep 2022 to Oct 2026

Each bar is one month: 26 bills before solar, 23 after, and one that straddles the PTO date of 8 November 2024.
Payments are not bills, so they are left out. A balance adjustment is not a bill either.
Each bill belongs to the calendar month that holds the middle of its cycle: the bill date less 15 days.
The Aug 2024 bill is 3 charges, from 21 August 2024 to 6 September 2024, drawn as one stacked bar that counts once.
The bill dated 21 November 2024 ($182.40) covers 25 October 2024 to 21 November 2024.
So part of it is before PTO and part after. It is drawn in outline and left out of every comparison below.
The gray part above a bar is the solar loan payment debited that month.
22 payments are on record, from 13 January 2025 to 14 October 2026. A payment belongs to the month it posted in.
After PTO, Nov 2024 and Dec 2024 have no loan payment on record, so they show a question mark: absent, not $0.

mean bill before solar mean bill after solar plus the loan payment one bill

The same month, before and after

Each group is one calendar month.
The first bar is the mean bill before PTO, and the second the mean bill after.
The third is the same months after PTO with that month's loan payment on top. So a small summer bill is not read as the whole cost.
Each dot is one bill, or one bill plus its loan payment. So a mean of two looks like what it is.
The figures under each group count the bills in each bar.
A bill after PTO whose month has no loan payment on record is left out of the third bar. It does not get a $0 loan.
A household uses electricity differently in each season.
So the comparison is month against month: July against July, not July against January.

Twelve months at a time

Each row is twelve calendar months from Nov to Oct, so the years after solar start at PTO. Its second line counts the months with the EV.
A row has a total only when every month in it has a bill. A row short of bills shows as incomplete, not summed short.
The first year after PTO, Nov 2024 to Oct 2025, holds the straddling bill and only 10 loan payments, so it is drawn in outline with no loan total.
A later year with a loan payment in every month shows the loan as a gray segment. Its label gives the bills, the loan, and both together.
The front page counts solar years, from the day the system was energized, and spreads each bill over its service days, so its sums differ.
By that count the bills came to $3,854 in the year before, $855 in year 1 and $1,699 in year 2, whose bills so far cover 346 of 365 days.
The solar loan is a separate line: 10 of 12 payments, not totaled in year 1; $2,695 in year 2.

Before solar: without the EV, and with it

The EV, in the bills before solar

My usage rose after my EV arrived in Feb 2024. The bills show it in dollars.
7 calendar months have a bill before solar in both 2023 and 2024: Mar, Apr, May, Jun, Jul, Sep, Oct.
In those months the bills with the EV came to $2,375.97.
The same months a year earlier, without it, came to $1,887.98.
That is $487.99 more, or 126% of the year before.
Aug 2024 is left out: its bill is several charges from the meter swap, and their billed days cannot be confirmed.
This is dollars, not usage. There are no kilowatt-hours for the months without the EV.
Rates also changed between the two years.
The EV arrived in this span. The bills alone do not show how much of the change it caused.

net import net export average temperature

What the meter saw on each bill

Each bar is the net kilowatt-hours on one bill: what the house drew from the grid less what it sent back.
Below the line, the house exported more than it imported.
This chart is the utility's usage history. It starts with the bill dated 24 July 2024, so it has 6 bills before solar.
The chart of cost per kWh uses other sources for kWh before PTO.
The largest bill after solar was $500.41, dated 23 January 2026.
That cycle had 1,901 kWh of net import and an average of 35°F.
The dashed line is each cycle's average temperature, from the same usage history.
The page does not model what drives winter use.
It shows the bill's kWh beside the bill's dollars, so you can read a high winter bill against both.

peak, Rate 195 off-peak super off-peak flat, Rate 180 all-in average before solar, computed no kWh billed, no price

The price of a grid kilowatt-hour

The lines are the price each bill prints for one more grid kilowatt-hour: delivery, power supply, the DER charge and the MFC, added together.
Until the cycle that starts 20 February 2025, the house was on Rate 195, time-of-use, with three prices. From then it is on Rate 180, one flat price.
A Rate 180 bill prices delivery in blocks. The line uses the block the bill's last kWh fell in, and the tooltip gives every block.
These are the utility's own rates, so export credits do not touch them. After PTO the bill nets exports, and bill over kWh is no longer a price.
14 of the 32 bills bill no kWh, so they print no price. Those cycles are hatched; no rate is filled in from elsewhere.
The amber line is the whole bill, Basic Service and adjustments included, over the kWh delivered, for the 18 cycles before PTO from 22 April 2023 to 20 October 2024.
Over the 8 cycles where the two overlap, it sits below the peak rate, above the off-peak rate in 1 of 8 cycles and above the super off-peak rate.
Fixed charges are not in the lines: Basic Service at $0.51 to $0.56 a day, and from 20 November 2025 the CBC, $0.033 to $0.0372 per kW a day.

Caveats

What these figures do not show

Dollars mix price and use. Rates changed between Sep 2022 and Oct 2026, so a change in a bill is price, use or both. These figures do not separate them.
The rate plan also changed after PTO. The daily meter record shows the flat plan from 13 March 2025, marked on the first chart.
The bills date it to the cycle that starts 20 February 2025: that cycle holds 13 March 2025, and a bill prices its whole cycle at one rate.
Winters differ. Household use varies from one winter to the next, and each calendar month has only 1 to 3 bills on a side.
Before solar there are dollars, and fewer kilowatt-hours. The charge history reaches back to Sep 2022.
Kilowatt-hours before PTO come from the bills, the daily meter file and an older usage sheet, with gaps. The chart of cost per kWh uses them from Nov 2023.
The loan line is bank debits, and nothing else: the solar loan payments from a checking account, as the bank lists them, from 13 January 2025.
The loan's amount, rate and term are not in this record, so these charts compute no schedule and no balance.
Up-front costs, incentives and tax credits are not in these charts. Loan payments are cash out, not the energy cost of a kilowatt-hour.