Residential Solar Analysis
Prepared October 2026 · SIA Solar Design Studio
Still a good investment. But on EV2A your solar makes power at midday (cheap hours) while your costly hours are the 4–9pm peak and overnight — so the battery adds about $11,800 by moving your own solar into them. That's why it's in the pick.
A ~15% dealer fee is baked into financed prices, shown nowhere as a line item — roughly $3,600 straight off your return. Always ask for the standalone cash price. A credit union or HELOC beats a solar loan.
What we found
From your twelve PG&E bills. Rises to ~16,100/yr once the heat pump is in (page 2).
PG&E's EV time-of-use rate. Peak (4–9pm) up to 54¢; off-peak ~23–30¢ overnight.
The 30% credit (25D) ended Dec 31, 2025. Any quote still showing it is wrong.
NEM 3.0 — exports earn ~a quarter of retail. A self-used kWh is worth ~4–5× an exported one.
Two near-flat 7° faces, 86–90% sun after a slight trim. Room for 40+ panels — not roof-limited.
Electrifying HVAC (COP 2.8) adds winter load, much of it in the evening — right on the EV2A peak.
On EV2A, storing midday solar for the 4–9pm peak and overnight load adds ~$11,800 over 25 yrs.
What CA buyers pay. Shopping to the low end is worth ~$14,000 here (page 4) — it's the job we do.
Two cars charging off-peak, already in your bills. Solar can't reach them directly — a battery can.
We shop your system, so you land at the low end — worth ~$14,000 here
This analysis is free and independent. If you want to go ahead, so is the next part.
Three vetted, competing installers quote the same system, and we give you our own read on each — so you land near $2.50/W, not $3.97. On this system that gap is ~$14,000.
No phone number, no lead-selling, no wall of sales calls. One email starts it, one ends it. Your details never go to an installer unless you ask.
We help you vet installers and read every quote line by line — what's padded, what to push on, when to walk — through to the day it powers on.
Next steps
Divide a recent PG&E bill by the kWh used, and note your peak vs off-peak split.
We line up three vetted PG&E NEM-3.0 installers at a fair price, or do it yourself and compare per watt.
California's battery rebate (~$150–200/kWh) can take a real bite out of the Powerwall. We'll confirm fund availability.
Separately from any financed price. The gap is the dealer fee.
Your usage, in depth
Prepared October 2026 · SIA Solar Design Studio
How your bill becomes usage
We didn't guess your usage — we read it off your twelve PG&E bills. You're on EV2A, so each bill splits your power into three time-of-use buckets. Add a year of them up and your home used 12,775 kWh, at an electric bill of about $379 a month (~$4,551/yr). You're a heavy user — roughly 2× a typical California home — which is exactly why solar is worth doing here. Most of that power is off-peak and overnight (your two EVs charging), with evening peaks: the shape, not just the total, decides how solar and a battery pay.
What you use today, month by month
Your actual electricity use by month (kWh), from your bills. Summer is highest — air conditioning — and winter is lowest today, because your heat is currently gas.
Your usage is about to change — here's how we modeled it
You told us two things that change the picture, and we built both into every number in this report:
- Two EVs, charged overnight. Already in the bills above — they're most of your off-peak use, and they're why a battery matters (solar can't reach an overnight car directly).
- Electrifying your HVAC to a heat pump. Your gas bills show about 350 therms a year of space heating (heavy in Dec–Feb). Moving that to a heat pump at COP 2.8 — i.e., 350 therms × 29.3 kWh/therm × 90% ÷ 2.8 — adds about 3,296 kWh/yr of electricity, almost all of it in winter evenings.
That takes your home from 12,775 to ~16,071 kWh a year, and it shifts new load onto winter evenings — right into EV2A's expensive peak.
Monthly electricity use: today (gold) plus the heat-pump load we modeled (blue). The winter months jump the most — and winter is when your roof sees the least sun, which is why the system leans on a battery and the grid in those months.
Your roof
Prepared October 2026 · SIA Solar Design Studio
The recommended 24-panel (9.6 kW) layout on Google's annual sunlight map of your roof. Yellow is the most sun, purple the least — the dark bands are tree shade. Panels sit on the east and west faces where the roof stays warm, split 12 and 12.
The system we recommend
| Solar | 24 × 400 W = 9.6 kW DC |
| Storage | 1 × Tesla Powerwall 3 (13.5 kWh) |
| Estimated year-1 production | ~13,000 kWh AC (NLR PVWatts v8) |
| Roof faces used | East (~83°) and West (~262°), ~7° pitch |
| Split | 12 panels east (morning sun), 12 west (afternoon sun) |
Why 9.6 kW and not less: your future load is ~16,100 kWh/yr, and a battery lets you actually use a larger array instead of exporting it at 7¢. Nine-point-six kW is the point where added panels stop paying under NEM 3.0 (page 5). Why one Powerwall: 13.5 kWh is enough to shift a day's midday surplus into your evening peak and overnight load; a bigger pack would sit half-empty and lose money.
Production by month
Expected AC output after measured shading (kWh). December runs about a quarter of summer — the trees shade the roof hardest in winter, which is also when the heat pump needs the most power, so winter leans on the grid and the battery. Production from NLR PVWatts v8.
Shading & your roof's resource
Prepared October 2026 · SIA Solar Design Studio
How much a roof is worth for solar comes down to its Total Solar Resource Fraction (TSRF) — the share of the best possible output each face captures. It multiplies two things, both from Google's 3-D scan:
- Solar access — sunlight reaching the face after the trees. Yours runs 86–90%: good, with a real haircut from the canopy.
- Orientation factor — what a face at that tilt and direction collects versus the best orientation here (~1,630 kWh/kW/yr unshaded). East–west at 7° sits a little below a south-facing ideal, but not by much when the roof is nearly flat.
| Roof face | Area | Orientation | Solar access | After shade |
|---|---|---|---|---|
| East (12 panels) | 73 m² | ~83°, 7° pitch | 89.8% | 1,378 kWh/kW |
| West (12 panels) | 70 m² | ~262°, 7° pitch | 86.1% | 1,330 kWh/kW |
Both faces clear the bar for a worthwhile install comfortably. The ~13–18% the trees cost is real, but it's priced into every figure here — we size to the sun you actually have.
An apartment complex from above (sample) — the canopy that drives the shade numbers.
Shade through the year
The sun your roof gets swings hard by season. Here's midday across five months — fully lit in summer, largely shaded by December. The production figures already carry that dip.
A day on your home
Prepared October 2026 · SIA Solar Design Studio
Here's a typical summer day with your future load (EVs + heat pump), hour by hour, under three setups. The black line is your home's demand. The shaded band is what powers it: your own solar (gold), your battery (blue), and the grid (red). The pink column is EV2A's 4–9pm peak — the hours power costs the most.
Read left to right. No solar: you buy everything from the grid, including the expensive 4–9pm peak. Solar only: midday is covered and some is exported for 7¢, but by the time the peak hits, the sun is fading — you're back on the grid at 54¢ exactly when it's dearest. Solar + battery: the midday surplus that would have been exported for 7¢ is stored and spent in the peak and overnight instead — the red grid band shrinks right where it costs the most. That shift is what the battery is worth on EV2A, and why it pays here when it wouldn't on a flat rate.
Typical summer day, averaged from the 8,760-hour model on your rate and load. Winter looks similar but with less midday solar and more evening heat-pump load, which the battery and grid cover.
The money
Prepared October 2026 · SIA Solar Design Studio
Your rate: EV2A
You're already on EV2A, PG&E's EV time-of-use rate. Your solar produces at midday — off-peak (cheap) — while your costly hours are the 4–9pm peak and overnight. That's the whole reason the battery earns its keep.
| Period | Summer (Jun–Sep) | Winter (Oct–May) |
|---|---|---|
| Peak — 4–9pm | 53.8¢/kWh | 48.6¢/kWh |
| Part-peak — 3–4pm, 9pm–12am | 42.8¢/kWh | 46.9¢/kWh |
| Off-peak — 12am–3pm | 22.6¢/kWh | 30.0¢/kWh |
| Exported solar (NEM 3.0) | ~7¢/kWh | ~7¢/kWh |
What you pay per watt — and why it matters most
Price per watt is the single biggest lever on your return, and it's the one you control. We modeled three, from what a well-shopped buyer gets to what many PG&E buyers actually pay. The system is identical in each — only the price changes:
| Installed price | What it is | Net cost | Payback | 25-yr savings |
|---|---|---|---|---|
| $2.50/W | Well-shopped — what we get you | $39,400 | 11.3 yr | $50,248 |
| $3.10/W | Typical California price | $45,160 | 12.8 yr | $44,488 |
| $3.97/W | High — what many PG&E buyers pay | $53,512 | 17.1 yr | $36,136 |
Cash purchase, at a well-shopped $2.50/W
| Solar, 9.6 kW at $2.50/W | $24,000 |
| Tesla Powerwall 3 (13.5 kWh), installed | $15,400 |
| Federal tax credit | −$0 |
| SGIP battery rebate | not included — ask (~$2,000–2,700) |
| Net cost | $39,400 |
| Year-1 savings | $3,181 |
| Net savings over 25 years | $50,248 |
Cumulative position, cash purchase of the recommended 9.6 kW + Powerwall 3. The line crosses zero at payback (~11.3 yrs); the small dip at year 16 is the battery replacement. SGIP, if available, pulls payback in further.
Does the battery pay? Here, yes.
| Net cost | Payback | 25-yr savings | |
|---|---|---|---|
| Solar only, 9.6 kW | $24,000 | 11.6 yr | $38,461 |
| Solar + 13.5 kWh Powerwall 3 — recommended | $39,400 | 11.3 yr | $50,248 |
On a flat rate a battery is just backup. On EV2A, with a 54¢ peak and heavy overnight and winter-evening load, storing midday solar and spending it in those hours is worth about $11,800 over 25 years here — and it doesn't lengthen your payback. One Powerwall (13.5 kWh) is the sweet spot; it also gives whole-home backup through Napa's wildfire-season shutoffs.
How big a system? (solar only)
| Panels | Size | Cash cost | Payback | 25-yr savings |
|---|---|---|---|---|
| 18 | 7.2 kW | $18,000 | 10.2 yr | $35,836 |
| 24 — recommended | 9.6 kW | $24,000 | 11.6 yr | $38,461 |
| 28 | 11.2 kW | $28,000 | 12.3 yr | $39,628 |
| 32 | 12.8 kW | $32,000 | 13.0 yr | $40,486 |
Under NEM 3.0 a smaller array earns a higher return (you self-use more of it) while a bigger one banks more total dollars with diminishing returns past the point it starts exporting at 7¢. Paired with the battery to soak the midday surplus, 9.6 kW is the balance for your load — bigger mainly adds export you're paid little for.
Paying for it
Pay cash if you can, or use a credit-union loan or HELOC. Avoid dealer-financed solar loans: they bury a ~15% dealer fee (about $3,600 here) in the price rather than showing it, which drags your return and adds 2–3 years to payback. Always ask for the standalone cash price.