Bay Area Solar and Battery Calculator
Estimate the solar size, cost and savings for your home in about a minute. Built by Ally Electric & Solar, a licensed Bay Area installer since 2010 (CSLB #806465).
This is a rough estimate, not a quote. Your real design depends on your roof, panel layout, electrical panel and PG&E rate plan. We check all of that for free.
How this calculator works
We turn your bill into yearly usage using PG&E's March 2026 average residential price of about 39 cents per kWh, after taking out the roughly $24 monthly Base Services Charge that solar can't remove. Then we size the panels so they make the share of that usage you picked, using typical Bay Area production per kW and adjusting for your area, roof direction and shade.
Price uses Ally's typical range of $2.60 to $3.50 per watt for solar. A battery adds about $15,000 to $22,500 depending on brand and setup, based on our recent 2026 bids. Federal tax credits for homeowners who buy solar ended after 2025, so they are not included. A prepaid PPA or the SGIP battery rebate can lower the cost for some homes.
Typical results by area
| Area | Yearly production per kW (estimate) | Panels for 600 kWh a month |
|---|---|---|
| Berkeley, Oakland, Richmond, El Cerrito | about 1,450 kWh | 12 to 13 |
| San Francisco, coastal Marin | about 1,330 kWh | 13 to 14 |
| Walnut Creek, Concord, Tri-Valley | about 1,570 kWh | 11 to 12 |
| Los Altos, Los Gatos, San Jose | about 1,540 kWh | 11 to 12 |
South-facing roof, little shade, 440 W panels. Real numbers vary by roof tilt and microclimate.
Why add a battery in 2026?
Under California's current solar billing (net billing, often called NEM 3.0), PG&E pays very little for the solar power you send back to the grid, while power you buy in the evening costs the most. A battery stores your daytime solar and uses it from 4 to 9 pm, so far more of your solar replaces expensive evening power. It also keeps your fridge, lights and Wi-Fi on during outages and PG&E safety shutoffs. Read more about battery backup.
Questions people ask
How accurate is this estimate?
It is a starting point, usually within about 20% of the final design for a simple roof. Your real system depends on roof space, tilt, shading, your electrical panel and your rate plan. A free site visit gives you exact numbers.
Why does my bill matter more than my house size?
Solar is sized to the electricity you use, not the square footage. Two homes the same size can use very different amounts if one has an EV, a heat pump or a pool.
Do I need a new electrical panel for solar?
Sometimes. Older 100-amp or Federal Pacific and Zinsco panels often need an upgrade. We handle main panel upgrades ourselves because we hold both C-10 electrical and C-46 solar licenses.
Is the federal solar tax credit still available?
Not for homeowners who buy their system. The 30% credit for homeowners ended for systems installed after December 31, 2025. Some financing options, like a prepaid PPA, can still pass savings on to you.
Can I add a battery to the solar I already have?
Yes, in most cases. We add Tesla Powerwall 3, FranklinWH and Enphase batteries to existing systems, including older NEM 1 and NEM 2 systems.
Do you install outside the East Bay?
Yes. We work across the Bay Area, including San Francisco, Marin, the Peninsula and the South Bay.