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Divide your yearly electricity use by how much one kilowatt of solar produces where you live, then divide by the size of a panel. A home using 14,000 kWh a year in a place where each kilowatt makes about 1,500 kWh needs roughly 9.3 kW, which is about 22 panels at 420 watts each. The calculator on this page does that arithmetic using real sunlight data for your address.

Yes, reasonably well. Your bill divided by your utility's rate gives your kilowatt-hours, and that is what determines system size. It is less precise than reading the kWh figure off the bill, because rate plans vary and part of every bill is fixed charges rather than energy, so this calculator subtracts an assumed fixed charge before converting. If you know your kWh, enter that instead.

Good enough to tell you whether solar is worth a conversation, and not good enough to sign. Production comes from NREL's PVWatts model, which is well validated, but it is being asked about an assumed roof: a south-facing plane at a typical pitch with no shading. Your actual roof has an orientation, a pitch, obstructions and probably a tree. Price is a market-based range, not a quote. Expect the real figures to land inside the range shown, and expect a site visit to move them.

Not for a homeowner buying a system outright. The Section 25D residential credit was ended by the One Big Beautiful Bill Act for expenditures after 31 December 2025, with no phase-down. The Section 48E commercial credit runs through 2027 and can be claimed by the owner of a third-party-owned system, so a lease or power purchase agreement can still pass some of that benefit through as a lower rate. State and utility incentives are unaffected and vary widely.

Take what the system costs after incentives and divide by what it saves each year, accounting for two things that pull in opposite directions: panels lose about half a percent of output annually, and utility rates tend to rise. What a saved kilowatt-hour is worth also depends on your utility. Under full retail net metering every kilowatt-hour you produce offsets one you would have bought. Under net billing, exported power is credited below retail, so only the power you use as you make it saves the full amount, and a battery starts to matter.

Not to save money, in most places. A battery earns its keep in two situations: your utility credits exported power below the retail rate, so storing your own production is worth more than selling it, or you want the lights to stay on during an outage. If neither applies, solar alone has the better return, and a battery can be added later.

Close, but never exactly zero, and how close depends entirely on your utility. Every utility bills a fixed monthly charge for the connection itself — a Power Access Charge at LADWP, a daily basic charge at SCE — and that is owed whatever your array produces. On a utility that nets your exports against your imports at close to the retail rate, a well-sized system takes the energy line to almost nothing and leaves roughly that fixed charge. On California's NEM 3.0 tariff, exported power earns far less than the power you buy back in the evening, so a solar-only system leaves more than that. Storage is what closes the gap.

NEM 3.0, or the Solar Billing Plan, is the California Public Utilities Commission tariff that replaced retail net metering for the three investor-owned utilities: PG&E, SCE and SDG&E. Under it, power you export is credited at an avoided-cost value that is a fraction of what you pay to import. It does NOT automatically apply to municipal utilities, which set their own rules — LADWP, for example, is customer-owned, sits outside CPUC jurisdiction and still credits exports at close to retail. Which utility serves your address therefore changes the economics substantially, and the calculator on this page identifies it and prices accordingly.

It depends on your tariff and on what you want it for. Financially, a battery earns its keep where exports are paid far below retail: it stores your midday surplus and discharges it in the expensive evening hours instead of selling it cheaply. Under retail netting the grid already does that for you at no cost, so a battery there is a backup-power purchase rather than a savings one. Separately from the arithmetic, a battery is what keeps your lights on in an outage — solar alone shuts down when the grid goes down, for the safety of line workers.

Because it is sized for the next twenty-five years rather than the last twelve months. Panels lose roughly half a per cent of their output every year, so an array matched exactly to today's usage would be covering closer to 88% of that same usage by year 25. Households also tend to add load over time — a car, a heat pump, air conditioning. The extra capacity is far cheaper fitted once than added later, when it means a second permit, a second inspection and often an inverter with no headroom left to take it.

A grid-tied solar system without storage shuts down automatically when the grid goes out. That is a safety requirement, not a fault: it stops your array energising lines that utility crews may be working on. To keep power during an outage you need a battery and the right switching hardware, which isolates your home from the grid and runs it from stored energy and daylight.

If the covering is near the end of its life, yes — it is far cheaper to re-roof before the array goes on than to remove and refit panels a few years later. A rough rule is that if the roof has less than about ten years left in it, deal with it first. This is one of the things a site visit settles; it cannot be judged from an aerial photograph or from anything on this page.

Yes, at reduced output. Panels respond to light rather than heat and in fact run slightly more efficiently when cool; what falls in winter is the number of daylight hours and the angle of the sun. A cloudy day typically produces some but not all of a clear day's output. Annual figures already account for this — the production model uses decades of measured satellite irradiance for your specific location, month by month, not a sunny-day best case.

Very little mechanically, because there are no moving parts. Output drifts down slowly as panels age, and dust or leaf litter reduces production until rain or a rinse removes it. The component most likely to need attention over the life of a system is the inverter, which is electronic. What matters more than maintenance is monitoring: a fault that halves your output is invisible unless something is watching the numbers.

That depends on how the system was paid for, and it is worth deciding before you sign anything. A system owned outright transfers with the property. A financed system has a loan balance that must be settled or assumed, and a leased system or power purchase agreement has a contract the buyer has to be willing to take on. Ask us to walk through the differences for your situation rather than taking a general answer from a web page.

The installation itself is usually short. What governs the overall timeline is permitting and utility interconnection approval, which vary by jurisdiction — the City of Los Angeles, the County, and each incorporated city all run their own process. We will give you a realistic schedule for your address rather than a number chosen to sound good.