Solar Battery vs Generator for Backup in California

Match the tool to the outage you actually face:

• Hours to a few days, essentials only — a battery. One 13.5 kWh unit runs a fridge, lights, Wi-Fi, a furnace fan, a medical device and a small pump (about 7.2 kWh a day) for about 1.7 days with no sun, and solar refills it on every sunny day if the system is designed to run when the grid is down. That recharge costs nothing while the grid is out.
• Several days with central air or other heavy loads — a standby generator. A 24 kW unit on natural gas runs a 10.5 kW load, central air included, for as long as gas flows, at roughly $3.85 an hour. One battery lasts about an hour at that load.
• Lowest upfront cost — a portable generator, if you accept refueling, extension cords and strict carbon-monoxide precautions.

Many homes combine them: a battery for the frequent short outages and a generator for the rare long one. Whether the two can be connected depends on the battery system — see below.

Comparisons often give each option its own flattering scenario. Here every column gets the same house and the same two loads: (A) critical loads of 7.2 kWh a day through a three-day shutoff — the profile our multi-day PSPS battery model uses — and (B) a hot afternoon with central air pushing the house to about 10.5 kW. Three days is a planning case, not a worst case: SCE ran 13 PSPS events in 2025, and in ten of them more than a day passed between the first and the last circuits coming back (SCE post-season report).

Method. Battery: 13.5 kWh less a 10% reserve (12.15 kWh) divided by the load; an average California home used 503 kWh a month in 2024, about 16.5 kWh a day (EIA). Portable: Honda’s 1.2-gallon tank runs 8.6 hours at quarter load (650 W) and 3.3 hours at its rated 2,600 W; a lighter load burns no more fuel per hour than the quarter-load rate. Gasoline is $6.003 a gallon, EIA’s California average for the week of September 21, 2026. Standby: Generac lists 203 ft³ of natural gas an hour at half load and 306 at full load, converted at its own 1,000 BTU per cubic foot, priced at SoCalGas’s non-baseline residential rate of 189.892¢ a therm from September 1, 2026 (baseline 142.208¢, which gives about $69 a day). Load B is set at 10.5 kW because that is the half-load point where Generac publishes fuel use. Both generator spec sheets show the pattern behind the last row: the lighter the load, the more fuel each kilowatt-hour takes. Solar recharge needs equipment built to keep running when the grid is down — a standard grid-tied system shuts off (why solar goes dark in an outage). To model your own loads, array and month, use the PSPS battery model or the battery sizing calculator.

• SGIP does not pay for generators. The 2026 SGIP Handbook lists “backup systems intended solely for emergency purposes” as ineligible equipment, and its storage incentives require a battery that runs in parallel with the grid (SGIP Handbook, Table 5). For batteries, SGIP’s ratepayer-funded budgets — including the general-market residential rebate — closed at the end of 2025; what remains are income-qualified Residential Solar and Storage Equity budgets, several on a waitlist (SGIP program metrics). Details in our SGIP guide.
• SCE offers up to $800 toward a qualifying portable generator and up to $200 toward a portable power station if you live in a PSPS-affected area; the larger generator amounts go to Medical Baseline, CARE and FERA customers (SCE backup power).
• PG&E pays up to $300 per account, plus up to $200 for CARE or FERA customers, toward a CARB-compliant portable generator on its qualified list or a 290–1,000 Wh portable battery, for customers in Tier 2 or 3 fire-threat districts, high-fire-risk areas or on EPSS circuits; apply within 12 months of purchase or by December 31, 2026 (PG&E rebate).
• Federal: the 30% Residential Clean Energy Credit ended for expenditures after December 31, 2025 (what changed).
• LADWP, Glendale, Burbank and Pasadena customers are outside the SCE and PG&E programs — check your own utility (LADWP incentives).

CARB. Under California’s small off-road engine rules, new portable-generator engines (spark-ignition, 25 hp or less) face zero smog-forming-emission standards from model year 2028, although manufacturers may keep certifying gasoline engines with emission credits through 2032. The rules do not touch generators already sold and in use, and larger portables and stationary standby units are outside them (CARB fact sheet, CARB FAQ). Buy a CARB-compliant (50-state) model: some popular ones are not sold here — Honda lists its EU2200i as “not for sale in California” (Honda) — and PG&E’s rebate requires CARB compliance. U.S. EPA authorized the rules in January 2025 and in June 2026 sent that authorization to Congress for review, so the federal status may change.

Air permits. Stationary engines fall to local air districts. In the South Coast AQMD, which covers most of the Los Angeles area, an engine with a manufacturer’s rating of 50 brake horsepower or less is exempt from an air permit (Rule 219) — ask the installer for the engine’s bhp rating. Your city’s building, electrical and gas-piping permits still apply.

Connecting to the house. State law allows a portable generator onto house wiring only after the main switch has isolated the home from the grid, and a permanently connected one only through a double-throw (transfer) switch; anyone running a generator connected to a home’s wiring must tell the utility where it is. Violations are misdemeanors, with fines up to $500 (Health & Safety Code §119075, §119085, §119090). SCE’s advice is to plug appliances into a portable unit with heavy-duty outdoor cords and to have a licensed electrician install a transfer switch for anything wired in (SCE generator safety). A battery needs an electrical permit and utility interconnection like any solar-plus-storage install.

About 100 people die in the U.S. each year from carbon monoxide produced by portable generators, according to the Consumer Product Safety Commission. Its rules: run a generator outside only, at least 20 feet from the house, with the exhaust pointed away; never inside a home, garage, basement, crawlspace or shed; put battery-backed CO alarms on every level; and choose a generator with a CO shut-off (Honda’s CO-MINDER is one). A battery has no exhaust — its safety questions are listing, location and code, covered in home battery safety.

It works when the system is designed for it. Some battery systems are built to manage a generator alongside solar and the grid — FranklinWH’s aGate is one (battery comparison) — while others have no generator input. Get generator support confirmed in writing before you buy, and do not improvise the connection: the transfer-switch law above still applies.

Choose a battery if your outages are PSPS-style events measured in hours to a few days, you have or plan to add solar, and you want backup that switches on by itself and also trims your bill. Choose a standby generator if you must keep central air, a well pump or other heavy loads running through multi-day outages. Choose a portable generator if the budget is tight and you can refuel it safely outdoors. For whole-house versus essential-circuit backup, see whole-home vs critical-loads backup; for battery models, Powerwall vs Enphase vs FranklinWH; for prices, what a home battery costs.

Figures on this page come from the primary sources below and, where noted, from Cali Energy calculations using the stated assumptions. Rates, incentives, and program terms change; each was verified September 28, 2026.

1. Generac — Guardian 20/22/24 kW spec sheet (fuel use at half and full load, sound levels, exercise, oil interval)
2. Generac — Backup generator installation (average installed cost $8,000–16,000 including the generator)
3. Honda — EU3200i specifications (MSRP, 1.2 gal tank, run time, noise, 50-state model)
4. Honda — EU7000iS specifications (MSRP, 5,500 W rated, 120/240 V)
5. Honda — EU2200i specifications ("not for sale in California")
6. Tesla — Powerwall 3 datasheet (13.5 kWh, 11.5 kW, operating noise)
7. Enphase — IQ Battery 5P datasheet (3.84 kVA, natural convection, noise)
8. Lawrence Berkeley National Laboratory — U.S. Distributed Solar and Storage 2025 Data Update (paired-storage price premium, median battery size)
9. EIA — Weekly California regular gasoline retail price
10. EIA — 2024 average monthly residential consumption by state (Table 5A)
11. SoCalGas — Schedule GR residential rates effective September 1, 2026 (tariff book update)
12. SCE — Solar Billing Plan export values by start year
13. SCE — Schedule NBT (Energy Export Bonus Credit by vintage)
14. SCE — Solar Billing Plan sample bill (June–July 2026)
15. SCE — Backup power solutions (portable generator and power station rebates)
16. SCE — Emergency preparedness and generator safety
17. PG&E — Generator & Battery Rebate Program
18. SCE — 2025 PSPS Post-Season Report (CPUC R.18-12-005)
19. SGIP — 2026 Handbook, Table 5 equipment eligibility (resources page)
20. SGIP — Program metrics (budget status)
21. SGIP — Public announcements (ratepayer-budget deadline, AB 209 budgets)
22. CARB — Authorization of the Small Off-Road Engine regulations (fact sheet, August 2026)
23. CARB — Small Off-Road Engine regulations FAQ
24. CPSC — Carbon monoxide safety tips for portable generators
25. California Health and Safety Code §119075 (generator connection)
26. California Health and Safety Code §119085 (notify the utility)
27. California Health and Safety Code §119090 (penalty)
28. South Coast AQMD — Rule 219, equipment not requiring a written permit
29. IRS — Residential Clean Energy Credit