Disclosure first: Mr. Legit Solar installs batteries and does not install standby generators. Weigh what follows accordingly. We have tried to write the version we would want to read if we were the customer, including the part where the generator wins.
They solve different problems
A standby generator is a machine that makes electricity from fuel. A battery is a container that stores electricity you already made. That difference determines almost everything else.
A generator's runtime is limited by fuel supply. On natural gas, that is effectively unlimited. On propane, it is however large your tank is. A battery's runtime is limited by stored energy, but if you have solar, it refills every morning for free.
Head to head
| Battery storage | Standby generator | |
|---|---|---|
| Installed cost | $12k–$20k per unit | $8k–$16k for 18–24 kW |
| Whole-home capable | Usually needs 2–3 units | Yes, from one unit |
| Multi-day outage | Yes, if paired with solar | Yes, if fuel holds |
| Switchover time | ~20 milliseconds, imperceptible | 10–30 seconds |
| Noise | Silent | 60–70 dB at the property line |
| Maintenance | None | Annual service, oil, exercise cycles |
| Saves money when the grid is up | Yes, on time-of-use rates | No |
| Works during a gas outage | Yes | Not on natural gas |
| Expected life | 10–15 years | 20–30 years with service |
When the generator is the better buy
We say this to customers regularly:
- You lose power for days at a time, several times a year. Ice storms, hurricanes, rural distribution lines. A battery sized for that is three or four units; a generator handles it for less.
- You need to run the whole house including central air, and you have no solar. Without solar to recharge it, a battery is just a very expensive short-duration UPS.
- You have a well pump, a septic pump and electric heat in a cold climate. Those loads are brutal on a battery and trivial for a generator.
- Your budget is $10,000 and you want whole-home resilience. A battery cannot deliver that at that price. A generator can.
When the battery is the better buy
- Your outages are short and occasional. Four hours, a few times a year. A generator that takes 20 seconds to start and needs annual servicing is overkill.
- You already have or are buying solar. This is the decisive one. Solar plus storage handles multi-day outages indefinitely, and the battery earns money the other 360 days a year.
- You are on a time-of-use rate with an expensive peak. A battery that charges at midday and discharges from 4–9pm has an economic case a generator can never have.
- Noise, emissions or fuel storage are a problem. Dense neighbourhoods, HOA rules, or simply not wanting a combustion engine ten feet from a bedroom window.
- You want it to work without you. No fuel to check, no starting, no exercise cycle. It just happens.
The combination nobody mentions
You can have both, and for some rural properties it is the right answer: solar and a battery handling daily economics and short outages, with a modest generator as the backstop for the multi-day event in February when the panels are under snow. FranklinWH in particular is built for this integration, and Powerwall and Enphase can coexist with a generator given a correctly configured transfer switch.
What you cannot do is let a generator and a grid-forming battery inverter fight over the same bus. That is an electrician problem, and it is the reason we insist on doing the transfer switch ourselves rather than inheriting one.
Our actual advice
If you are getting solar anyway, add storage. The incremental cost buys you resilience plus a daily economic return. If you are not getting solar and you need whole-home backup through long outages, buy the generator and do not let a solar company talk you out of it.