The question is usually framed as which to buy. I think the more useful framing is what each one actually is.
A generator is an engine that makes electricity for as long as you feed it. Its constraint is fuel, and its costs are noise, exhaust, maintenance and a genuine carbon-monoxide hazard.
A battery is a fixed quantity of stored energy. Its constraint is capacity, and it has essentially none of those costs.
Side by side
| Petrol generator | Battery power station | Notes | |
|---|---|---|---|
| Runtime | Indefinite with fuel | Fixed by capacity | The core difference |
| Refuelling | Minutes | 1–2.5 hours on a wall, or a sunny day | My measured recharges |
| Indoor use | Never | Safe | CO kills |
| Noise | 60–75 dBA typical | 34–45 dBA at ~500 W | My measurements at 1 m |
| Maintenance | Oil, filters, fuel stabiliser | None | |
| Cold starting | Can be difficult | Discharges fine | Batteries won't charge when frozen |
| Emissions | Exhaust | None | |
| Upfront cost | Lower per watt | Higher | |
| Cost over 10 years | Fuel + servicing | Effectively nothing | |
| Powers 240 V | Commonly | Rarely | Two of the 11 I tested |
| Fuel storage | Required | None | Petrol degrades in months |
- Petrol generator
- Indefinite with fuel
- Battery power station
- Fixed by capacity
- Notes
- The core difference
- Petrol generator
- Minutes
- Battery power station
- 1–2.5 hours on a wall, or a sunny day
- Notes
- My measured recharges
- Petrol generator
- Never
- Battery power station
- Safe
- Notes
- CO kills
- Petrol generator
- 60–75 dBA typical
- Battery power station
- 34–45 dBA at ~500 W
- Notes
- My measurements at 1 m
- Petrol generator
- Oil, filters, fuel stabiliser
- Battery power station
- None
- Notes
- Petrol generator
- Can be difficult
- Battery power station
- Discharges fine
- Notes
- Batteries won't charge when frozen
- Petrol generator
- Exhaust
- Battery power station
- None
- Notes
- Petrol generator
- Lower per watt
- Battery power station
- Higher
- Notes
- Petrol generator
- Fuel + servicing
- Battery power station
- Effectively nothing
- Notes
- Petrol generator
- Commonly
- Battery power station
- Rarely
- Notes
- Two of the 11 I tested
- Petrol generator
- Required
- Battery power station
- None
- Notes
- Petrol degrades in months
Where a generator is the right answer
Outages lasting days. This is decisive. The largest battery I tested, the EcoFlow Delta Pro 3, ran a fridge alone for 80 hours, and a fridge, freezer and router for 31. A generator with fuel runs for a week. If you live somewhere hurricanes or ice storms take the grid out for five days, a battery alone isn't the answer.
Large 240 V loads. Well pumps, electric ranges, central air. Only two of the eleven batteries I tested provide 240 V — the Delta Pro 3, which ran my well pump, and the Anker SOLIX F3800 Plus. Neither will run central air for long.
Lowest cost per watt today. A generator producing 5,000 W costs far less than a battery storing 5 kWh.
Where a battery is the right answer
Outages lasting hours. Which is most of them. The 2 kWh units I tested ran a fridge and router for 39 to 41 hours, silently, with nothing to start and no fuel gone stale.
Anything indoors. Apartments, medical equipment, a CPAP beside the bed. A generator simply isn't an option.
No warning. On UPS duty, every battery I tested switched over in 30 ms or less, and the best in 10 ms — the fridge doesn't notice and a computer doesn't reboot. A generator needs someone to go outside and start it.
Neighbours, and sleep. I measured every battery at one metre: 34 to 45 dBA at about 500 W, and 44 to 60 dBA flat out at several kilowatts. A generator at 60–75 dBA is a conversation you'll have with the people next door at 2 a.m.
No maintenance. A generator that has sat for two years with stale fuel in the carburettor frequently won't start. That's the most common way backup generators fail: not during use, but at the moment they're needed.
The honest recommendation: often both
For most households facing multi-day outages, the sensible arrangement is a battery for the first day and a generator for the rest.
The battery handles the common case silently and automatically — the four-hour cut where nobody even goes outside. The generator handles the rare multi-day event, and can recharge the battery during the day so the battery covers the night with the engine off.
Several of the units I tested accept generator input directly for exactly this reason.
What each costs over ten years
An illustrative comparison for a household with roughly four outage days a year:
| Generator | Battery | |
|---|---|---|
| Purchase | ~$800 | ~$1,200 |
| Fuel, 10 years | ~$400 | $0 |
| Servicing, 10 years | ~$500 | $0 |
| Replacement in period | Possible | No — rated 3,000–6,000 cycles |
| Approximate total | ~$1,700 | ~$1,200 |
These figures are illustrative rather than sourced, and they'll move with your fuel prices and usage. The structural point is robust: a generator's purchase price is the start of its cost, and a battery's is close to all of it.
Solar changes the argument
The one thing a generator can't do is refuel itself.
A battery with panels recovers energy every day the sun is up — 550 to 1,050 watt-hours a day from two 100 W panels, and far more from a real array.[1] In my testing, a 2,400 W roof array pushed 2,480 W into the Delta Pro 3, and the F3800 Plus accepted 3,050 W — enough to refill either in a single good day.
That doesn't match a generator's output, but it substantially narrows the runtime gap that is the generator's main advantage — with no fuel, no noise and no exhaust. See solar recharge in practice for realistic numbers.
FAQ
Is a battery or a generator better for home backup?
A battery for outages of hours, which is most of them — silent, safe indoors, automatic, no maintenance. A generator for outages of days, or for large 240 V loads. Many households are best served by a battery for the common case and a generator for the rare one.
Can I run a generator in my garage?
No. Never, even with the door open. Generators produce carbon monoxide, which is colourless, odourless and lethal. Generators run outdoors, well away from windows, doors and air intakes.
How long will a battery last in an outage compared to a generator?
In my drills, a fridge and router ran 21 to 23 hours on a 1 kWh battery and 39 to 41 hours on a 2 kWh one. The largest, the EcoFlow Delta Pro 3, ran a fridge alone for 80 hours. A generator runs as long as you have fuel.
Can I charge a power station with a generator?
Yes, and it's the best way to use both. Run the generator for a few hours in daylight to recharge the battery and cover heavy loads, then switch it off and run off the battery overnight.
How quiet is a battery compared to a generator?
At about 500 W, the batteries I tested measured 34 to 45 dBA at one metre — the quietest barely above a silent room. A typical portable generator is 60–75 dBA.
For more on outage runtimes, see running a fridge through an outage, or the best power stations for home backup.
Sources
- OutdoorGearLab. Jackery SolarSaga 100 W panel — measured output. Independent lab test · accessed 5 September 2026