People shop for a generator the way they shop for a ladder: by size. That is the wrong first question. The first question is what kind of outage you are solving for, because the four main categories of backup power are not competing products so much as answers to different problems.
1. Standby generators
A standby generator is a permanently installed engine on a concrete or composite pad outside the house, wired to an automatic transfer switch and fed by natural gas or a propane tank. When the utility drops, the controller waits a few seconds to confirm the outage, starts the engine, and the transfer switch moves your loads from the grid to the generator. You may not even wake up.
Good for: homes with well water, medical equipment, sump pumps in a wet basement, home offices, freezers full of food, and anyone in a region where multi-day outages are routine.
The costs: the equipment is a fraction of the project. You are also paying for the pad, the transfer switch, gas piping and its pressure calculation, an electrical permit, and usually an inspection. Expect a real quote to be several times the price tag on the generator itself.
The commitments: it self-tests weekly, which your neighbours will hear. It needs oil changes and filters on a schedule. It needs fuel supply that survives the event you bought it for, which is worth thinking about if you are in an earthquake zone where gas is shut off as a precaution.
2. Portable generators
The familiar wheeled frame with a gasoline engine, a fuel tank and a bank of outlets. Portables span roughly 1 kW to 12 kW, run on gasoline, propane or both (dual fuel), and cost less than a tenth of a standby installation.
Good for: occasional outages, job sites, tailgating, and people willing to trade convenience for money.
The catch is operational. Someone has to go outside in the storm, roll it out, start it, run cords or throw a transfer switch, and refuel it every 8 to 12 hours, including in the middle of the night. And it must run outdoors, away from the house, every single time. The U.S. Fire Administration's guidance is blunt about this: generators belong outdoors in a well-ventilated area, away from doors, windows and vents, never in a garage even with the door open.
3. Inverter generators
An inverter generator is still an engine, but instead of turning a fixed-speed alternator it produces DC and then reconstructs a clean AC sine wave electronically, using the same principle as any other power inverter. Two consequences follow, and they are the whole reason the category exists.
First, the engine no longer has to hold 3,600 rpm to keep the frequency right, so it can throttle down when the load is light. That makes inverter units dramatically quieter and more fuel efficient at partial load. Second, the output waveform has low harmonic distortion, so sensitive electronics are happy.
Good for: camping and RVs, running a home office, anywhere noise rules apply, and any load list dominated by electronics. Many models can be paralleled: two 2,200 watt units linked together behave like one 4,000 watt unit and are far easier to carry one at a time.
The trade: roughly twice the price per watt of a conventional portable, and the electronics are one more thing that can fail.
4. Battery power stations and home battery backup
A battery power station is a lithium battery, an inverter and a charge controller in one box. It stores energy rather than making it, so its rating has two numbers that matter: capacity in watt-hours and output in watts. There is no engine, no fuel, no exhaust and no noise, which means it is the only category on this list that is safe to operate inside the house.
Good for: apartments and condos where an engine is not an option, medical devices like CPAP machines, keeping the fridge and the internet alive through outages of a few hours to a day, and pairing with solar so the outage clock resets every morning. If you are thinking about the solar half seriously, the general concept is home energy storage, and the Department of Energy's Energy Savings Hub covers the incentives that often apply to it.
The limit is energy, not power. A 2 kWh unit running a 700 watt refrigerator duty-cycling at roughly 35 percent gives you about eight hours. Cover a whole house for three days and you are into expandable systems with multiple battery modules, which start to approach standby generator money, though without the permits, the gas line or the noise.
Side by side
| Standby | Portable | Inverter | Battery | |
|---|---|---|---|---|
| Starts by itself | Yes | No | No | Yes (with a transfer device) |
| Runtime limit | Fuel supply | Tank, then refuel | Tank, then refuel | Stored energy, then recharge |
| Can it run indoors | No | No | No | Yes |
| Noise | Loud, weekly self-test | Loud | Quiet | Silent |
| Install required | Electrician and permits | Optional transfer switch | Optional transfer switch | None for plug-in use |
| Maintenance | Scheduled service | Oil, fuel, stabilizer | Oil, fuel, stabilizer | Essentially none |
The combination most people end up with
The honest answer for a lot of households is two devices rather than one. A battery power station covers the first several hours silently and indoors, handles every short outage without anyone going outside, and keeps the medical equipment and the router running while you decide whether the outage is serious. A fuel generator handles the long tail: day two, day three, the well pump and the heat. Batteries also recharge from a running generator, so the engine runs for two hours to refill the battery and then shuts off, which is quieter and burns less fuel than running it all night.
Pick by outage pattern
- Outages of a few hours, a few times a year: battery power station, or a small inverter generator.
- Outages of a day or two, every winter: a mid-size portable plus a transfer switch, or a battery sized for the essentials.
- Multi-day outages, well water or a medical need: standby generator, and stop reading comparison articles.
- Apartment or condo: battery only. An engine is not a legal or safe option on a balcony.
If you are leaning toward a standby unit, get at least three quotes and make sure each one includes the load calculation, the transfer switch model, the gas line work and the permit. That is where quotes differ, not in the generator.