A home battery stores 10 to 15 kWh or more per unit, switches over silently and pairs with solar, but runtime is limited by capacity. A standby generator runs on natural gas or propane for days and starts automatically. A portable generator is cheapest per watt but must run outdoors and connect through a transfer switch or interlock. A power station suits a few essentials. Size any of them to your critical loads.
The right backup depends on what you need to keep running and for how long. Start with a list of essential loads, then compare systems.
Side by side
| Home battery | Standby generator | Portable generator | Power station | |
|---|---|---|---|---|
| Energy | About 10 to 15 kWh per unit, expandable | Unlimited while fuel lasts | Limited by tank size | About 1 to 5 kWh |
| Switchover | Automatic, near seamless | Automatic, seconds | Manual | Manual |
| Fuel | Grid or solar | Natural gas or propane | Gasoline, propane or dual fuel | Grid, solar or car |
| Noise | Silent | Moderate | Loud | Silent |
| Indoor use | Yes, per install code | No, outdoor unit | Never | Yes |
| Connection | Installed with panel or gateway | Automatic transfer switch | Transfer switch or interlock | Cords, or a transfer panel on some models |
Size your loads
| Load | Typical running watts |
|---|---|
| Refrigerator | 100 to 800 (cycles on and off) |
| Furnace blower | 300 to 800 |
| Sump pump | 800 to 1,500 |
| Well pump | 1,000 to 2,500 |
| Internet and router | 20 to 60 |
| LED lights | 10 each |
Motors draw a surge at start-up two to three times their running watts. Check the nameplates on your appliances.
Safety and certification
Look for UL 9540 listing on home battery systems and UL 1741 on inverters. Generators must connect through a transfer switch or interlock; never backfeed. Portable generators should have CO shutoff and run outdoors.
Which to choose
Choose a battery if you have or plan solar and want silent, automatic backup. Choose a standby generator for long outages with natural gas available. Choose a portable generator for cost, accepting manual setup. Choose a power station for apartments or a short list of devices.
EV owners should also read our Level 2 charger guide for panel capacity. Browse power and energy.
Common questions
How much backup power do I need?
List the loads you must run, add their watts for peak power and multiply by hours for energy. A fridge, lights, internet and a furnace blower need far less than a whole house.
Can I plug a portable generator into a wall outlet?
No. Backfeeding through an outlet is dangerous and illegal. Use a transfer switch or an approved interlock installed by an electrician.
Where should a portable generator run?
Outdoors, well away from doors, windows and vents. The CDC advises at least 20 feet from the home because of carbon monoxide.
Does a home battery work without solar?
Yes. It charges from the grid and covers outages, though solar lets it recharge during a long outage.