How much battery backup does a house need?
Start with your monthly electricity use from your utility bill. Divide by 30.4 for a daily average, then decide how many hours of outage you want to cover. If you have solar panels, they recharge the battery during the day.
Battery size by monthly use (whole home, no solar)
| Monthly use | 12 h outage | 24 h outage | 72 h outage |
|---|---|---|---|
| 300 kWh | 5.5 kWh | 11.0 kWh | 32.9 kWh |
| 600 kWh | 11.0 kWh | 21.9 kWh | 65.8 kWh |
| 900 kWh | 16.4 kWh | 32.9 kWh | 98.7 kWh |
| 1,200 kWh | 21.9 kWh | 43.9 kWh | 131.6 kWh |
| 1,800 kWh | 32.9 kWh | 65.8 kWh | 197.4 kWh |
Backing up only essentials (fridge, lights, Wi-Fi, furnace fan, sump pump) usually needs just 30–40% of these numbers. That's often the most cost-effective approach.
Plug-in vs. installed home batteries
| Plug-in power station systems | Installed home batteries | |
|---|---|---|
| Examples | Anker SOLIX F3800 Plus, EcoFlow DELTA Pro | Tesla Powerwall, Enphase IQ, FranklinWH |
| Installation | DIY; optional transfer switch | Licensed installer required |
| Typical capacity | 3.6–50 kWh (expandable) | 10–15 kWh per unit, stackable |
| Switchover | Manual or via transfer switch | Automatic (seamless) |
| Incentives | Usually not eligible for tax credits | Often eligible for local incentives |
| Portability | Take it camping or move it | Fixed |
Peak power matters as much as kWh
A battery with plenty of kWh can still trip if too much starts at once. Central AC, well pumps and electric ranges need high peak output: 8–12 kW for whole-home backup. Plug-in units deliver 3.6–6 kW each; many can be paired for 240 V and more power.
Frequently asked questions
How many kWh do I need to power my house for a day?
The average US home uses about 30 kWh per day (≈ 900 kWh/month). Covering a full day therefore needs around 30 kWh of battery, or about 10–12 kWh if you back up essentials only.
How long will a 10 kWh battery power a house?
With essentials only (≈ 400–600 W average) a 10 kWh battery lasts about 15–22 hours. Whole-home use at 1.2 kW average lasts about 7–8 hours.
Is a home battery worth it without solar?
For outage protection, yes, especially with medical devices or a sump pump. Financial payback mostly comes with solar or time-of-use electricity rates.
Can a portable power station back up my house?
Large units like the Anker SOLIX F3800 Plus or EcoFlow DELTA Pro can power home circuits through a transfer switch or home panel kit installed by an electrician.