HomeBlogBlogLiFePO4 Batteries for Whole-Home Backup: How Many?

LiFePO4 Batteries for Whole-Home Backup: How Many?

How many LiFePO4 batteries to power a house?

The number of LiFePO4 (lithium iron phosphate) batteries needed to power a house depends on three things: how much energy the home uses per day (kWh), how long you want to run without the grid (hours or days), and how much of each battery’s capacity is actually usable after inverter losses and reserve margin.

Step 1: Estimate your home’s daily energy use

Check a recent electric bill or your utility app. Many U.S. homes use roughly 20–35 kWh per day, but an efficient apartment might be 8–15 kWh and a larger home with heavy HVAC can exceed 40 kWh.

Step 2: Convert battery capacity to usable energy

Battery capacity is usually listed in watt-hours (Wh) or kilowatt-hours (kWh). As a practical planning number, assume 85–90% of the rated capacity is usable after inverter/charging losses and a small buffer. For example, a 2,764 Wh (2.764 kWh) LiFePO4 expansion battery might deliver about 2.3–2.5 kWh of usable energy depending on your system and settings.

For a deeper look at how a 2,764Wh LiFePO4 expansion battery performs in real runtimes, see: https://ellixuro.com/guide-2764wh-lifepo4-expansion-battery-power-stations-runtime/

Step 3: Use a simple sizing formula

Batteries needed ≈ (Daily kWh × Days of backup) ÷ (Battery kWh × 0.85)

Example: If you use 30 kWh/day and want 1 day of backup using 2.764 kWh batteries: 30 ÷ (2.764 × 0.85) ≈ 12.8, so plan on about 13 batteries.

Don’t forget power (watts), not just energy (kWh)

Energy determines how long you can run; power determines what you can run at once. Big loads like central A/C, electric dryers, ovens, and well pumps may require a larger inverter and higher surge capability—sometimes pushing you toward a whole-home battery system even if the kWh math looks manageable.

FAQ

Can a LiFePO4 battery run an air conditioner?

Yes, but it depends on the A/C’s starting surge and running watts and your inverter’s surge rating. Many central A/C units need a high-surge inverter and a larger battery bank to run for meaningful hours.