The right home battery size depends on two things: which circuits you want to keep on during an outage, and how long outages last where you live. Here's how to work it out, with real numbers for the most common setups.
Step 1: Decide what to back up
Most homeowners choose one of two approaches:
- Essentials backup: fridge and freezer, lights, internet, furnace fan, well or sump pump, a few outlets. Usually 6–12 kWh per day.
- Whole-home backup: everything, including the range, dryer and AC. Usually 20–40 kWh per day, and it needs a larger inverter.
Step 2: Estimate essential loads
| Load | Approx. kWh per day |
|---|---|
| Refrigerator + chest freezer | 2.0–2.5 |
| Gas furnace blower | 2.0–4.0 (winter) |
| Sump pump | 0.5–2.0 (storms) |
| Well pump | 1.0–2.0 |
| LED lights, Wi-Fi, phones, TV | 1.0–1.5 |
| Microwave, coffee maker | 0.5–1.0 |
A typical essentials total is around 8–10 kWh per day.
Step 3: Multiply by how long outages last
Battery size ≈ daily essential load × hours of outage ÷ 24 ÷ 0.9 (usable capacity for LiFePO4).
- 8-hour outage, 9 kWh/day: about 3.5 kWh — a single 5kWh battery covers it.
- 24-hour outage: about 10 kWh.
- 2–3 day outage after a hurricane or ice storm: 20–30 kWh, or a smaller battery recharged by solar during the day.
Adding solar changes the math: with 4–6 kW of panels recharging the battery each day, a single 14.34kWh battery can keep essentials running for days.
Quick guide
| Goal | Battery size |
|---|---|
| Ride out short outages, essentials only | 5–10 kWh |
| Overnight + next day, essentials | 14–15 kWh |
| Multi-day, essentials (or whole home for a day) | 28–30 kWh |
| Whole home, multi-day | 40 kWh+ plus solar |
Battery options
Prices as of October 2026.
- GSL Energy 14.34kWh 48V LiFePO4 battery — $2,999.99. The lowest cost per kWh in our range (about $209/kWh), with 13.6kWh usable and an IP65 outdoor-rated enclosure for a garage, barn or sheltered exterior wall. One covers a full day of essentials; stack up to 16 for multi-day backup.
- Growatt ALP 5kWh 48V LiFePO4 battery — $1,699.99. A stackable module for smaller systems or when you want to start small and add later.
- Growatt 11.4kW Whole Home Backup Power System — from $10,999.99. A Growatt MIN 11.4kW hybrid inverter, a 10kWh or 20kWh APX high-voltage battery and an automatic transfer switch in one matched system, for homes with heavy loads.
- Growatt 3.8–6kW Partial Home Backup Power System — from $7,999.99. A 3.8kW or 6kW Growatt hybrid inverter, a 5kWh or 10kWh APX battery and a transfer switch, sized to carry your essential circuits.
See all options in home solar batteries.
Don't forget the inverter
The battery stores energy; the inverter decides how much you can draw at once. A 48V battery needs a 48V hybrid or off-grid inverter rated for your peak load — typically 6–12 kW split-phase for a home. Check that the battery is on the inverter's compatibility list so they communicate properly.
FAQ
How long will a 14.34kWh battery run my house?
It has 13.6kWh usable, so about 36 hours on essentials at 9 kWh/day, or roughly half a day of normal whole-home use.
Is a home battery better than a generator?
A battery is silent, needs no fuel and switches over instantly. A generator runs indefinitely on fuel. Many homeowners pair a battery with solar and keep a small generator for long winter outages.
Is LiFePO4 safe indoors?
LiFePO4 is the most thermally stable lithium chemistry and is widely installed in garages and utility rooms. Follow local code and the manufacturer's clearances.
Is there a federal tax credit for home batteries?
The federal residential clean energy credit (Section 25D) does not apply to systems paid for after December 31, 2025 (IRS). Some states and utilities still offer battery rebates or backup-power programs, so check what applies where you live.
Want help choosing? Tell us what you want to back up and we'll size it for you.