How long will a battery keep your house running?

Choose what must stay on and pick a battery. Then watch 72 hours of a blackout play out, including whether solar panels can recharge it. A fridge alone uses about 1.4 kWh a day; central air uses twenty times that.

A single candle burning in a dark room during a power cut — A fridge, a furnace fan and Wi-Fi: the three things most people want in a blackout.

1 · What must keep running?

Appliance	Watts	Hours/day	kWh/day
Refrigerator			1.4
Modem + Wi-Fi router			0.5
LED lights (6 rooms)			0.3
Phones & laptop charging			0.2
Total			2.3

“Hours/day” is equivalent full-power hours: a fridge's compressor runs ~9 of 24 hours. Check appliance nameplates for your numbers.

2 · Which battery?

How many

Charge when outage starts

100%

3 · Solar to recharge it? (optional)

Solar array

none

Tesla Powerwall 3 · 2.3 kWh/day of loads

Runs with no sun5.5days13.5 kWh available

With solar—add solar + location

Everything on at once0.3kWlimit 11.5 kW continuous · start-up peak ≈0.6 kW

ChargeLoads not coveredNight

Refrigerator start-up can briefly need ~0.5 kW. Check the battery's surge rating.

Outage starts 6 pm. Discharge efficiency 94% ( 89%). Capacities are manufacturer figures; verify the current datasheet.

Add this to a full solar plan →

Battery runtime without any sun

Hours of runtime starting full, no solar recharge. Typical appliance loads; your appliances will differ.

Battery	Usable	Fridge only 1.3 kWh/day	Keep the food cold & lights on 2.3 kWh/day	Essentials + furnace fan + TV 6.9 kWh/day	Rural: essentials + well + sump 6.0 kWh/day	Summer outage with window AC 10.8 kWh/day
Tesla Powerwall 3	13.5 kWh	9.4 days	5.5 days	44 h	2.1 days	28 h
FranklinWH aPower 2	15 kWh	10.5 days	6.1 days	2.0 days	2.3 days	31 h
Enphase IQ Battery 5P	5 kWh	3.5 days	2.1 days	16 h	19 h	11 h
SolarEdge Home Battery	9.7 kWh	6.8 days	4.0 days	32 h	37 h	20 h
Generic 10 kWh home battery	10 kWh	7.0 days	4.1 days	33 h	38 h	21 h
EcoFlow DELTA Pro Ultra (1 battery)	6.1 kWh	3.8 days	2.2 days	18 h	21 h	12 h
Anker SOLIX F3800	3.84 kWh	2.4 days	34 h	11 h	13 h	7 h
Jackery Explorer 2000 Plus	2.04 kWh	31 h	18 h	6 h	7 h	4 h
EcoFlow DELTA 2 (1 kWh class)	1.02 kWh	15 h	9 h	3 h	3 h	2 h

Runtime = usable kWh × discharge efficiency ÷ average load. Whole-home AC loads can exceed a single battery's power limit even when energy is available. Specs: manufacturer datasheets (verify current versions).