How long will a battery run my refrigerator during an outage?

A typical fridge draws about 150W but cycles on and off, averaging closer to 60W over time. A 2 kWh battery (about 1.7 kWh usable) would run just the fridge for well over a day, since it isn’t drawing power continuously. Add lights, WiFi, and phone charging and that drops to under a day — this calculator shows the exact runtime for the loads you pick.

How do I size a backup battery?

Add up the running watts of everything you need during an outage, then divide your battery’s usable energy (roughly 85% of its rated kWh) by that load to get hours of runtime. Appliances that cycle, like fridges and pumps, run much longer than their nameplate watts suggest because they’re only on part of the time.

What can a plug-in solar battery actually power?

Most balcony / plug-in solar batteries (1–5 kWh) are sized for essentials: refrigeration, lights, WiFi, device charging, and a CPAP or medical device. They are not meant to run central AC, electric heat, a dryer, or an oven, which draw far more than a small battery can sustain.

Energy Advisor

How long will your battery keep the lights on?

Whether it's a plug-in solar battery or a portable power station, the real question in an outage is: how long does it last? Set your battery size, pick the essentials you'd run, and see the runtime — with cycling appliances like fridges handled honestly, not just nameplate watts.

Battery size (kWh)

Usable energy is about 85% of the rated size, after inverter losses and reserve. Common plug-in solar batteries are 1–5 kWh; portable power stations 0.5–2 kWh.

Realistic runtime

8.3 hr

with normal cycling

If everything ran nonstop

4.5 hr

worst case

Selected load

205W avg

380W peak

Check the loads you'd actually run during an outage:

Load	Power	Avg draw
Refrigerator Cycles on and off — keep the door shut.	150W	60W
Chest / upright freezer Holds for ~24h unopened even without power.	100W	40W
WiFi router + modem Stays online if your ISP line is up.	20W	20W
Phone + laptop charging Intermittent; small but essential.	50W	25W
LED lights (a few rooms) Whole-home LED is still very low draw.	60W	60W
CPAP machine (overnight) Run without the heated humidifier to save power.	60W	60W
Medical / monitoring device Check your device’s exact rating.	100W	100W
Television + streaming box Comfort load; easy to cut to extend runtime.	120W	120W
Box / ceiling fan Cheap comfort in a heat wave.	75W	75W
Microwave Big draw, but only minutes at a time.	1,000W	100W
Sump pump Critical in a storm; cycles with water level.	800W	240W
Well pump Runs only while water is being drawn.	1,000W	150W
Space heater Drains a battery fast — heat one small room only.	1,500W	900W
Window AC unit Heavy load; a fan is far gentler on the battery.	1,000W	600W

"Avg draw" folds in how often each load actually runs during an outage (a fridge compressor cycles; a light left on does not), which is why realistic runtime is longer than the worst-case nonstop figure. Estimates use typical wattages; your devices may differ. Large loads like central AC, electric heat, dryers, and ovens are intentionally excluded — small batteries can't sustain them.

Planning for outages or thinking about a battery?

Ask the free Energy Advisor how to size a battery, whether to add storage to a plug-in solar kit, or what's worth backing up.

Sizing a battery, honestly

Runtime is just usable energy ÷ average load. A battery's usable energy is about 85% of its rated kWh once you account for inverter losses and a reserve. The load is the trickier part: a refrigerator is labeled ~150W but only runs its compressor part of the time, so it averages closer to 60W. Lump everything at nameplate watts and you'll badly underestimate how long you'll last.

That's why a modest 2 kWh plug-in solar battery can carry the true essentials — fridge, a few lights, WiFi, phone charging, a CPAP — through a long evening or overnight, while it would be hopeless against central AC or electric heat. Match the battery to the loads that genuinely matter when the grid goes down, and if you have plug-in solar, the panel recharges it the next day.