How big a battery do you need to run a refrigerator during an outage?
A typical refrigerator needs a battery of about 1.48 kWh for one day and 4.44 kWh for three, with an inverter that can supply 0.15 kW running and 1.20 kW for the start-up surge. Those are the calculator’s default fridge figures, so replace them with your own fridge’s before you buy.
The numbers for one refrigerator
A battery has to pass three tests: enough energy (kWh) for the whole outage, enough continuous output (kW) for what is running, and enough surge (kW) for the moment a compressor starts. For one refrigerator the calculator’s defaults are 150 W running, 1,200 W of surge and 8 hours a day.
| Outage | Energy used (kWh) | Battery needed (kWh) | Continuous (kW) | Surge (kW) |
|---|---|---|---|---|
| 1 day | 1.20 | 1.48 | 0.15 | 1.20 |
| 3 days | 3.60 | 4.44 | 0.15 | 1.20 |
| 7 days | 8.40 | 10.37 | 0.15 | 1.20 |
How the calculator gets them
150 W × 1 × 8 h ÷ 1,000 = 1.20 kWh a day
That daily energy is multiplied by the days of outage, then divided by the 0.90 depth of discharge and the 0.90 inverter efficiency, which together are 0.81. One day is 1.20 ÷ 0.81 = 1.48 kWh. Three days is 3.60 ÷ 0.81 = 4.44 kWh. The eight hours is the calculator’s planning assumption that a fridge’s compressor runs about a third of the day.
What changes the answer
Length of outage. Energy scales with days, so seven days needs 10.37 kWh. Output does not: the fridge still needs the same 0.15 kW.
Solar. The calculator estimates recharge as panel kW × peak sun hours × 0.80. One kilowatt of panels at the default 4.5 hours gives 3.60 kWh a day, which covers the fridge’s 1.20 kWh. A three-day outage then needs only the one-day battery, 1.48 kWh. Weather and season change real recharge, so edit the sun hours for your outage.
Surge. The start-up draw is 8 times the running draw. If anything else is plugged in, its running watts are added to that surge, so a battery that looks big enough for the fridge alone can trip with a second load.
Your own fridge. The Federal Trade Commission explains that the yellow EnergyGuide label on most home appliances tells you how much energy the appliance uses. Use your fridge’s label or manual in place of the defaults.
Which products cover three days
All six products in the calculator’s shortlist cover the three-day example. They differ in how many expansion batteries they need to reach 4.44 kWh.
| Product | Expansion batteries | Capacity (kWh) |
|---|---|---|
| Anker SOLIX F3800 Plus | 1 | 7.68 |
| EcoFlow DELTA Pro Ultra | 0 | 6.14 |
| EcoFlow DELTA Pro 3 | 1 | 8.19 |
| Jackery Explorer 5000 Plus | 0 | 5.04 |
| Bluetti Apex 300 | 1 | 5.53 |
| Tesla Powerwall 3 (installer only) | 0 | 13.50 |
The calculator’s shortlist shows the full checks for each product, including the price and the date it was read.
Sources and what we left out
- Federal Trade Commission, How To Use the EnergyGuide Label To Shop for Home Appliances.
- Product capacities, from each maker’s own page: Anker SOLIX F3800 Plus, EcoFlow DELTA Pro Ultra, EcoFlow DELTA Pro 3, Jackery Explorer 5000 Plus, Bluetti Apex 300 and Tesla Powerwall 3. Each was read between 2026-10-03 and 2026-10-04.
- Depth of discharge, inverter efficiency, the solar derating and the fridge figures are the calculator’s own settings, shown on its page.
We did not find one source we could cite for a default refrigerator wattage, so the 150 W, 1,200 W and 8 hours are planning defaults, not measurements of your fridge. A licensed electrician should confirm any panel, transfer switch or 240 V work.