KeepCold

Refrigerator battery calculator

Pick your fridge and how long you need it. We’ll show a battery size and the closest matches.

How the 500 kWh example is calculated

Worked example, before you enter your own numbers

A refrigerator that uses 500 kWh per year averages 57.0776 W. The 10 W idle allowance is added first, so the AC-equivalent load is 67.0776 W. For a 2,048 Wh battery, the exact runtime is 23.3568 hours. Rounded to one decimal, that is about 23.4 hours. The minimum capacity for 24 hours is 2,104.4 Wh. That is 56.4 Wh more than 2,048 Wh, so this capacity does not cover the full 24-hour plan.

The equations are average watts = annual kWh × 1000 / 8760, AC-equivalent watts = average watts + idle watts, runtime = capacity × efficiency × (1 − reserve) / AC-equivalent watts, and minimum capacity = duration × AC-equivalent watts / (efficiency × (1 − reserve)). With the defaults that is runtime = capacity × 0.85 × 0.90 / (average watts + 10). JavaScript is not required to read this example.

On a narrow screen each battery is a full block. You do not need to scroll the page sideways.

Worked example for 500 kWh per year and 24 hours. Out-of-stock models stay on the comparison page.
Model Capacity Continuous Published surge Planning result Availability Link
EcoFlow DELTA 3 Ultra Plus 3,072 Wh 3,600 W 7,200 W Planning runtime 35.0 hours. Published capacity meets this duration on these assumptions. That is not a guarantee the appliance will run. preorder See preorder details at EcoFlow (opens in a new tab)
Jackery HomePower 3000 3,072 Wh 3,600 W 7,200 W Planning runtime 35.0 hours. Published capacity meets this duration on these assumptions. That is not a guarantee the appliance will run. preorder See preorder details at Jackery (opens in a new tab)
EcoFlow DELTA 3 Max Plus + Smart Extra Battery 4,096 Wh 3,000 W 6,000 W Planning runtime 46.7 hours. Published capacity meets this duration on these assumptions. That is not a guarantee the appliance will run. preorder See preorder details at EcoFlow (opens in a new tab)
EcoFlow DELTA 3 Ultra Plus + DELTA 3 Max Plus Extra Battery 5,120 Wh 3,600 W 7,200 W Planning runtime 58.4 hours. Published capacity meets this duration on these assumptions. That is not a guarantee the appliance will run. preorder See preorder details at EcoFlow (opens in a new tab)
Jackery Explorer 5000 Plus + Battery Pack 5000 Plus 10,080 Wh 7,200 W 14,400 W Planning runtime 115.0 hours. Published capacity meets this duration on these assumptions. That is not a guarantee the appliance will run. preorder See preorder details at Jackery (opens in a new tab)
EcoFlow RIVER 2 Pro 768 Wh 800 W 1,600 W Shortfall: 1,336.4 Wh below the planning minimum. Planning runtime 8.8 hours. in stock Check price at EcoFlow (opens in a new tab)
EcoFlow DELTA 3 Classic 1,024 Wh 1,800 W 3,600 W Shortfall: 1,080.4 Wh below the planning minimum. Planning runtime 11.7 hours. in stock Check price at EcoFlow (opens in a new tab)
EcoFlow DELTA 3 Plus 1,024 Wh 1,800 W 3,600 W Shortfall: 1,080.4 Wh below the planning minimum. Planning runtime 11.7 hours. preorder See preorder details at EcoFlow (opens in a new tab)
Jackery Explorer 1500 v2 1,536 Wh 2,000 W 4,000 W Shortfall: 568.4 Wh below the planning minimum. Planning runtime 17.5 hours. in stock Check price at Jackery (opens in a new tab)
Jackery Explorer 2000 v2 2,042 Wh 2,200 W 4,400 W Shortfall: 62.4 Wh below the planning minimum. Planning runtime 23.3 hours. preorder See preorder details at Jackery (opens in a new tab)
EcoFlow DELTA 3 Max 2,048 Wh 2,400 W 4,800 W Shortfall: 56.4 Wh below the planning minimum. Planning runtime 23.4 hours. in stock Check price at EcoFlow (opens in a new tab)
EcoFlow DELTA 3 Max Plus 2,048 Wh 3,000 W 6,000 W Shortfall: 56.4 Wh below the planning minimum. Planning runtime 23.4 hours. preorder See preorder details at EcoFlow (opens in a new tab)
EcoFlow DELTA 3 Plus + DELTA 3 Series Extra Battery 2,048 Wh 1,800 W 3,600 W Shortfall: 56.4 Wh below the planning minimum. Planning runtime 23.4 hours. preorder See preorder details at EcoFlow (opens in a new tab)

Find a battery for your fridge

Choose the refrigerator or freezer and how long it should run. A yellow-label kWh figure is optional.

Step 1

What kind of fridge?

Step 2. How long should it last?
Other durations

Leave blank to use the style estimate. Greater than 0 and at most 20,000. This is yearly energy, not running watts. If you also enter measured watts, the measurement is used.

Leave blank unless a meter measured the average. Greater than 0 and at most 5,000. A day-long average is not the compressor's running watts.

Advanced

Leave blank for one appliance. If you fill it in, both averages are added and the 10 W idle allowance is counted once. Two separate power stations would each have their own idle use.

This plans a bit higher. It is an assumption, not a measurement of your fridge.

Where should the energy number come from?

Not sure uses full-size refrigerator-freezers. French door is counted with bottom freezers, because ENERGY STAR does not list it separately.

Optional. Not sure keeps the wider list. A size is used only when that volume group has at least 30 certified rows. The 18 and 22 cubic foot cuts are KeepCold groups, not an official class.

Optional. Brand does not change the estimate. This is not a model lookup. If you have the yellow label, use “I know the energy use.” What to copy from EnergyGuide.

Leave this blank if you do not know. Startup compatibility stays unconfirmed, and surge ratings are not compared.

Planning assumptions (efficiency 0.85, reserve 10 percent, idle 10 W)

0.85 means 85 percent. Must be greater than 0 and at most 1.

10 means keep 10 percent unused (a reserve fraction of 0.10). It must be under 100.

Added to average watts before efficiency. Default 10 W. It is not a second, hidden loss.

Choose Calculate. You don’t need watts for a first estimate.

What the inputs mean

Annual kilowatt-hours become average watts by multiplying by 1,000 and dividing by 8,760, the hours in a non-leap year. A measured average is used as-is. Running watts times a duty-cycle fraction is another average. All three describe energy over time, not the brief startup spike.

Continuous watts on a power station are the output it is published to hold. Surge watts are a short published peak. Compare those ratings only to a startup figure you actually know. If you do not know it, this page will not pretend the comparison happened.

Efficiency, reserve, idle, age, and temperature move the real result. A cold garage, an old battery, or a refrigerator that runs more because the kitchen is hot can use the reserve you set aside. The defaults are planning choices: efficiency 0.85, reserve 0.10, and a 10 W idle allowance added to average watts before that efficiency is applied.

Read the full method, the watts explainer, and the EnergyGuide page before treating a result as a shopping decision.

Common questions

Does matching the watt-hours mean my refrigerator will run?

No. The number is a planning estimate. Check the fridge temperature with a thermometer.

What if I do not know startup watts?

Leave it blank. You’ll still get a battery-size estimate. We just won’t compare the startup spike.

Where does the 10 W idle go in the formula?

It is an AC-equivalent allowance added to average watts before inverter efficiency. Runtime is capacity × 0.85 × 0.90 ÷ (average watts + 10). There is no second, hidden derating.

These are estimates. Real runtime depends on your fridge, its age, and how often it's opened.