How Long Will a Power Station Run a Fridge? The Math, Not a Guess
Fridges cycle on and off, which is why brand runtime claims are useless. Here's how to work out your own number from the label on your fridge — and which capacity class it puts you in.
“How long will it run a fridge” is the most-asked question in this category and the one manufacturers answer worst. You’ll see “runs your refrigerator for 20 hours!” on a box, with no mention of which fridge, which duty cycle, or whether that figure came from a household unit or a camping cooler. The two differ by a factor of four.
The good news is that this is arithmetic, not opinion. Give me the label on your fridge and five minutes and you’ll have a number you can trust — and the same method works whether you’re sizing a portable power station for weekend camping or a solar generator for a multi-day outage.
The short answer
For a typical 18 cu ft household refrigerator using about 1.2 kWh per day, and a power station’s usable energy after inverter losses:
| Power station class | Usable AC energy | Household fridge (48 W avg) | 12V camping fridge (13.5 W avg) |
|---|---|---|---|
| 500 Wh | 425 Wh | 9 hrs | 31 hrs |
| 1,000 Wh | 850 Wh | 18 hrs | 63 hrs |
| 2,000 Wh | 1,700 Wh | 35 hrs | 126 hrs |
| 3,600 Wh | 3,060 Wh | 64 hrs | 227 hrs |
Usable energy is rated capacity × 0.85 for inverter losses. The average draws are derived in the next two sections — they are not nameplate wattages.
Those are the numbers most people need. If your situation is ordinary, stop here and go to the sizing calculator. If you want to know where they come from — or your fridge isn’t typical — keep reading.
Why the nameplate wattage misleads you
A refrigerator’s compressor doesn’t run continuously. It runs until the compartment hits temperature, shuts off, and waits. The fraction of time it spends running is the duty cycle, and for a healthy fridge in a normal room it lands somewhere between 30% and 50%.
That means the wattage on the label — the compressor’s draw while running — overstates real consumption by roughly half:
| Running draw | Duty cycle | Average draw | Per day | |
|---|---|---|---|---|
| Household fridge (18 cu ft) | 120 W | 40% | 48 W | 1,152 Wh |
| Compact / dorm fridge | 80 W | 35% | 28 W | 672 Wh |
| 12V portable (camping) | 45 W | 30% | 13.5 W | 324 Wh |
Size from the average, never the running draw. Sizing from 120 W would tell you a 1,000 Wh battery lasts 8 hours when it actually lasts 17 — you’d buy twice the battery you need.
Getting your fridge’s real number
Three ways, in order of accuracy.
1. The energy guide label (best). Every fridge sold in the US carries a yellow EnergyGuide sticker with an estimated annual consumption in kWh. Divide by 365:
420 kWh/year ÷ 365 = 1.15 kWh/day = 1,150 Wh/dayThis is the most reliable figure you can get without instrumenting anything, because it already accounts for the duty cycle. Use it if you have it.
2. A plug-in energy meter (better still, but takes a day). A $20 meter left on the fridge for 24 hours gives you your actual consumption in your actual kitchen — which matters, because a fridge in a 90°F garage can use half again as much as the same unit in an air-conditioned kitchen.
3. Estimate from the running watts. If you only have the nameplate, multiply by 24 hours and by a 0.4 duty cycle:
120 W × 24 h × 0.4 = 1,152 Wh/dayRound up. A fridge that’s opened frequently, is packed full of warm groceries, or sits in a hot room will exceed this.
Then subtract the inverter’s cut
A power station stores DC and your fridge wants AC, so an inverter sits in between and takes a cut. Typical AC inverter efficiency in this class runs 85–90%. We use 85% throughout this site — including in the calculator — because it’s the conservative end and because efficiency sags at very low loads, which is exactly where a cycling fridge spends most of its time.
So the formula in full:
runtime (hours) = (capacity_Wh × 0.85) ÷ average_draw_WWorked for a 1,000 Wh station and the household fridge above:
1,000 Wh × 0.85 = 850 Wh usable
1,152 Wh/day ÷ 24 h = 48 W average
850 ÷ 48 = 17.7 hoursJust under eighteen hours — not the 7 you’d get by sizing off the 120 W nameplate, and not the 20+ the box promises.
The one place the surge does matter
None of the above touches the startup surge. When a compressor motor kicks in, it draws three to seven times its running wattage for a fraction of a second. A fridge that runs at 120 W can spike past 800 W.
That surge doesn’t meaningfully affect your battery capacity — it’s over in milliseconds. What it affects is whether the inverter trips. Two rules:
- Continuous rating must exceed the fridge’s running watts, with margin.
- Surge rating must exceed the startup spike, which you should assume is 5× running watts unless the manufacturer publishes an LRA figure.
For the 120 W household fridge that means at least 600 W of surge headroom. Every unit in our database clears that comfortably — a 300 W-class unit like the EcoFlow RIVER 2 has 600 W of surge — but a very small power bank or a cheap modified-sine inverter may not. If a fridge trips your inverter on start-up while running fine afterwards, this is why.
What this means by use case
Weekend camping with a 12V fridge
A 12V compressor fridge (the Dometic/ARB type) is the efficient case: roughly 300–400 Wh per day. A 1,000 Wh station covers a two-night trip with room for phones and lights. Add a 100 W panel and you can stay out indefinitely in decent sun.
This is why the camping recommendation lands where it does — see the camping guide for the picks.
A household fridge through an outage
Budget 1.2–1.5 kWh per day. That reframes the question: a single overnight outage is easy, and almost any 1,000 Wh unit handles it. A three-day outage is 4.5 kWh, which no portable unit does on battery alone — you need either the expandable 3,000 Wh+ class or solar input to top up during the day.
The honest answer for multi-day outage planning is that a power station keeps your food cold and your phones charged; it is not a whole-house generator substitute unless you go to the 3.6 kWh-and-expandable class.
A garage or second fridge
Add 30–50% to your estimate. Ambient temperature drives fridge consumption hard, and an uninsulated garage in summer is the worst case most people actually encounter.
Matching the number to a capacity class
Once you have daily watt-hours, the capacity class follows:
| Daily fridge load | Runs 24 hrs on | Runs 48 hrs on |
|---|---|---|
| 300 Wh (12V camping) | 500 Wh class | 1,000 Wh class |
| 700 Wh (compact) | 1,000 Wh class | 2,000 Wh class |
| 1,200 Wh (household) | 2,000 Wh class | 3,000 Wh+ class |
| 1,800 Wh (garage/hot) | 3,000 Wh class | 3,000 Wh+ with solar |
Remember these are for the fridge alone. Real outages also involve phones, lights, a router, and possibly a CPAP — add those loads before you choose. The calculator does that part for you and shows the arithmetic as it goes.
Three ways to stretch the number
Don’t open it. A closed fridge holds temperature for hours. Every opening dumps cold air and forces a compressor cycle. During an outage, decide what you want before you open the door.
Let it cycle wider. Some 12V fridges let you raise the setpoint a few degrees. Going from 34°F to 40°F is still food-safe and can cut consumption noticeably, because the compressor runs less often.
Use DC where you can. A 12V fridge run from the power station’s DC output skips the inverter entirely — that’s the 15% back, immediately. If your unit has a 12V socket and your fridge came with a 12V cable, use it. This is the single biggest efficiency win available and most people never take it.
What we’d tell a friend
Get the EnergyGuide number if you can. Multiply your daily watt-hours by the number of days you need to cover, divide by 0.85, and buy the next capacity class up from whatever that lands on. Then, if the fridge is the reason you’re buying, check the surge rating rather than assuming it’s fine.
And treat any “runs a fridge for X hours” claim on a box as marketing until you know which fridge they meant.
Frequently asked questions
- How long will a 1000Wh power station run a refrigerator?
- A 1,000 Wh power station delivers roughly 850 Wh of usable AC energy after inverter losses. A typical 18 cu ft household fridge averages 48 W once you account for its duty cycle, so 850 ÷ 48 gives about 18 hours. A 12V portable camping fridge averages around 13.5 W and runs roughly 63 hours from the same battery.
- Do I need to account for the fridge's startup surge?
- Yes, but for the inverter rating rather than the capacity. A compressor draws three to seven times its running wattage for a fraction of a second at start-up. A fridge that runs at 120 W can spike past 800 W, so you need an inverter with enough surge headroom — capacity in watt-hours is unaffected.
- Why is the fridge's wattage rating so much higher than what it actually uses?
- The label states the compressor's draw while running, but a fridge compressor only runs 30–50% of the time. A 120 W fridge at a 40% duty cycle averages 48 W, which is why you must size from daily kWh, not from the nameplate wattage.
- Can a power station run a fridge overnight during an outage?
- Almost any 1,000 Wh or larger unit will run a household fridge overnight. The harder question is a multi-day outage — that needs roughly 1.5 kWh per fridge per day, so a two-day outage points at the 3,000 Wh class or a smaller unit paired with solar.