How Long Will a 1000Wh Power Station Run a Fridge?

Where the wrong answer comes from

Almost everyone does this sum:

1,000Wh ÷ 150W = 6.7 hours

That number is wrong, and it is wrong in your favour, which is unusual for spec-sheet arithmetic.

It assumes the compressor never stops. In reality a fridge pulls its full draw only while actively cooling. Once it reaches temperature it switches off and coasts, and it only wakes when the interior drifts a degree or two — or when you open the door.

That proportion is the duty cycle, and for a fridge with the door mostly shut it lands around one third. verify

150W × 0.33 duty cycle = ~50W average

1,000Wh ÷ 50W = ~20 hours

By fridge type

Not all fridges are the 150W example.

verify on every figure in this table — these are typical mid-range US appliances, not your specific one.

Two things skew this. Icemakers and through-door dispensers add load that has nothing to do with keeping food cold, and they are worth switching off during an outage. Age matters too: a fridge from 2005 draws substantially more than a similar one built to current standards.

Your own fridge has a label inside the door or on the back with its real figures. That number beats any table on the internet, including this one.

Run the numbers for your actual setup

A fridge is rarely the only thing you want running. Tick what matters and get a real figure rather than a category average:

What else fits alongside the fridge

The useful question is not usually "fridge only." It is "fridge and what else, for how long."

The pattern that shows up every time: the fridge is the expensive item and everything else is nearly free by comparison. Your router, a few LED lamps and phone charging together draw less than the fridge does on its own.

That is why a 1kWh unit covers most of what an outage takes from a household. It is not that 1,000Wh is a lot. It is that lights and internet cost almost nothing, and the fridge is the whole problem.

Capacity is not what decides whether it starts

Worth separating clearly, because it is the mistake that costs people money.

Watt-hours decide how long. Watts decide whether at all.

A fridge compressor spikes to roughly 900W for under a second when it kicks on. verify If your inverter cannot supply that instant, the fridge does not run slowly — the unit trips and shuts off, usually at 3am.

So a 1,000Wh unit with an 1,800W inverter runs a fridge all night without complaint. A 1,000Wh unit with a 600W inverter will not start it once.

If yours is tripping, we wrote up why — and the fix is surge headroom, never a bigger battery with the same inverter.

How to stretch it a long way

Four things that genuinely change the number, in order of effect.

Cycle it rather than running it continuously. A fridge does not need constant power — it needs to be brought back down to temperature periodically. An hour on and three hours off keeps food safely cold and uses far less energy. The food does not notice. This is the biggest single lever you have, and it is free.

Keep the door shut. Obvious, and still the thing people get wrong. Every opening costs you cold air you then pay to replace.

Fill the empty space. A full fridge holds temperature much longer than an empty one because the contents themselves store cold. Water bottles in the gaps work fine and cost nothing.

Turn off the icemaker. It is a heater and a motor working against the thing you are trying to power.

More of this in keeping food cold in an outage, including how long the food is actually safe with no power at all — which is longer than most people assume and worth knowing before you spend anything.

Is 1,000Wh the right size for you?

For most US households, yes — and not because it is generous.

Most US outages end within a day. A 1kWh LiFePO4 unit with a decent inverter covers a fridge, the internet, lights and phones for that long, which is essentially the whole problem for a one-night event.

Where 1,000Wh is not enough: hurricane and ice-storm regions where multi-day outages are normal, homes on a well pump, and anyone running medical equipment who needs a real margin rather than an estimate. At three days the question stops being battery size and becomes recharging — which means solar panels or a car adapter.

Where it is more than you need: if your honest worry is phones, a router and a lamp through a two-hour outage, a 300Wh unit does that and costs a fraction as much.

Size it against your actual outage, not the worst one you can imagine. The calculator walks through it properly, and our outage picks name who each unit is wrong for as well as who it suits.

The short version

About 20 hours for a normal fridge, roughly double what the naive sum predicts, because compressors rest and the label figure assumes they never do.

Shut the door, cycle it if the outage runs long, and check your inverter's surge rating rather than its watt-hours if the fridge is tripping it.