The number you actually need is not on the label
A refrigerator's nameplate states the power it draws while the compressor is running. It says nothing about how often that is.
In practice a modern fridge cycles — the compressor runs until the cabinet reaches temperature, then stops until it drifts back up. Across a day, the compressor is running perhaps a third of the time.
Which produces the two numbers that matter, and they are different by a factor of several:
- Compressor running draw — what the label says, and what your inverter has to sustain while it runs.
- Average draw across the day — running draw multiplied by duty cycle, and the figure that decides your watt-hours.
This site uses 150W as the average fridge draw, stated as a planning assumption on the methodology page, and every runtime figure on the site is calculated from it.
Three numbers, and what each is for
| Figure | Typical value | What it decides |
|---|
| Starting watts | 500-1,000 W | Whether your inverter or generator can start it at all |
|---|
| Running watts, compressor on | 100-500 W | What has to be sustained while it cycles |
|---|
| Average across 24 hours | ~150 W | How many watt-hours a day it consumes |
|---|
Starting and running figures are Champion Power Equipment's published ranges for refrigerators and freezers. The 150W average is this site's stated planning assumption rather than a manufacturer figure — we have not metered any appliance, and yours will differ.
150W across 24 hours is 3,600Wh a day. Divide by 85% inverter efficiency and a battery needs about 4,200Wh to run a fridge continuously for a day — which is more than any portable unit on this site holds.
That number is not a mistake, and it is why the next section is the most useful thing on the page.
Block running changes everything
A refrigerator is a thermal store. Powered down, a closed fridge holds temperature for hours — USDA guidance is about four hours for a refrigerator and 48 for a full freezer.
So you do not have to run it continuously. Power it long enough to pull the cabinet down to temperature, switch it off, and let it coast.
| Pattern | Daily energy | From a 1kWh battery |
|---|
| Continuous, 24 h | ~3,600 Wh | About 6 hours |
|---|
| 12 hours on, 12 off | ~1,800 Wh | About half a day of coverage |
|---|
| 4 hours in 12, twice a day | ~1,200 Wh | Most of a day, and food stays safe |
|---|
Calculated from the 150W average with 85% inverter efficiency. The marked row is the pattern we would actually use — it cuts consumption by two thirds and keeps the cabinet comfortably inside the USDA guidance provided the door stays shut between runs.
The discipline that makes it work is simple: keep the door shut. Every opening dumps the cold air you just paid for.
What makes one fridge draw more than another
- Age. The single biggest factor. Efficiency standards have tightened repeatedly, and a fifteen-year-old unit can use substantially more than a current one of the same size.
- Ambient temperature. A fridge in a hot garage works far harder than the same unit in a cool kitchen, because it is moving heat against a bigger gradient.
- Door seals. A perished gasket means the compressor runs more. Test with a sheet of paper — if it pulls out easily with the door closed, the seal is gone.
- Condenser coils. Dusty coils shed heat badly and raise the duty cycle. Cleaning them is fifteen minutes.
- How full it is. A full fridge has more thermal mass and holds temperature better between compressor runs.
- Ice makers and through-door dispensers. Both add real consumption, and both are worth switching off during an outage.
Finding your own number
The 150W planning average is a reasonable default. Your actual figure is knowable and it takes no equipment:
- Find the annual kWh figure on the energy label, which most fridges sold in the last two decades carry.
- Divide by 365 for kilowatt-hours a day.
- Divide by 24 and multiply by 1,000 for the average draw in watts.
A fridge rated at 400 kWh a year works out to about 1.1 kWh a day, or roughly a 46W average — considerably better than the planning figure, and a good illustration of how much modern efficiency standards have achieved.
Treat that as a floor rather than a promise: label figures come from a standardized test, and a real fridge in a real kitchen with a real door being opened does worse. How to read a nameplate covers what the various numbers on an appliance actually mean.
Sizing equipment around it
For a refrigerator specifically:
- Inverter output of at least 1,800W. The 500-1,000W starting surge needs margin, and a compressor restarting against pressure draws hardest of all.
- Capacity from your intended run pattern, not from 24 hours. Block running is the realistic plan.
- Add the freezer separately if you have one — two compressors is a different surge problem.
- Anything with a compressor is a poor fit for a small UPS. A 300W station will not start it however many watt-hours it holds.
The full sizing method works both numbers through, and the refrigerator roundup covers the products.
