Quick answer: Generator size for a fridge and freezer comes to 575 W running on the two loads anybody publishes — a fridge and a gas furnace blower — not the 4,500 the first page of results adds up to. The gap is one number: those pages cost a gas furnace as if it were an electric heater.
This is the most common three-load question in home backup, and the answers to it cluster around a 6,000 to 8,000 W generator. That recommendation rests on a figure that is not wrong by a margin but wrong by a category. Our generator sizing guide sets out the method; this page applies it to the three appliances people actually ask about.
The short version
| Load | What the first page of results says | What a primary source publishes |
|---|---|---|
| Refrigerator | 600–800 W | 105–158 W with the compressor running |
| Gas furnace | 3,500–5,000 W | 27–499 W for the blower, plus under 80 VA for the inducer |
| Chest freezer | 400–800 W | nobody publishes one; the certified average is 23–39 W |
| Total | 4,500–6,600 W, so buy 6,000–8,000 | 575 W for the two that are published, 655 with the inducer |
The furnace figure is a category error
Three thousand five hundred watts is a real number for a heating appliance. It is the number for electric resistance heat — a baseboard, a wall heater, the strips in an air handler. It is not a gas furnace.
A gas furnace burns gas. The gas does the heating. What it needs from a generator is the electricity to move air and light the burner, and that is four small things: the blower motor, the combustion inducer, the hot surface igniter and the control board. Trane publishes 27 to 499 W for one blower across its whole speed and duct-pressure range, and rates the inducer at 0.66 A at 120 V, which is under 80 VA. The igniter pulls hard for a few seconds at each start. The board is negligible.
Put the blower at its highest published figure, add the inducer, and the whole furnace is under 500 W. The recommendation you are being given is seven to ten times that, and the extra is a heater that is not in your house.
If you do have electric resistance heat, the first-page figure is closer to right and nothing else on this page will save you: resistive heat is the one job a portable generator does badly, and it is the reason sizing from the wrong number gets expensive so fast.
One of the three has no published number at all
We went through every chest freezer holding current certification when we worked out what a chest freezer draws. There are nine of them. Not one publishes what its compressor pulls while it is running.
What the certification gives you is annual kilowatt-hours, and dividing that out gives an average of 23 to 39 W across the whole year. That average is the right number for sizing a battery, because a battery is buying energy. It is the wrong number for a generator, which has to carry the load in the moment the compressor is actually on — and the compressor is off most of the time.
So we are not going to give you a total for all three. Anyone who does is filling that hole with a guess. The plate inside the lid gives amps and volts, and multiplying them gives a ceiling rather than a draw — the trap we took apart in how to read an appliance label, where the same shortcut overstated a well pump by 72 per cent.
The 48 hours that change the question
Before you size anything, the premise is worth testing. The USDA publishes how long each appliance holds without power at all, on one condition: the doors stay shut.
| Appliance | How long it holds, doors closed |
|---|---|
| Freezer, full | about 48 hours |
| Freezer, half full | about 24 hours |
| Refrigerator | 4 hours |
Read that against the question. For the first two days of an outage a full freezer needs nothing, and the correct action is to leave it shut. The fridge is the one on a four-hour clock. So the honest version of “all three at once” is usually two: the fridge and the furnace, with the freezer sitting there doing its job unplugged.
That is not a sizing trick, it is what the food safety agency tells you to do anyway. It happens to remove the one load nobody can put a number on. If the outage runs past two days, the freezer joins the list — and by then you have watched the generator handle the other two and you know what headroom you have — and what that headroom costs in fuel per hour.
What actually decides the size
Not the sum. The rule, which Generac prints in its own manual and we quoted in the sizing guide, is the starting watts of the single largest motor plus the running watts of everything else. Motors do not start together.
Among these appliances the largest single starting event is the fridge. Certification data records a compressor inrush reaching 4,626 VA. That is a sub-cycle peak lasting milliseconds rather than a motor spinning up, no maker publishes how an alternator responds to something that short, and it is not what the industry sizes on — but it is the largest published figure in the set and pretending otherwise would be dishonest.
What this means in practice is that the running total is not your constraint. At 575 W you are nowhere near the limit of even the smallest useful machine. The constraint is whether the unit tolerates a compressor start, and that is a surge specification, not a wattage sum.
Generator size for a fridge and freezer, by case
Gas furnace, fridge, freezer left shut
Two loads, 575 W running, one compressor start to absorb. This is the common case and it does not need a large machine. Buy for the surge rating and for how quiet it is, because you will be listening to it.
An outage past two days
The freezer joins in, and its running figure is the one nobody publishes. Read the plate, treat volts times amps as a ceiling, and note that you now have two compressors that can start independently. This is where a little headroom earns its keep.
Electric heat rather than gas
Different question and a much worse one. A resistance heater does not have a small electrical share of a gas-fired job; the whole heat output is the electrical load. Nothing on this page transfers, and the first-page numbers you were reading are closer to your reality than to anyone else’s.
How we read this
Every figure in the right-hand column is quoted from the article linked beside it, and each of those traces to a certification database or a manufacturer specification sheet with the date it was read. The hold times are the USDA’s. The left-hand column summarises what the first page of results for this question recommends, read on 8 September 2026.
One sum is ours: 158 W plus 417 W is 575, and adding the inducer gives 655. We are deliberately not giving a three-appliance total, because the freezer’s running draw is not published by any of the nine certified models and we are not going to estimate it and then present the estimate as a figure. No generator was tested and none is recommended. Our method is at how we test.
The furnace is the dangerous one here
A gas furnace vents combustion gases. Do not improvise a connection to it, do not open the cabinet to read a label with the power on, and do not run it with any part of its venting disturbed. Feeding a furnace from a generator is a transfer switch job for a qualified electrician, and it is the same rule as everywhere on this site: never run a generator into a wall socket to power the house. That is backfeeding and it can kill a utility worker.
The generator itself lives outside, well away from windows, doors and vents, never in a garage even with the door open. Carbon monoxide from a portable generator kills quickly and without warning. Fit a battery-operated CO alarm indoors.
Frequently asked questions
Will a 2,000 W generator run a fridge and a furnace?
On running watts, comfortably: the two together are about 575 W on published figures. Whether a particular 2,000 W unit absorbs the fridge’s compressor start is a question about its surge rating, which is printed on its own specification sheet and is the number to check.
Why do other sites say I need 6,000 watts?
Because they cost the furnace at 3,500 to 5,000 W, which is electric resistance heat rather than a gas furnace. Correct that one line and the total falls by roughly nine tenths. The refrigerator figures they use are also several times the certified ones.
How many watts does a chest freezer use?
Averaged over a year, 23 to 39 W. While the compressor is actually running, nobody publishes it: none of the nine certified models gives a figure. The plate inside the lid gives amps and volts, and their product is a ceiling rather than a draw.
Do I need to run the freezer at all?
For the first 48 hours, if it is full and you keep it shut, the USDA says no. Half full, 24 hours. The refrigerator is the one with a four-hour limit, so if you are only powering one of the two, power that.
Does a gas furnace really need so little?
The gas does the heating; the electricity only moves air and lights the burner. Trane publishes 27 to 499 W for a blower across its full range and 0.66 A for the inducer. Add the igniter and the board and a whole furnace stays under 500 W.
Check whether your heating is gas or electric before you read another wattage chart, because that single fact moves the answer by a factor of ten. Then leave the freezer shut, size for the fridge’s compressor start rather than for a sum, and treat any page that hands you a confident three-appliance total as a page that has guessed at the one number nobody prints.
This article is general information, not an installation guide and not a substitute for a licensed electrician. Electrical work on a service panel, a transfer switch or a utility connection is regulated in most jurisdictions and normally requires a permit and an inspection. Fuel-burning equipment produces carbon monoxide and must never be run indoors, in a garage or near an opening into the home.
