How Many Watts to Run a House During an Outage?

Type this question into Google and you get numbers between 3,000 and 12,000 watts. All of them are technically right and all of them are answering a question you didn't ask.

Because you are not trying to run a house. You're trying to keep four things alive in one.

Those are very different numbers.

The two questions people confuse

"How many watts to run my house normally?" — 5,000 to 7,500 watts for a typical US home, more with electric heat or an electric range. verify That's a standby generator conversation.

"How many watts to get through an outage?" — about 400.

Here's how that second number is built.

Adding it up honestly

verify on each of those.

That's the entire outage for most households. Three hundred and fifty watts.

The number that actually matters

Running watts is the easy part. Startup surge is what trips units.

Anything with a motor spikes hard for under a second when it kicks on:

• Fridge: ~150W running, ~900W spike verify
• Sump pump: ~600W running, ~1,800W spike verify
• Well pump: ~800W running, ~2,500W spike verify
• Window AC 8,000 BTU: ~750W running, ~2,200W spike verify

If your inverter can't supply that instant, it shuts off. Full battery, doesn't matter.

So the real shopping rule is: find your biggest spike, then buy something that clears it comfortably. Capacity is the second question, not the first.

What each size actually covers

1,800W output — fridge, internet, lights, fans, phones, a TV. Covers the 350W list with a lot of headroom for the fridge spike. This is where most people should be.

2,400W output — the above plus a small window AC for a couple of hours, or several things running simultaneously without thinking.

4,000W and 240V — well pump, some dryers, actual circuits. Needs a transfer switch and an electrician.

5,000W+ — you're buying a generator now, not a battery.

The things that break the budget

Four appliances account for almost all the difference between a $700 answer and a $4,000 one:

Electric heat. A 1,500W space heater eats a kilowatt-hour every forty minutes. Nothing portable solves this. If you have gas heat, powering just the furnace blower — around 400W — warms the whole house instead.

Air conditioning. A window unit is hours, not nights. Central air isn't a conversation.

Well pump. 240V and a huge spike. Different product category entirely.

Electric range or water heater. Don't. Use a camp stove and accept cold showers for two days.

Doing it for your own house

Go look at the label on the back of each appliance you actually care about.

If it lists watts, that's your number. If it lists amps, multiply by 120.

Then remember duty cycle — anything with a compressor or a thermostat cycles on and off. A fridge labelled 150W runs about a third of the time, so its daily energy use is far lower than 150 × 24. Missing this is the most expensive mistake in this whole category.

A Kill A Watt meter costs about as much as a pizza and gives you the real numbers for your actual appliances. If you're about to spend a thousand dollars, spending twenty to be sure is easy arithmetic.

Straight answer

About 400 watts runs what matters in a normal house during a normal outage.

Buy a unit with at least 1,800W output so the fridge spike never troubles it, and pick your capacity based on how many hours you need.

Anyone quoting you 7,500 watts is answering the question "how do I run my house as if nothing happened." That's a different product, a different budget, and for most people, a different problem entirely.