The question is really four questions
"How many watts to run a house" has no single answer because the phrase covers everything from keeping food cold to living as if nothing happened. Separate them and the numbers become obvious.
| Tier | What runs | Running watts | Peak watts |
|---|
| 1 — Survive | Fridge, lights, router, phones | ~300 | ~1,200 |
|---|
| 2 — Critical circuits | Above, plus freezer, furnace blower, well or sump pump | ~1,500-2,500 | ~4,000-5,000 |
|---|
| 3 — Comfortable | Above, plus a window AC or one range element | ~3,500-5,000 | ~7,000-8,000 |
|---|
| 4 — As if nothing happened | Above, plus central AC, electric water heating, dryer | ~10,000-15,000 | ~15,000-20,000+ |
|---|
Built up from Champion Power Equipment's and Honda Power Equipment's published appliance figures plus this site's stated 150W fridge planning average. Peak columns apply the largest-single-surge method rather than adding every starting figure together. These are planning brackets, not a survey of houses — yours will differ, and the wattage chart has the underlying numbers.
Almost everyone who says "run the house" means tier 2. Almost everyone who prices tier 4 stops and reconsiders.
What makes tier 4 so expensive
Three loads, and they are all the same kind of thing: appliances that move or make heat with electricity directly.
- Central air conditioning. Champion publishes 3,000-3,500 running and 5,000-6,000 starting for a 3 ton unit. That one appliance is larger than tiers 1 and 2 combined.
- Electric water heating. 3,000-4,500W whenever it cycles, and it cycles on its own schedule.
- Electric range, oven and dryer. Thousands of watts each, and a range with several elements on is a house-sized load by itself.
Which points to the most useful strategy in the whole category: if your heating, cooking and hot water run on gas, backup power gets dramatically cheaper. A gas furnace needs only its blower, a gas water heater often needs nothing at all, and a gas range can usually be lit by hand.
Why nobody powers the whole panel
A typical modern house has a 200 amp service, which at 240 volts is a theoretical 48,000 watts. No portable generator comes close, and no household ever draws it — service size is about the maximum a house could ever demand, not what it uses.
The point of a transfer switch is precisely that you choose a handful of circuits in advance and power those. Ten circuits is the common residential kit size, and ten well-chosen circuits covers tier 2 comfortably.
Choosing them is the useful exercise: the connection guide walks through which circuits earn a slot.
Watts is only half of it
A generator sized correctly in watts can still be the wrong purchase, because watts say nothing about how long you can keep them coming.
At 0.32 gal/hr, six hours a day of a 5,300W machine is about 1.9 gallons — so three days is under six gallons, which is two cans in the garage. The same three days run continuously is about 23 gallons, which is more than many jurisdictions permit in an attached garage.
Block running is what makes the fuel arithmetic work, and it costs nothing: six hours a day keeps a fridge and freezer safe indefinitely. The consumption arithmetic and the storage limits cover both sides.
Where a battery lands on this scale
Portable batteries cover tier 1 outright and reach into tier 2 with load shedding. They do not reach tier 3 or 4, and no amount of capacity changes that — a 1,500W space heater or a 3,500W air conditioner would empty any of them in an hour.
What a battery does uniquely well is run tier 1 indoors, silently, all night. Which is why the arrangement we would actually recommend for a long outage is a generator at tier 2 running in blocks during the day, and a battery covering the essentials overnight.
Generator versus power station makes the case, and sizing a battery works the other half.
How to get your own number in ten minutes
- Write down what has to keep running. Be honest — the list is usually shorter than the first draft.
- Look each item up in the wattage chart, or read the label on the appliance itself.
- Add the running watts.
- Find the largest single starting wattage and add the difference between it and that appliance's running figure. Why you do not add them all.
- Add 20% margin. Labels are optimistic and old appliances draw more than new ones.
- Buy the machine whose running watts exceed that figure — not the one whose peak watts do.
That last step is the one that catches people. A generator advertised as "9,500 watts" may be 9,500 peak and 7,500 running. The running number is what you own.
