What each generator size runs
The size here is the generator's running watts. Under the 80% rule, the load you run for hours should stay at or under 80% of that. The generator's starting watts must also cover the peak, which is your running load plus the single biggest motor start.
On a small screen, scroll the table sideways to read every column.
| Running watts | Load to plan for (80%) | Example list that fits | That list adds up to | Good for |
|---|---|---|---|---|
| 5,000 W | 4,000 W | Fridge, freezer, LED lights, Wi-Fi, phone charging, a CPAP, a sump pump, a furnace fan, a well pump and a microwave | 3,945 W running, 5,045 W peak | Outage essentials with a well and a furnace fan |
| 7,500 W | 6,000 W | The 5,000 W list plus a small window AC and a coffee maker | 5,545 W running, 6,745 W peak | Essentials plus some comfort in one room |
| 10,000 W | 8,000 W | The 5,000 W list plus a space heater, an electric kettle and a small window AC | 7,245 W running, 8,445 W peak | A more comfortable outage, with heat or cooling in a room or two |
| 13,000 W | 10,400 W | The 10,000 W list plus a coffee maker and a TV | 8,365 W running, 9,565 W peak | Most everyday loads at once, short of central air or an electric range |
How these were worked out
Each list uses the typical running and starting watts from our household wattage chart. The running total is the sum of everything running at once. The peak adds only the biggest single starting kick, because motors rarely start at the same moment. Start the biggest motor first, then switch the rest on one at a time.
Check the running number on the generator label, not just the name. Some generators are named for their starting watts, so a “5,000 W” model may run less than 5,000 W.
Central air and whole-house power
Central air, an electric range, an electric water heater or an electric dryer each add thousands of watts, and some run on 240 V. Once those are on the list you are usually looking at a home standby generator, sized and installed by a licensed electrician. To power circuits in the house instead of running extension cords, you need a transfer switch or interlock fitted by an electrician. Never plug a generator into a wall outlet.
Questions
Is 6,000 watts enough to run a house?
For the outage essentials, a furnace fan, a well pump and a microwave, yes: that list is 3,945 W running and 5,045 W at peak, so a generator that runs 6,000 W covers it if it starts at least 5,100 W. It will not run central air or an electric range as well.
Will a 13,000 watt generator run a whole house?
It runs most everyday loads at once, such as the essentials plus a space heater, a kettle, a small window AC, a coffee maker and a TV at 8,365 W running. Central air, an electric range, a dryer or an electric water heater usually need a home standby generator sized by an electrician.
What is the 80% rule for generators?
Keep the load you run for hours at or under about 80% of the generator's running watts. A generator that runs 10,000 W should carry about 8,000 W or less for long runs.