A 7,500-watt generator can run most of a home’s essentials during an outage: the refrigerator and freezer, furnace fan, well pump, sump pump, lights, TV, computer and microwave, with room to rotate in a window AC or space heater. It usually can’t run central air conditioning, and big electric loads like a water heater or dryer only work if you turn most other things off. To power hardwired items like a furnace or well pump, you need a transfer switch or interlock, not extension cords.
Running watts vs. starting watts
Generators list two numbers. Running (rated) watts are what it can supply all the time. Starting (surge) watts are the extra it can supply for a few seconds when a motor starts. Many generators sold as “7,500 watts” are rated around 7,500 running watts with 9,000 or more starting watts, but some use the higher number in the name. Check the spec sheet.
Motors and compressors, like pumps, refrigerators and air conditioners, need about three times their running watts for a moment when they start, according to DTE Energy’s appliance usage guide.
How many watts common appliances use
Typical estimates from DTE Energy and Champion Power Equipment. Your appliance’s label is the best source.
| Appliance | Running watts | Starting watts | On 7,500 W? |
|---|---|---|---|
| Refrigerator/freezer | 750 | About 2,250 | Yes |
| Furnace fan (1/2 HP) | 600 | About 1,800 | Yes |
| Well pump (1/2 HP) | 1,000 | About 3,000 | Yes (240V, through a transfer switch) |
| Well pump (3/4 HP) | 1,500 | About 4,500 | Yes, started by itself |
| Sump pump (1/2 HP) | 1,000 | About 3,000 | Yes |
| Window air conditioner | 1,200 | About 2,000 | Yes |
| Microwave | 600 to 1,500 | Same | Yes |
| Space heater | 500 to 1,500 | Same | Yes |
| Electric water heater (50 gal) | 4,500 to 5,000 | Same | Only with most else off |
| Electric clothes dryer | About 4,850 | Higher | Only with most else off |
| Central air (3 ton) | About 6,000 | Much higher | Usually no |
Example: a whole-house outage plan
| Item | Running watts |
|---|---|
| Refrigerator | 750 |
| Furnace fan (gas furnace, 1/2 HP) | 600 |
| Well pump (1/2 HP) | 1,000 |
| Sump pump (1/2 HP) | 1,000 |
| Lights | 300 |
| TV and computer | 350 |
| Microwave | 1,000 |
| Total running | 5,000 |
| Plus one pump starting (3,000 minus 1,000) | +2,000 |
| Peak | 7,000 |
That fits a 7,500-watt generator, as long as both pumps don’t start at the exact same moment while the microwave is running. Skip the microwave and you have room for a window AC or a space heater.
Can a 7,500-watt generator run central air?
Usually not. DTE Energy lists a 3-ton central AC at about 6,000 running watts, and the compressor needs far more to start. DTE also tells GenerLink customers not to run central air or a heat pump on a portable generator. A smaller central unit with a soft-start kit sometimes works on a large portable generator, but check with an HVAC tech first. A window AC in one room is the practical choice.
Can it run power tools?
Yes. A 7,500-watt generator can run two or three tools at once. Champion lists a table saw at 1,800 running watts (2,500 starting) and a circular saw at 1,500 (2,000 starting). Running both, plus a work light and drill, stays well under 7,500 watts.
Connecting it to your house
A 7,500-watt generator usually has a 30-amp, 240-volt twist-lock outlet that can feed a transfer switch or interlock kit. That’s how you power hardwired loads like a furnace fan or well pump. Never plug it into a wall outlet. Here’s how to hook up a generator to your house. To compare current models, browse portable generators at Ace Hardware. (We may earn a commission if you buy through this link.)
Need less power? See what a 5,000-watt, 3,500-watt or 2,000-watt generator can run.
FAQ
Will a 7,500-watt generator run a whole house?
It’ll run the essentials of most homes if you manage the load. It won’t run everything at once, especially central air or electric heat.
How long will a 7,500-watt generator run on gas?
Many models run about 8 to 11 hours at half load on a full tank. Check your model’s spec sheet, and store fuel safely.
Can a 7,500-watt generator run an electric water heater?
Only if almost nothing else is running. A 50-gallon electric water heater can draw 4,500 to 5,000 watts.