How big of a generator do you need to run a house? Homeowners can often power most household appliances using between 3000 and 6500 watts. If your home city water, you can generally expect that 3000-5000 watts will cover your needs. If you have a well pump, you may need something larger such as 5000 to 6500 watt generator.

Additionally, keep in mind central AC has the highest power consumption, with a 24,000 BTU installation using close to 5000 running watts. A 10,000 BTU installation, however, uses around 1500 watts, while a 12,000 BTU window unit uses 3250.