Home › Guides › What size generator do I need? · Checked Nov 15, 2026
What size generator do I need?
The short answer
Add up what has to stay on, add room for the biggest motor starting, and compare. Three steps, one chart.
Typical running watts
Watts, typical. Motors can need up to double for a moment at startup. (HomeGuide) Your appliance labels beat any chart.
A common Michigan example
More detail
Match your number
| Your total | What fits |
|---|---|
| Under 7,200 W | A portable with a 30-amp outlet, plus DTE’s 30-amp device or an interlock |
| 7,200–9,600 W | A portable with a 50-amp outlet, plus DTE’s 40-amp device or an interlock |
| Over 9,600 W, or central AC with electric heat | Usually a standby: 13–20 kW covers most homes up to 3,000 sq ft |
DTE device limits; standby sizes from HomeGuide.
“I have 200-amp service”
That’s the most your house can draw, not what you need in an outage. DTE’s meter device works with 200-amp service or less. (DTE plan page)
- List what must stay on. Furnace, sump, fridge, a few lights.
- Add the running watts. Use labels or the chart.
- Add the biggest startup. Usually the sump or well pump.
- Compare to the table. Then pick the hookup.
Questions people ask
What size generator do I need to run my house?
Add the running watts of everything that must stay on, then add the biggest motor’s startup. Furnace fan, fridge, sump pump, lights and a TV come to about 3,200 running watts using HomeGuide’s typical figures, which fits a 7,200-watt setup.
What size generator for a 200-amp service?
Your panel’s 200-amp rating is not the generator size. Size the generator to what you need running in an outage. HomeGuide says 13 to 20 kW typically runs a whole home up to 3,000 square feet.
Can a 7,200-watt generator run central air?
A 4-ton central AC runs at about 8,500 watts in HomeGuide’s chart, more than 7,200. Smaller units vary; check your AC’s nameplate.
Keep reading
Two rules that save lives
Never run a generator in a garage, porch or near a window. Keep it 20 feet out, exhaust away.
Never backfeed through a dryer outlet. A ‘double-male’ cord can electrocute a lineman down the street. Your plan uses only safe, legal ways to connect.
Not sure which fits your house? A few taps about your home and what has to stay on. Free, and no email needed to see your plan.
Take the quiz: under 2 minutes- DTE: Surge Protection Plus plan details: www.dteenergy.com
- HomeGuide: Whole house generator cost (2026): homeguide.com
Lights Back On is not affiliated with DTE Energy. Educational content only; not electrical advice.