Qty
Details & exact specs
- Running
- 275 W
- Starting
- 1,000 W
- Voltage
- 120 V
BACKUP POWER, WITHOUT THE GUESSWORK
Generator Size Calculator for Home Backup Power
We help you choose a generator that fits your power needs. Our home and RV calculators evaluate your appliance loads, starting demand, and operating headroom using a documented sizing method, so you can compare setups before you buy.
MAKE IT YOUR SETUP
Your loads 4
Qty
Details & exact specs
- Running
- 115 W
- Starting
- 115 W
- Voltage
- 120 V
Qty
Details & exact specs
- Running
- 15 W
- Starting
- 15 W
- Voltage
- 120 V
Qty
Details & exact specs
- Running
- 60 W
- Starting
- 60 W
- Voltage
- 120 V
Start with typical values. Fine-tune any appliance with its exact specifications.
Heat pumps or whole-home systems?
These can include outdoor units, air handlers and auxiliary heaters. They need a whole-system review.
SMALL CHANGES. LESS DEMAND.
Ways to reduce the size you need
These actions change your selected loads. They never change the calculation assumptions.
THE METHOD, MADE SIMPLE
Running power.
Starting headroom.
We add the running watts of your enabled appliances, then allow for the largest single motor startup. The running recommendation includes a 20% operating reserve.
Example: a 200 W refrigerator with 1,200 W starting power needs 250 W recommended running capacity and 1,200 W starting capability when used alone.
01Add your running loadsWatts × quantity for each enabled appliance.
02Allow for one motor startingThe largest additional startup, one unit at a time.
03Leave operating headroomRunning load ÷ 0.80, rounded up.
Power safely. Every time.
Never run a portable generator indoors, in a garage, or near openings. Do not backfeed a home electrical system. Have transfer equipment installed according to applicable electrical rules.
A few useful things to know
Are starting watts added for every appliance?
No. This model assumes one motor starts at a time while the other selected loads are running. Simultaneous startup needs a separate assessment.
Can I enter amps or use LRA?
Use real input watts. Voltage × current is apparent power (VA), not real watts without a known power factor. LRA is not a direct starting-watts value.
Where do the values come from?
Values come from the reviewed BGT 1.2.2 dataset. Open a load’s source details for manufacturer and planning references. Estimates and exact overrides remain clearly labeled.
582 W runningPeak 1,190 W · 120V
View result ↑Result: 582 watts running, 1,190 watts starting.