Home backup power calculator
Pick the appliances you need through an outage. We’ll size a generator or a battery power station for them, check every model we track, and show the math.
Rule of thumb: add up the running watts of everything you need, add the biggest motor’s starting surge, then about 20% headroom. For a fridge, sump pump, furnace fan and lights that’s about 4,000–4,500 W.
Pick the closest match, then fine-tune the list below.
Fridge, sump pump, furnace fan, five lights and the Wi-Fi router. Change anything below.
9 items · adjust quantities or edit watts
Refrigerator (full-size)
400 W running · 1,200 W starting
Sump pump 1/2 HP
1,050 W running · 2,150 W starting
Furnace fan 1/3 HP (gas or oil)
700 W running · 1,400 W starting
LED bulb (each)
15 W running · 15 W starting
Wi-Fi router or modem
20 W running · 20 W starting
86 household appliances, tools and RV loads
Refrigerator (full-size)
400 W running · 1,200 W starting
Freezer (chest or upright)
500 W running · 1,000 W starting
Mini fridge or cooler
100 W running · 600 W starting
Sump pump 1/3 HP
800 W running · 1,600 W starting
Sump pump 1/2 HP
1,050 W running · 2,150 W starting
Well pump 1/2 HP
1,000 W running · 2,000 W starting
Well pump 1 HP
2,000 W running · 4,000 W starting
Electric water heater
4,500 W running · 4,500 W starting
Furnace fan 1/8 HP (gas or oil)
300 W running · 500 W starting
Furnace fan 1/6 HP (gas or oil)
500 W running · 750 W starting
Furnace fan 1/4 HP (gas or oil)
600 W running · 1,000 W starting
Furnace fan 1/3 HP (gas or oil)
700 W running · 1,400 W starting
Furnace fan 1/2 HP (gas or oil)
875 W running · 2,350 W starting
Window air conditioner 5000 BTU
600 W running · 1,200 W starting
Window air conditioner 10000 BTU
1,500 W running · 2,400 W starting
Central air conditioner 2 ton
2,500 W running · 4,500 W starting
Central air conditioner 3 ton
3,500 W running · 6,000 W starting
Central air conditioner 4 ton
5,000 W running · 8,000 W starting
Electric space heater
1,500 W running · 1,500 W starting
Radiant heater
1,300 W running · 1,300 W starting
Ceiling fan
75 W running · 75 W starting
Box or window fan
200 W running · 200 W starting
Microwave oven
1,500 W running · 1,500 W starting
Coffee maker
1,200 W running · 1,200 W starting
Toaster
1,200 W running · 1,200 W starting
Electric range (one burner)
2,400 W running · 2,400 W starting
Electric fry pan
1,500 W running · 1,500 W starting
Electric grill (tabletop)
1,650 W running · 1,650 W starting
Slow cooker
270 W running · 270 W starting
Blender
600 W running · 1,200 W starting
Air fryer
1,500 W running · 1,500 W starting
Portable induction cooktop
1,800 W running · 1,800 W starting
Electric smoker
1,200 W running · 1,200 W starting
Dishwasher (cool dry cycle)
216 W running · 540 W starting
Dishwasher (heated dry)
2,400 W running · 2,400 W starting
Washing machine
1,200 W running · 2,300 W starting
Electric clothes dryer
6,000 W running · 6,750 W starting
Gas clothes dryer
700 W running · 2,200 W starting
TV (flat screen 20 to 55 inch)
400 W running · 400 W starting
Desktop computer
800 W running · 800 W starting
Laptop or phone charger
250 W running · 250 W starting
LCD monitor
30 W running · 30 W starting
Printer
600 W running · 600 W starting
Wi-Fi router or modem
20 W running · 20 W starting
Satellite receiver
250 W running · 250 W starting
Radio
200 W running · 200 W starting
Home security system
40 W running · 40 W starting
LED bulb (each)
15 W running · 15 W starting
CPAP machine (no heated humidifier)
60 W running · 60 W starting
CPAP machine (heated humidifier)
120 W running · 120 W starting
RV air conditioner 11000 BTU
1,010 W running · 1,600 W starting
RV air conditioner 13500 BTU
2,000 W running · 3,500 W starting
RV air conditioner 15000 BTU
2,500 W running · 4,500 W starting
RV refrigerator
600 W running · 1,000 W starting
RV microwave
1,200 W running · 1,200 W starting
RV water heater (electric)
1,500 W running · 1,500 W starting
String or LED camp lights
200 W running · 200 W starting
Portable projector
300 W running · 300 W starting
Garage door opener
720 W running · 1,420 W starting
Circular saw (7-1/4 in)
1,800 W running · 3,600 W starting
Table saw (10 in)
3,000 W running · 6,000 W starting
Miter saw (10 in)
1,800 W running · 3,600 W starting
Reciprocating saw
1,200 W running · 2,400 W starting
Angle grinder (4-1/2 in)
1,800 W running · 3,600 W starting
Electric drill (1/2 in)
600 W running · 1,200 W starting
Hammer drill
1,200 W running · 2,400 W starting
Belt sander
1,200 W running · 2,400 W starting
Air compressor 1/2 HP
975 W running · 1,600 W starting
Air compressor 1 HP
1,600 W running · 4,500 W starting
Air compressor 2 HP
2,500 W running · 7,500 W starting
Air compressor 3 HP
3,500 W running · 10,500 W starting
Pressure washer 1500 PSI
1,500 W running · 3,000 W starting
Pressure washer 2500 PSI
2,500 W running · 5,000 W starting
Welder (120V)
2,500 W running · 5,000 W starting
Welder (240V)
8,000 W running · 16,000 W starting
Work light (LED)
25 W running · 25 W starting
Work light (halogen 500 W)
500 W running · 500 W starting
Job-site heater
3,000 W running · 3,000 W starting
Battery charger (heavy duty)
2,000 W running · 2,000 W starting
Motor 1/4 HP (capacitor-start capacitor-run)
400 W running · 850 W starting
Motor 1/3 HP (capacitor-start capacitor-run)
450 W running · 975 W starting
Motor 1/2 HP (capacitor-start capacitor-run)
600 W running · 1,300 W starting
Motor 3/4 HP (capacitor-start capacitor-run)
850 W running · 1,900 W starting
Motor 1 HP (capacitor-start capacitor-run)
1,000 W running · 2,300 W starting
Motor 1.5 HP (capacitor-start capacitor-run)
1,600 W running · 3,200 W starting
Motor 2 HP (capacitor-start capacitor-run)
2,000 W running · 3,900 W starting
4,500W class
Your 3,345 W peak + 20% margin = 4,014 W, rounded up to the next 500 W.
Of the 11 generators we track:1 fits well2 fit, but tight8 won’t work
Rated 5,500 W covers your 3,345 W peak plus 20%.
Published runtime: 6.4 h at full rated load · 16 h at 1/4 load · 5.1 gal tank. At your load (41%): between 6.4 h and 16 h per tank (estimate between the published points).
Covers your 3,345 W peak, but is under the 4,014 W target.
Published runtime: 8.0 h at 50% load · 2.37 gal tank.
Covers your 3,345 W peak, but is under the 4,014 W target.
Starting output of 3,000 W is below your 3,345 W peak.
Published runtime: 6.9 h at full rated load · 19.6 h at 1/4 load · 3.4 gal tank. At your load (80%): between 6.9 h and 19.6 h per tank (estimate between the published points).
Your running load plus 20% needs 2,694 W; this is rated 1,200 W.
Your running load plus 20% needs 2,694 W; this is rated 1,600 W.
Your running load plus 20% needs 2,694 W; this is rated 1,700 W.
Your running load plus 20% needs 2,694 W; this is rated 1,800 W.
Your running load plus 20% needs 2,694 W; this is rated 1,800 W.
Your running load plus 20% needs 2,694 W; this is rated 1,850 W.
Your running load plus 20% needs 2,694 W; this is rated 1,850 W.
Your list uses about 12.5–13.5 kWh a day.
refrigerator: 1.1–2.1 kWh a day (not sure, ENERGY STAR/DOE ranges), not its nameplate watts. Hours per day: sump pump 2 h, furnace fan 12 h, LED bulb 6 h, Wi-Fi router or modem all day. These are example estimates; change them under “Edit watts and hours”.Of the 11 power stations we track:3 fit well1 fits, but tight7 won’t work
3,600 W continuous covers your 2,245 W load plus 20%.
6,000 W continuous covers your 2,245 W load plus 20%.
4,000 W continuous covers your 2,245 W load plus 20%.
2,400 W continuous covers your 2,245 W load, but not the 20% margin.
Continuous output of 600 W is below your 2,245 W running load.
Continuous output of 1,800 W is below your 2,245 W running load.
Continuous output of 1,800 W is below your 2,245 W running load.
Continuous output of 2,000 W is below your 2,245 W running load.
Continuous output of 1,500 W is below your 2,245 W running load.
Continuous output of 1,800 W is below your 2,245 W running load.
Continuous output of 2,200 W is below your 2,245 W running load.
Generac GP3500iO with your list
Works, little headroomCovers your 3,345 W peak, but is under the 4,014 W target.
Tap Add to put it on your list.
The unit can start it, but not on top of your current list.
Sources suggest 20–25% headroom over peak demand TTH · medium.
Inverter and battery losses. 85% is a common rule OUP · medium; EcoFlow’s own runtime examples imply 80%.
Read the full method, including why fridge runtime uses daily kWh instead of nameplate watts.
Open the My unit tab above, or start from its size:
Every appliance we track, checked against a 2,000 W generator.
Every appliance we track, checked against a 3,500 W generator.
Every appliance we track, checked against a 5,000 W generator.
Every appliance we track, checked against a 7,500 W generator.
A power station (sometimes sold as a “solar generator”) is a battery with outlets. It’s silent, has no exhaust and can run indoors, but it stores a fixed amount of energy: a 1,024 Wh unit runs a fridge for most of a day. Most portable stations supply 120V only.
A generator makes power from fuel for as long as you refuel it and handles big motor loads more cheaply, but it must run outdoors, 20 feet from the house, and it’s loud. The planner checks both against your list. Compare them in detail.
Usually not everything at once. A 6,500 W generator comfortably covers essentials like a fridge, a sump pump, a furnace fan, lights and electronics. Big loads eat it quickly: a 3-ton central AC runs at about 3,500 W and needs about 6,000 W to start, and an electric dryer draws about 6,000 W on its own. Add your own list above to check.
It depends on the loads, not the square footage. 10,000 W runs most homes’ essentials plus a window AC or two, but not an electric water heater (4,500 W), a dryer (6,000 W) and a central AC together. Whole-house standby generators are usually sized by a dealer from your panel’s loads.
Motors draw a burst of power for a second or two when they start, but they rarely start at the same instant. The standard method adds all running watts, then the single largest extra starting surge, then about 20% headroom. Adding every surge together oversizes the generator, often by thousands of watts.
Yes, with a heavy-duty outdoor extension cord rated for the load, run from the generator outside to the fridge inside. The generator itself must stay outdoors, at least 20 feet from the house (CPSC). Never plug a generator into a wall outlet to power the house.
At least 20 feet, with the exhaust pointed away from windows, doors and vents, according to the U.S. Consumer Product Safety Commission. Never in a garage, basement or shed, even with the door open. Keep a working CO alarm inside.
Roughly 15–19 hours for a top-freezer fridge on a 1,024 Wh station, because a fridge’s compressor cycles on and off. Full-size fridges use about 1.1–2.1 kWh a day depending on type. Pick “Fridge + freezer” above and open the Power stations tab for every model we track.
Appliance watts come from the Honda and Champion generator wattage charts, with a few from Generac and secondary sources marked lower confidence. Model specs come from each manufacturer’s product page, checked 2026-09-26. Safety guidance comes from the U.S. Consumer Product Safety Commission and Generac. See every source.
