The short answer
To keep a refrigerator, Wi-Fi router, LED lights, a laptop and a TV going through a 24-hour outage, you need a power station of at least about 3,350 Wh, with 410 W of continuous output and a 1,460 W surge for the fridge's compressor. The fridge alone is 1,200 Wh a day.
Energy by appliance
Typical watts and the hours a day each appliance actually runs (a fridge's compressor only part of the time), so the energy it uses in a day.
| Appliance | Watts | Hours a day | Wh a day |
|---|---|---|---|
| Heating & cooling | |||
| Space heater | 1,500 | 8 | 12,000 |
| Window air conditioner | 900 | 8 | 7,200 |
| Portable air conditioner | 1,200 | 8 | 9,600 |
| Central air conditioner (3 ton) | 3,500 | 8 | 28,000 |
| Ceiling fan | 50 | 8 | 400 |
| Box or window fan | 100 | 8 | 800 |
| Dehumidifier | 500 | 12 | 6,000 |
| Electric blanket | 100 | 8 | 800 |
| Furnace blower fan | 500 | 8 | 4,000 |
| Kitchen | |||
| Refrigerator | 150 | 8 | 1,200 |
| Chest freezer | 80 | 8 | 640 |
| Microwave | 1,100 | 0.25 | 275 |
| Electric oven | 2,400 | 1 | 2,400 |
| Electric stove burner | 1,500 | 1 | 1,500 |
| Induction cooktop | 1,800 | 1 | 1,800 |
| Air fryer | 1,500 | 0.5 | 750 |
| Slow cooker | 200 | 8 | 1,600 |
| Electric pressure cooker | 1,000 | 0.5 | 500 |
| Coffee maker | 1,000 | 0.5 | 500 |
| Electric kettle | 1,500 | 0.25 | 375 |
| Toaster | 1,100 | 0.1 | 110 |
| Toaster oven | 1,200 | 0.5 | 600 |
| Dishwasher | 1,200 | 0.75 | 900 |
| Laundry & cleaning | |||
| Clothes washer | 500 | 1 | 500 |
| Electric clothes dryer | 3,000 | 0.75 | 2,250 |
| Clothes iron | 1,400 | 0.25 | 350 |
| Vacuum cleaner | 1,000 | 0.25 | 250 |
| Hair dryer | 1,500 | 0.25 | 375 |
| Electronics | |||
| TV (55 inch LED) | 100 | 5 | 500 |
| Game console | 150 | 3 | 450 |
| Desktop computer | 150 | 8 | 1,200 |
| Laptop | 50 | 8 | 400 |
| Computer monitor | 30 | 8 | 240 |
| Wi-Fi router | 10 | 24 | 240 |
| Lighting | |||
| LED bulb (60 W equivalent) | 9 | 5 | 45 |
| Incandescent bulb | 60 | 5 | 300 |
| Lights (about 10 LED bulbs) | 100 | 5 | 500 |
| Water & outdoor | |||
| Electric water heater | 4,500 | 3 | 13,500 |
| Pool pump | 1,500 | 8 | 12,000 |
| Hot tub | 4,000 | 2 | 8,000 |
| Well pump | 750 | 1 | 750 |
| Sump pump (1/3 to 1/2 hp) | 800 | 1 | 800 |
| Garage door opener | 550 | 0.05 | 28 |
How it works
The formula
We add up the energy each appliance uses during the outage, allow for the inverter's loss, and add up what runs at once for the inverter size.
loads you switch on (lights, TV, cooking): energy = watts × hours a day × each day the outage touches
never more than the outage itself
battery Wh = energy ÷ 0.85
continuous W = sum of running watts
surge W = continuous + the largest single start
Assumptions
- Watts are typical running figures from the U.S. Department of Energy Energy Saver list; starting watts from generator makers' wattage guides (Honda, Generac, Champion). Hours a day are typical use, with cycling appliances counting only the hours the compressor or motor runs.
- About 15% of stored energy is lost in the inverter that turns the battery's DC into AC; many portable stations lose 10 to 15%, more at very light loads.
- Loads that cycle on their own (a fridge's compressor, a router, a furnace blower, pumps) have their daily hours spread over the outage. Loads you switch on (lights, TV, laptop, cooking) count their full daily hours for each day the outage touches, so a short evening outage still counts an evening of lights. In cold weather a furnace blower or a sump pump in a storm can run much more than typical; add them as your own load with longer hours if so.
- We count everything checked as running at the same time for the continuous rating, which is the safe assumption.
- Above about 6 kWh, a wired-in home battery is the usual choice; portable stations top out around there.
Worked example: essentials for a day
- Refrigerator: 150 W × 8 h = 1,200 Wh
- TV (55 inch LED): 100 W × 5 h = 500 Wh
- Laptop: 50 W × 8 h = 400 Wh
- Wi-Fi router: 10 W × 24 h = 240 Wh
- Lights (about 10 LED bulbs): 100 W × 5 h = 500 Wh
- Total 2,840 Wh ÷ 0.85 = 3,341 Wh battery, 410 W continuous, 1,460 W surge
Too big or too small
- Too small a battery: it runs flat before the power's back. Add a margin, or plan to recharge from solar or a car.
- Too small an inverter: it shuts off when the fridge or a pump starts. Check the surge rating.
- Too big: mostly wasted money and weight; a bigger battery is only worth it if you'll use it.
- Heat and cooking drain it fast. A space heater, kettle or hair dryer empties a 1,000 Wh station in under an hour.
Questions people ask
What size power station do I need to run a refrigerator?
A typical refrigerator draws about 150 W while its compressor runs, about 8 hours a day, and up to about 1,200 W for a moment when it starts. That's 1,200 Wh a day at the outlet, or a battery of at least 1,412 Wh after inverter losses, with an inverter that can surge to at least 1,200 W.
How long will a power station run my essentials?
Divide its capacity by the energy you use. A fridge, router, LED lights, a laptop and a TV use about 2,840 Wh a day at the outlets, so a 2,000 Wh station lasts about 0.6 days and a 1,000 Wh one about 0.3.
What size battery for a CPAP overnight?
A CPAP without its heated humidifier often draws 30 to 60 W; at 40 W for 8 hours that's 320 Wh, so a battery of at least 376 Wh. With the humidifier on it can use several times more; check your machine's power supply label and its maker's battery guidance.
Power station or generator?
A power station is silent, has no fumes and can run indoors, but it holds a fixed amount of energy and needs recharging (from the wall, solar panels or a car). A generator runs as long as you have fuel but must stay outdoors. For a 3-day outage with a freezer, furnace blower and well pump you'd need about 25.9 kWh, which is home-battery or generator territory.
What do the watts and watt-hours on a power station mean?
Watt-hours (Wh) is how much energy the battery stores: it sets how long things run. Watts (W) is how much it can deliver at once: its continuous output must cover everything running together, and its surge rating the biggest motor start.