Generator & power station calculator
What size generator or power station do I need?
Pick the devices you want to keep running during an outage or on a trip, and get the battery or generator size to buy.Pick your devices, get the size to buy.
Quick start
How long should it last?
120 V · US & Canada
Your devices
Popular
- Refrigerator (full-size)24 h/day · 180 WCustom values
The compressor cycles on and off, so average use is far below running watts.
- CPAP (no humidifier)40 WCustom values
Check your machine's power supply label. Running it from DC uses less battery.
- Wi-Fi router + modem24 h/day · 20 WCustom values
- LED lights (5 bulbs)5 h/day · 50 WCustom values
- Phone charging3 h/day · 15 WCustom values
- TV (55" LED)4 h/day · 100 WCustom values
- Microwave (1,000 W cooking)1,500 WCustom values
A "1,000 W" microwave draws about 1,500 W from the outlet.
- Space heater1,500 WCustom values
- Sump pump (½ HP)1,050 W · 2,150 W startCustom values
Pumps run in short bursts. Hours here means total pumping time per day.
- Chest freezer100 W · 700 W startCustom values
Kitchen
- Mini fridge80 W · 400 W startCustom values
- Coffee maker1,000 WCustom values
- Electric kettle1,500 WCustom values
- Hot plate / one stove burner1,500 WCustom values
Medical, internet & phones
- CPAP with heated humidifier90 WCustom values
- Starlink (Standard)75 WCustom values
- Starlink Mini30 WCustom values
- Laptop65 WCustom values
Heating & cooling
- Box fan8 h/day · 75 WCustom values
- Electric blanket100 WCustom values
- Window AC (10,000 BTU)900 W · 2,700 W startCustom values
- Gas furnace blower (½ HP)875 W · 2,350 W startCustom values
- Central AC (3-ton)3,500 W · 9,000 W startCustom values
A soft-start kit can cut starting watts by more than half.
Lights & electronics
- Desktop PC + monitor250 WCustom values
- Game console150 WCustom values
Whole-home systems
- Well pump (½ HP)1,000 W · 2,100 W startCustom values
- Washing machine500 W · 1,150 W startCustom values
- Electric water heater4,500 WCustom values
- Electric clothes dryer5,400 W · 6,750 W startCustom values
- Garage door opener550 W · 1,100 W startCustom values
Camping & RV
- 12 V portable fridge45 W · 90 W startCustom values
- 12 V diesel heater30 W · 150 W startCustom values
The glow plug draws extra power for a few minutes at start-up.
- RV air conditioner (13,500 BTU)1,500 W · 3,000 W startCustom values
Tools
- Circular saw1,400 W · 2,300 W startCustom values
- Air compressor (1 HP)1,600 W · 4,500 W startCustom values
Nothing matches that search. Use “+ Your own device” to add it with its watts.
How the calculator sizes your backup power
Every device has two numbers that matter. Running watts is what it draws while it works. Starting watts is the short surge a motor or compressor needs to get going. We add up the running watts of everything you picked, then add the extra starting watts of the single biggest motor, because motors rarely start at exactly the same moment.
For a power station the battery matters as much as the output. We multiply each device's average draw by its hours of use, scale that to your outage length, and divide by 0.85, because about 15% is lost in the inverter and battery reserve. Then we round up to a common battery size.
For a portable generator we add a 10% margin to the running watts so it isn't working flat out. When the load includes central AC, a well pump, an electric water heater or a dryer, we also show the size of a standby generator wired to your panel.
Appliance wattage chart
Typical figures for modern appliances in the US, Canada, the UK and Australia. Most devices draw the same watts everywhere. Where 230 V models are more powerful (kettles, heaters, water heaters, dryers), the UK & Australia figure is shown underneath. Your device's label always wins.
| Device | Running W | Starting W | Typical use / day |
|---|---|---|---|
| Refrigerator (full-size)Kitchen | 180 | 1,200 | 1,440 Wh |
| Chest freezerKitchen | 100 | 700 | 840 Wh |
| Mini fridgeKitchen | 80 | 400 | 720 Wh |
| Microwave (1,000 W cooking)Kitchen | 1,500 | — | 375 Wh |
| Coffee makerKitchen | 1,000 | — | 250 Wh |
| Electric kettleKitchen | 1,500UK & AU: 3,000 | — | 225 WhUK & AU: 450 Wh |
| Hot plate / one stove burnerKitchen | 1,500 | — | 900 Wh |
| CPAP (no humidifier)Medical, internet & phones | 40 | — | 240 Wh |
| CPAP with heated humidifierMedical, internet & phones | 90 | — | 480 Wh |
| Wi-Fi router + modemMedical, internet & phones | 20 | — | 360 Wh |
| Starlink (Standard)Medical, internet & phones | 75 | — | 480 Wh |
| Starlink MiniMedical, internet & phones | 30 | — | 200 Wh |
| Phone chargingMedical, internet & phones | 15 | — | 30 Wh |
| LaptopMedical, internet & phones | 65 | — | 225 Wh |
| Box fanHeating & cooling | 75 | — | 480 Wh |
| Electric blanketHeating & cooling | 100 | — | 480 Wh |
| Space heaterHeating & cooling | 1,500UK & AU: 2,000 | — | 6,000 WhUK & AU: 8,000 Wh |
| Window AC (10,000 BTU)Heating & cooling | 900 | 2,700 | 4,500 Wh |
| Gas furnace blower (½ HP)Heating & cooling | 875 | 2,350 | 4,800 Wh |
| Central AC (3-ton)Heating & cooling | 3,500 | 9,000 | 24,000 Wh |
| LED lights (5 bulbs)Lights & electronics | 50 | — | 250 Wh |
| TV (55" LED)Lights & electronics | 100 | — | 360 Wh |
| Desktop PC + monitorLights & electronics | 250 | — | 720 Wh |
| Game consoleLights & electronics | 150 | — | 360 Wh |
| Sump pump (½ HP)Whole-home systems | 1,050 | 2,150 | 1,050 Wh |
| Well pump (½ HP)Whole-home systems | 1,000 | 2,100 | 1,000 Wh |
| Washing machineWhole-home systems | 500 | 1,150 | 400 Wh |
| Electric water heaterWhole-home systemsUK & AU: Immersion water heater | 4,500UK & AU: 3,000 | — | 9,000 WhUK & AU: 6,000 Wh |
| Electric clothes dryerWhole-home systems | 5,400UK & AU: 2,500 | 6,750UK & AU: 3,000 | 4,500 WhUK & AU: 2,200 Wh |
| Garage door openerWhole-home systems | 550 | 1,100 | 55 Wh |
| 12 V portable fridgeCamping & RV | 45 | 90 | 480 Wh |
| 12 V diesel heaterCamping & RV | 30 | 150 | 120 Wh |
| RV air conditioner (13,500 BTU)Camping & RV | 1,500 | 3,000 | 7,800 Wh |
| Circular sawTools | 1,400 | 2,300 | 700 Wh |
| Air compressor (1 HP)Tools | 1,600 | 4,500 | 800 Wh |
Frequently asked questions
What size generator do I need to run a house?
Add up the running watts of everything you want on at the same time, then add the extra starting watts of the single biggest motor (usually the AC, well pump or fridge). Essentials like a fridge, lights, internet and a sump pump usually fit a 3,500–5,000 W portable generator. Running central AC, an electric water heater or a well pump together usually needs a 14–22 kW standby generator.
What size power station do I need for a refrigerator?
A modern full-size fridge uses about 1–1.5 kWh per day, so a 2,000 Wh power station keeps it running for roughly a day. The power station also needs about 300 W of continuous output and enough surge (around 1,200 W) for the compressor to start.
Can a power station run a CPAP all night?
Yes. A CPAP without a humidifier uses about 30–40 W, so 8 hours needs roughly 300 Wh including losses. With a heated humidifier plan for about 500–600 Wh per night. Running the CPAP from its DC adapter instead of the AC outlet saves around 10–15% of the battery.
What is the difference between running watts and starting watts?
Running watts are what a device draws while it works. Starting (surge) watts are the short burst a motor or compressor needs for a second or two when it switches on, often 2–3 times the running watts. Your generator or power station must cover both.
How long will a 1,000 Wh power station run a fridge?
About 850 Wh of a 1,000 Wh power station is usable after inverter losses. A fridge averaging 60 W runs about 14 hours on that. Older fridges, hot rooms and frequent door opening shorten that time.