I have not tested these units. The figures below are typical ranges compiled from manufacturer specifications and appliance labels. Your specific appliances will differ — always check the label on your own equipment. How I research this.
Most people buy the wrong size power station. Not because they’re careless, but because the two numbers that matter are easy to confuse, and manufacturers don’t go out of their way to clarify them.
Here’s what you actually need to know.
The two numbers that matter
Watts (W) measure power — how much a device draws at any given moment. This determines whether your power station can run a device at all.
Watt-hours (Wh) measure energy — the size of the tank. This determines how long it can run.
A power station rated 1,800W / 1,000Wh can power a 1,500W device — but only for about 40 minutes. It can power a 100W device for roughly 10 hours.
Get the first number wrong and the device won’t turn on. Get the second wrong and it turns off sooner than you expected.
The trap: starting watts
This is where most purchases go wrong.
Anything with a motor or compressor draws a large surge when it starts, then settles to a much lower draw. A refrigerator might run at 150W but demand 800W or more for the first second or two.
If your power station can’t supply that surge, the fridge simply won’t start — even though the running number looks comfortable.
Appliances with a start-up surge include: refrigerators, freezers, air conditioners, well pumps, sump pumps, power tools, and anything with a compressor.
Typical appliance draw
These are typical ranges, not guarantees. Efficiency varies enormously between models and model years. Check the label on your own appliance — it’s usually on the back or inside the door.
| Appliance | Running watts | Starting watts |
|---|---|---|
| LED light bulb | 8–12W | — |
| Laptop | 50–100W | — |
| Router + modem | 10–20W | — |
| Phone charger | 5–20W | — |
| Television | 50–200W | — |
| CPAP machine | 30–60W | — |
| Refrigerator | 100–250W | 600–1,200W |
| Chest freezer | 100–200W | 600–1,000W |
| Microwave | 600–1,200W | — |
| Coffee maker | 800–1,500W | — |
| Space heater | 750–1,500W | — |
| Window AC | 500–1,500W | 1,500–3,000W |
| Sump pump | 800–1,000W | 1,500–3,000W |
| Well pump | 1,000–2,000W | 2,000–4,000W |
How to calculate what you need
Step 1: List what must stay on
Be honest here. In a real outage, most people need far less than they think. A fridge, some lights, a phone charger, and a router covers most households.
Step 2: Add up running watts
Example: fridge (150W) + 4 LED bulbs (40W) + router (15W) + laptop (65W) = 270W running
Step 3: Add the single largest starting surge
You don’t add every surge together — appliances rarely start at the same instant. Add the largest one.
Example: 270W running + 800W fridge surge = your power station needs at least 1,070W surge capacity
Step 4: Work out how long you need it
Multiply running watts by hours: 270W × 8 hours = 2,160Wh
But a fridge doesn’t run continuously — its compressor cycles on and off, typically running about a third of the time. For appliances that cycle, use roughly one-third of the running figure for energy estimates.
This is an approximation, not a precise calculation. Build in margin.
Power station size calculator
Select what you need to keep running during an outage.
Running watts
0 W
Surge needed
0 W
Capacity
0 Wh
Select appliances to see a recommendation.
These are typical ranges, not guarantees. Check the label on your own appliance — efficiency varies widely between models. Inverter losses mean you receive roughly 85% of a battery’s rated capacity. This calculator is a shopping aid, not electrical advice.
Why manufacturer numbers mislead
Marketing numbers are often peak, not continuous. A unit advertised as "2,000W" may only sustain 1,500W continuously. The peak figure applies for a fraction of a second.
Look for continuous output in the specifications. That's the number that matters.
You never get 100% of rated capacity. Inverters lose energy as heat. A 1,000Wh battery typically delivers somewhere around 850–900Wh of usable AC power. Plan accordingly.
Rough sizing guide
| Use case | Continuous output | Capacity |
|---|---|---|
| Phones, laptop, lights | 300–500W | 300–500Wh |
| Above + router, CPAP | 500–1,000W | 500–1,000Wh |
| Above + refrigerator | 1,500–2,000W | 1,000–2,000Wh |
| Above + microwave, tools | 2,000–3,000W | 2,000–3,000Wh |
| Well pump, central AC | 3,000W+ | 3,000Wh+ |
If you need to run a well pump or central air conditioning, a battery power station is probably the wrong tool. Look at whole-home systems or standby generators, and talk to an electrician.
Safety notice
These calculations are estimates to help you shop. They are not a substitute for professional advice.
Never operate a fuel-powered generator indoors, in a garage, or in any enclosed space — including with the door open. Carbon monoxide is odorless and kills.
Consult a licensed electrician before connecting anything to your home's wiring, or before installing a transfer switch. I compare products. I don't certify what's safe for your home.