What Size Power Station Do I Need?
Three numbers decide it: the watts you run at once, the surge to start your biggest motor, and the watt-hours you use over the outage. Here is how to work out each one.
For a fridge, internet and lights through a typical overnight outage, most homes need 2 to 3 kWh and 2,000 W or more. For a 240V well pump or several circuits through a transfer switch, you need a 240V station of 4 kWh or more. The steps below get you to your own number.
Step 1: Output (watts at the same time)
Add up the running watts of everything you want on at once. The station's continuous output must be higher. Leave about 20% headroom.
| Appliance | Running | Startup | Average over a day |
|---|---|---|---|
| Refrigerator | 200 W | 1,200 W | 100 W |
| Chest freezer | 150 W | 800 W | 60 W |
| Wi-Fi router and modem | 20 W | 20 W | 20 W |
| LED lights (10 bulbs) | 100 W | 100 W | Depends on hours |
| CPAP (no humidifier) | 50 W | 50 W | 40 W while sleeping |
| Microwave | 1,000 W | 1,000 W | Short bursts |
| Furnace fan (½ hp) | 800 W | 2,350 W | Depends on weather |
| Sump pump (½ hp) | 1,050 W | 2,150 W | 100 to 300 W in storms |
| Space heater | 1,500 W | 1,500 W | 750 to 1,500 W |
| Well pump, 1 hp (240V) | 2,000 W | 4,000 W | 170 to 400 W |
Typical values. Check your appliance labels, or use a plug-in power meter for exact numbers.
Step 2: Surge (starting your biggest motor)
Motors in fridges, pumps and furnace fans pull 2 to 6 times their running watts for a moment when they start. Take your biggest startup number and add the running watts of everything else that will be on. The station's surge rating must be higher.
surge needed ≈ biggest startup W + other running W
Step 3: Capacity (watt-hours over the outage)
Multiply each appliance's average watts by the hours you need it, add them up, then divide by 0.85 to allow for inverter losses.
battery Wh needed ≈ total Wh used ÷ 0.85
Worked example: a 12-hour overnight outage
- Fridge: 100 W × 12 h = 1,200 Wh
- Router and modem: 20 W × 12 h = 240 Wh
- LED lights: 100 W × 4 h = 400 Wh
- CPAP: 40 W × 8 h = 320 Wh
Total: 2,160 Wh ÷ 0.85 ≈ 2,540 Wh. Peak running load is about 370 W, and the fridge start needs about 1,400 W of surge. A 2.5 to 3 kWh station such as the EcoFlow DELTA 3 Ultra Plus fits, with margin. A 2 kWh station gets close if you turn lights off earlier.
Worked example: a full day with a freezer
Fridge (2,400 Wh), freezer (1,440 Wh), router (480 Wh) and lights for 6 hours (600 Wh) add up to 4,920 Wh, or about 5,800 Wh of battery. That points to a 5 to 6 kWh station such as the Jackery Explorer 5000 Plus or EcoFlow DELTA Pro Ultra, or a smaller station plus solar panels. In winter, a furnace fan can add another 4 to 6 kWh a day.
Quick sizing table
| What you want to run | Output | Capacity | Stations that fit |
|---|---|---|---|
| Phones, router, laptop, lights, CPAP overnight | Under 500 W | 1 kWh | Anker SOLIX C1000 Gen 2 |
| Add the fridge, through a night or a day | Under 2,000 W | 2 to 3 kWh | Bluetti Elite 200 V2, EcoFlow DELTA 3 Ultra Plus, Jackery HomePower 3000 |
| Add a freezer, sump pump and microwave | 2,500 to 3,600 W | 3 kWh or more | EcoFlow DELTA 3 Ultra Plus, Bluetti Apex 300 |
| 240V well pump, furnace, circuits through a transfer switch | 4,000 to 7,200 W, 240V | 4 to 6 kWh, expandable | Anker SOLIX F3800 Plus, EcoFlow DELTA Pro 3, Jackery Explorer 5000 Plus, EcoFlow DELTA Pro Ultra |
Tips
- Size for the outages you actually get. Check how long your last few outages lasted.
- Solar panels stretch any station. Even 400 W of panels can replace a fridge's daily use on a sunny day.
- Expandable stations let you start smaller and add batteries later.
- Hard-wired loads such as well pumps and furnaces need a transfer switch installed by an electrician.
Skip the math: tick your appliances in the outage load calculator and it shows which stations can carry the load and for how long.
Specs and prices come from manufacturer listings and published reviews. We have not lab-tested these units. Prices change often, so check the current price before you buy.