How many watt-hours do you need?
Pick what you'll actually run during an outage. Set the days you want covered. We'll size the battery, inverter, and surge headroom against every unit we've reviewed.
Step 1
What are you running?
Refrigerator (full-size)
150 W · 1200 W surge
1,200 Wh / day
Wi-Fi router + modem
25 W
600 Wh / day
LED bulb (each)
9 W
180 Wh / day
Phone charging (each)
15 W
60 Wh / day
Step 2
How long?
Result
You need at least
2,267
Wh capacity
241
W continuous
1,200
W surge
Daily draw: 2,040 Wh. We add a 10% inverter loss buffer and assume 90% usable capacity.
Best fit
EcoFlow Delta Pro
3,600 Wh · 3,600 W
$2,799
Runs your stack for ~12.1 hr per charge
All units
- ✓
EcoFlow Delta Pro
3,600 Wh · $2,799 · ~12.1 hr runtime
- ✓
Anker SOLIX F3800
3,840 Wh · $3,799 · ~12.9 hr runtime
- ×
EcoFlow River 3 Plus
286 Wh · $299 · underspec
- ×
Jackery Explorer 1000 v2
1,070 Wh · $799 · underspec
- ×
Bluetti AC180
1,152 Wh · $899 · underspec
- ×
Jackery Explorer 2000 Plus
2,042 Wh · $1,499 · underspec
Default wattages reflect manufacturer specs and Energy Star averages within ±15%. For critical loads, measure your appliance with a wattmeter for the most accurate input. Recommendations include a 10% inverter conversion buffer and assume 90% usable battery capacity.
How power station sizing actually works
Three numbers matter: total watt-hours of energy, continuous wattage of all loads at once, and peak surge wattage at any single startup.
1. Battery capacity (watt-hours)
Sum the watts of each appliance times the hours it runs each day. A fridge cycles roughly 8 hours per 24 at 200 W, so 1,600 Wh per day. A router runs 24 hours at 25 W, so 600 Wh. Add the rest. Multiply by your target days. That's the energy you need.
Add 10% for inverter conversion loss (DC battery to AC outlet). Then divide by 0.9 to account for usable battery capacity (LFP batteries protect the bottom 10% to extend cycle life). The math: required Wh = daily draw × days × 1.234.
2. Continuous wattage
The maximum wattage drawn when every appliance runs at the same time. A fridge (200 W) plus router (25 W) plus four LED bulbs (36 W) plus a CPAP (50 W) is 311 W continuous. Any unit above 500 W continuous handles this with headroom. A unit with a 1,000 W microwave on top needs 1,300+ W continuous.
3. Surge wattage
The largest single startup spike in your stack. Compressors (fridges, AC, freezers) draw 2× to 5× their steady wattage for 100 to 500 ms at startup. A 200 W fridge can spike to 1,200 W for half a second. If your unit's surge rating is below this, the inverter trips off and the appliance fails to start.
Common appliance wattage chart
Typical ranges for the appliances most readers ask about. Steady wattage drives capacity sizing; surge wattage drives inverter sizing.
| Appliance | Steady | Surge | Daily Wh |
|---|---|---|---|
| Refrigerator (full-size) | 100–250 W | 600–1,200 W | 1,500–2,500 Wh |
| Mini fridge | 60–100 W | 500–700 W | 600–900 Wh |
| Chest freezer | 80–150 W | 700–1,000 W | 800–1,500 Wh |
| CPAP (no humidifier) | 30–50 W | — | 300–400 Wh |
| CPAP with heater | 60–120 W | — | 500–900 Wh |
| Wi-Fi router + modem | 15–35 W | — | 400–800 Wh |
| LED light bulb | 8–12 W | — | 40–60 Wh |
| Window AC (5,000 BTU) | 450–700 W | 900–1,400 W | 4,000–5,500 Wh |
| Window AC (10,000 BTU) | 1,000–1,400 W | 2,000–2,800 W | 8,000–11,000 Wh |
| Microwave (1,000 W) | 900–1,100 W | 1,500 W | 200–400 Wh |
| Coffee maker | 800–1,200 W | — | 200–300 Wh |
| Sump pump (½ HP) | 600–900 W | 2,000–3,000 W | 600–1,200 Wh |
| Well pump (1 HP) | 1,200–1,800 W | 3,000–5,000 W | 1,500–2,500 Wh |
| Furnace blower (gas) | 500–800 W | 1,500–2,000 W | 3,000–5,000 Wh |
| Laptop charging | 45–90 W | — | 300–500 Wh |
| TV (55" LED) | 80–120 W | — | 300–500 Wh |
Why most online calculators get this wrong
Manufacturer-hosted calculators almost always recommend a unit one tier larger than you need. They optimize for your conversion, not your wallet. Capacity in watt-hours sells itself.
They also frequently skip three things: inverter conversion loss (real and meaningful), usable battery ratio (LFP batteries protect their bottom 10%), and surge wattage validation (the spec that kills compressor startup). Our calculator includes all three.
If your loads are simple (lights, internet, phone, laptop), a 500 to 1,000 Wh unit is plenty. Don't oversize. Better to spend the saved money on a 200 W solar panel and add unlimited runtime.
Sizing FAQ
Real questions from readers, answered directly.
How do I size a portable power station for my home?
Multiply each appliance's wattage by hours of daily use, sum them, then multiply by your target outage length in days. Add 10% for inverter conversion loss. The result is the minimum battery capacity in watt-hours. Then check the continuous wattage rating: it must exceed the sum of all appliances running simultaneously. Finally, check the surge rating: it must exceed the largest single-appliance startup spike (compressors, motors, pumps).
Why is the recommended capacity higher than my daily watt-hour draw?
Two reasons. First, pure sine wave inverters lose roughly 10% of input energy as heat during DC-to-AC conversion. Second, lithium iron phosphate batteries are typically rated at 90% usable capacity to preserve cycle life. So a 1,000 Wh draw needs about 1,200 Wh of nameplate capacity (1,000 / 0.9 / 0.9 = 1,234 Wh, rounded).
Does the calculator account for surge wattage?
Yes. Compressor-driven appliances (fridges, freezers, AC units, sump pumps, well pumps) draw 2× to 5× their steady wattage for 0.1 to 0.5 seconds at startup. The calculator finds the largest surge in your stack and recommends a unit whose surge rating exceeds it. If your unit's surge is too low, the inverter shuts off momentarily and the appliance fails to start.
Why do I need 240 V split-phase for some loads?
Most residential well pumps, electric water heaters, electric dryers, and central AC compressors are wired for 240 V split-phase, not single-phase 120 V. A single 120 V power station cannot drive these loads. The Anker SOLIX F3800 is the only sub-$4,000 portable power station with single-unit 240 V output. Two paired EcoFlow Delta Pros can also deliver 240 V via the Double Voltage Hub.
How accurate are the wattage figures in this calculator?
Steady-state wattages reflect manufacturer specs and Energy Star averages within ±15%. Compressor surge values vary by appliance age, ambient temperature, and motor condition. For critical loads (medical devices, well pumps), measure your specific appliance with a Kill A Watt or similar wattmeter for the most accurate input. Our defaults are conservative.
Can I extend runtime with solar panels?
Yes. Each kilowatt-hour of solar input per day can offset that much battery draw, effectively extending runtime indefinitely if your panels produce more than your daily draw. With 800 W of panels in clear midday sun (about 5,000 Wh of harvest per day), you can sustain a 4,000 Wh daily load with no grid charging needed. Cloudy days drop output by 40 to 80%.