What Size Power Station Do I Need? The 10-Minute Worksheet
Power stations are sold by two headline numbers — watt-hours (how much energy the battery stores) and watts (how fast it can deliver that energy). Buy on vibes and you'll get one of the classic failure modes: a unit that shuts down the moment your fridge compressor kicks, or a 40-pound box you spent $1,000 on to charge phones. Ten minutes of arithmetic prevents both.
Step 1 — List your loads and their watts
Everything you want to run has a wattage, printed on a label or in its manual. Typical values (labels beat our table, always):
| Device | Running watts | Surge watts (startup) |
|---|---|---|
| Phone charger | 10–20 | — |
| Wi-Fi router + modem | 10–20 | — |
| LED lamp | 5–15 | — |
| Laptop | 40–65 | — |
| CPAP (humidifier off / on) | 30–60 / 70–150 | — |
| TV (LED, 50") | 60–150 | — |
| Refrigerator (modern, mid-size) | 100–250 avg while running | 700–1,200 |
| Sump pump (1/3 HP) | 700–800 | 1,300–2,900 |
| Microwave | 1,000–1,500 | — |
| Space heater | 750–1,500 | — |
| Window AC (5,000 BTU) | 400–600 | 1,200–1,800 |
Step 2 — The two correction factors everyone skips
Factor 1: Inverter efficiency (~85%). Converting DC battery power to AC wall power costs energy. A "1,024 Wh" unit delivers roughly 870 Wh to your devices. Every honest runtime estimate starts by multiplying capacity by ~0.85.
Factor 2: Duty cycle. Fridges, sump pumps, and AC compressors don't run continuously — a fridge compressor runs maybe 30–40% of the time with the door shut. Multiplying running watts by duty cycle turns a scary 150 W into a manageable ~55 Wh per hour. Skipping this factor makes fridges look impossible; applying it dishonestly (some marketing uses 20%) makes runtimes look magical. We use 35% for a modern fridge.
Step 3 — The formula
…and separately check: surge rating > biggest single startup spike, and continuous rating > everything running at once.
Worked example: fridge + router + phones + two lamps on a 1,024 Wh unit
- Usable energy: 1,024 × 0.85 ≈ 870 Wh
- Fridge: 150 W × 35% = 52.5 Wh/h · Router: 15 W × 100% = 15 Wh/h · Lamps: 20 W × 50% = 10 Wh/h · Phones: ~5 Wh/h averaged
- Total draw ≈ 82 Wh per hour
- Runtime: 870 ÷ 82 ≈ 10.5 hours — a full night, with the fridge protected.
Step 4 — Match your total to a capacity class
| Class | Covers | Typical cost (Aug 2026) | Example unit (published specs) |
|---|---|---|---|
| ~300 Wh | Phones, router, lamp, CPAP nights, laptop top-ups. No fridge. | $200–280 | Bluetti Elite 30 V2 — 288 Wh / 600 W |
| ~1,000 Wh | All of the above plus a fridge for 12–18 h. The most useful class for most homes. | $450–550 | EcoFlow Delta 3 Classic — 1,024 Wh / 1,800 W (3,600 W surge) · Jackery Explorer 1000 v2 — 1,070 Wh / 1,500 W |
| ~2,000 Wh | Fridge for 1–1.5 days plus electronics; microwave in bursts; small AC briefly. | $650–950 | EcoFlow Delta 3 Max — 2,048 Wh / 2,400 W · Jackery Explorer 2000 Plus — 2,042 Wh / 3,000 W, expandable to 24 kWh |
| 3,000+ Wh | Multi-day fridge duty, sump pump coverage, "most of the house except HVAC." | $1,100–1,900 | Bluetti Elite 300 — 3,014 Wh / 2,400 W (4,800 W surge) · Jackery HomePower 3600 Plus — 3,584 Wh / 3,600 W |
Prices were checked on Amazon in August 2026 — several were mid-promotion, and this category discounts aggressively, so treat ranges as indicative and check current prices.
Common sizing questions, answered with the formula
How long will a power station run a refrigerator?
Apply the chain: usable Wh ÷ (150 W × 35%). A 300 Wh unit: ~4–5 hours — not a fridge solution. A 1 kWh unit: 12–18 hours. A 2 kWh unit: a day and a half. A 3 kWh+ unit: 2–3 days. Verify the surge rating covers your compressor's startup (700–1,200 W typical).
What size for a CPAP?
A CPAP at 40 W with the humidifier off uses ~320 Wh per 8-hour night — so a 300 Wh class unit is roughly one night, a 1 kWh unit is 2–3 nights. Turn the heated humidifier off during outages; it can triple the draw. (Check your specific machine's DC option too — running on DC skips inverter losses entirely.)
What size for Wi-Fi and phones only?
A router at 15 W needs 360 Wh per day. Any ~300 Wh unit buys you most of a day of connectivity; the class's 10 ms-UPS models can sit inline year-round so the router never even blinks.
Do I need to size up for solar recharging?
No — solar input doesn't change the sizing math, it extends it. A 200 W panel in real conditions returns roughly 600–800 Wh on a good day. That's most of a fridge-day added per sunny day on a 1 kWh unit. Panel input caps vary per unit; check the spec sheet's "max solar input."
The one-sentence version
Communications outage: ~300 Wh. Fridge outage: ~1,000 Wh. Multi-day outage: 2,000 Wh and up. And whatever you buy, insist on LiFePO4 chemistry and a surge rating above your biggest motor's startup spike.