The two numbers that matter
Capacity (Wh) tells you how long you can run a load — a 1,000Wh battery holds roughly enough energy to run a 100W device for 10 hours (minus some loss to the inverter). Continuous AC output (W) tells you what you can run at all — a unit rated for 300W continuous output simply can't start a 1,200W space heater, no matter how much energy is left in the battery.
The charts below assume 85% efficiency (typical loss through the inverter and cabling) and use three reference tiers that match popular Jackery and EcoFlow units: a 300Wh/300W entry unit, a 1,000Wh/800W mid-size unit, and a 2,000Wh/2,200W large unit. A dash (—) means that tier's output rating can't support that device at all.
Communication
| Device | 300Wh (300W) | 1,000Wh (800W) | 2,000Wh (2,200W) |
|---|---|---|---|
| 📱Smartphone (per charge)(15W) | ~16× | ~56× | ~115× |
| 📶WiFi router + modem(10W) | ~24h | ~85h | ~175h |
| 💻Laptop (per charge)(60W) | ~4× | ~14× | ~28× |
Lighting
| Device | 300Wh (300W) | 1,000Wh (800W) | 2,000Wh (2,200W) |
|---|---|---|---|
| 🏮LED lantern(5W) | ~49h | ~170h | ~345h |
| ✨String lights (20ft)(20W) | ~12h | ~43h | ~87h |
Kitchen
| Device | 300Wh (300W) | 1,000Wh (800W) | 2,000Wh (2,200W) |
|---|---|---|---|
| 🧊Mini fridge(60W) | ~4.1h | ~14h | ~29h |
| 🍽️Full-size fridge (avg draw)(150W) | ~1.6h | ~5.7h | ~12h |
| ☕Coffee maker (brewing)(800W) | — | ~1.1h | ~2.2h |
| ⏱️Microwave(1000W) | — | — | ~1.7h |
Medical
| Device | 300Wh (300W) | 1,000Wh (800W) | 2,000Wh (2,200W) |
|---|---|---|---|
| 😴CPAP machine(40W) | ~6.1h | ~21h | ~43h |
| 💊Nebulizer(100W) | ~2.4h | ~8.5h | ~17h |
Comfort
| Device | 300Wh (300W) | 1,000Wh (800W) | 2,000Wh (2,200W) |
|---|---|---|---|
| 🌀Box fan(45W) | ~5.4h | ~19h | ~39h |
| 📺43" LED TV(65W) | ~3.8h | ~13h | ~27h |
| 🔥Space heater(1500W) | — | — | ~1.2h |
| ❄️Window AC unit (small)(900W) | — | — | ~1.9h |
Tools
| Device | 300Wh (300W) | 1,000Wh (800W) | 2,000Wh (2,200W) |
|---|---|---|---|
| 🪚Circular saw (running)(1200W) | — | — | ~1.4h |
| 💧Sump pump (running)(800W) | — | ~1.1h | ~2.2h |
How to estimate your own device
Check the label or spec sheet on your device for its wattage (watts = volts × amps if only amps are listed). Then:
- 1Multiply the battery's rated Wh by ~0.85 to account for inverter loss — that's your usable energy.
- 2Divide usable Wh by the device's running watts to get hours of runtime.
- 3Confirm the device's watts is below the unit's continuous AC output rating, not just its capacity.
- 4For devices with a motor or compressor (fridges, ACs, pumps), expect a brief startup surge 2–3x higher than running watts — check the unit's surge rating too.
Recharging with solar
Pair any of these tiers with a 100–200W panel and expect a full recharge in 4–20+ hours of direct sun, depending on battery size. See our full solar backup power guide for recommended battery + panel kits, legal notes for states without a plug-in solar law, and setup steps.
Further reading