Runtime by power station size: Chest freezer
| Power station size | Typical runtime | Realistic range |
|---|---|---|
| 300 Wh | 7 h 17 min | 5.1–10.2 h |
| 500 Wh | 12 h 9 min | 8.5–17.0 h |
| 1,000 Wh | 24 h 17 min | 17.0–34.0 h |
| 1,500 Wh | 36 h 26 min | 1.1–2.1 days |
| 2,000 Wh | 2.0 days (49 h) | 1.4–2.8 days |
| 3,000 Wh | 3.0 days (73 h) | 2.1–4.3 days |
Runtime by power station size: Upright freezer
| Power station size | Typical runtime | Realistic range |
|---|---|---|
| 300 Wh | 5 h 6 min | 3.6–7.3 h |
| 500 Wh | 8 h 30 min | 6.1–12.1 h |
| 1,000 Wh | 17 h | 12.1–24.3 h |
| 1,500 Wh | 25 h 30 min | 18.2–36.4 h |
| 2,000 Wh | 34 h | 1.0–2.0 days |
| 3,000 Wh | 2.1 days (51 h) | 1.5–3.0 days |
Why chest freezers are great in an outage
Cold air sinks. When you open an upright freezer, cold air spills out the bottom. Open a chest freezer and it stays put. Chest freezers also tend to have thick insulation and small compressors, which makes them among the most efficient appliances in a home: often 200–400 kWh a year.
A full chest freezer kept closed will typically keep food frozen for about 48 hours with no power at all (24 hours if half full). That means you don't have to run it non-stop: a few hours of power a day can be enough.
Run it in shifts
Running the freezer for 4–6 hours out of every 12 keeps it cold while using a fraction of the battery. If you have a fridge and freezer to keep cold, alternate between them. A freezer thermometer takes the guesswork out: keep it at 0°F (−18°C) or below.
Startup surge
Freezer compressors are small, but still surge to several hundred watts for a moment (around 600 W is typical). Most stations rated 600 W or more handle it. Some very small stations struggle, so test yours.
Work out your freezer's average
Take the yearly kWh from its EnergyGuide label, divide by 8,760 and multiply by 1,000. A 300 kWh/year freezer averages about 34 W. Put that in the calculator above, or add your fridge too in the runtime calculator.