Power planning · 8 minute read

How to size backup power without buying too much

Start with the services your household must maintain, not a product page. Four simple numbers will eliminate most poor-fit options.

1. Define “essential” for one outage day

Make a short list: refrigeration, communication, lighting, medical equipment and any location-specific necessity. Leave comfort loads off the first pass. Check device labels or manufacturer documentation for running watts; motors may require higher startup power.

2. Estimate daily energy

This example is illustrative, not a promise of runtime. Actual consumption, conversion losses, temperature and battery age matter.

3. Separate capacity from output

Capacity, measured in watt-hours, describes stored energy. Output, measured in watts, describes how much equipment can run at once. A system needs enough of both. Check continuous and surge ratings against the loads you plan to connect.

4. Run a four-hour rehearsal

Before buying, simulate an outage safely. Track which devices you used, for how long, and what you missed. That small rehearsal usually produces a better shopping list than a broad emergency checklist.