⚡ Power Station Finder

Sizing a Power Station for Home Backup

Home backup sizing questions usually start in the wrong place — people ask 'how big a unit do I need?' before they've actually worked out what they're trying to run and for how long. Here's the order that actually gets you a right-sized answer.

  1. Start with capacity, but pick a real target
  2. Check surge, not just running watts, for anything with a motor
  3. Know whether you need 120V/240V split-phase output
  4. Decide if this is backup or primary power
Work through these in order — each step rules out a cause before the next one.

Step 1: Start with capacity, but pick a real target

This project's home-backup formula uses 3,000Wh as its 'full credit' target — enough for a fridge plus several other circuits through a full day-plus outage. That's a starting reference point, not a universal number: a smaller apartment (see the apartment-emergency use-case, targeting ~900Wh) or a full off-grid cabin (targeting the same 3,000Wh as home-backup, but for daily primary use rather than occasional backup) both need very different sizing logic.

Step 2: Check surge, not just running watts, for anything with a motor

A fridge compressor, sump pump, or AC unit all draw a brief startup spike well above their running wattage — see the dedicated surge vs continuous guide. Sizing on running watts alone is the single most common mistake in home-backup planning; a unit can look perfectly adequate on paper and still fail to start your fridge.

Step 3: Know whether you need 120V/240V split-phase output

Well pumps, electric dryers, and some HVAC systems need 240V split-phase power, not the standard 120V most power stations output. In researching this project's 20-entity dataset, only EcoFlow DELTA Pro 3 was explicitly confirmed to support this — and deliberately, no other entity was marked as supporting it without direct verification, rather than assuming a comparable flagship unit also has it. If your home has 240V appliances you need to back up, confirm this spec directly before buying, don't assume.

Step 4: Decide if this is backup or primary power

An occasional-outage home-backup setup and a true off-grid primary-power setup look superficially similar but should be sized very differently — see how the off-grid-cabin use-case weights solar input at 35% (the highest weight on this entire site) versus home-backup's 15%, because one of them has the grid as a fallback and the other doesn't.

Key Facts At a Glance

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