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Sizing Calculator

Add your appliances, set usage hours, and get a precise watt-hour target — plus model recommendations that fit your needs and budget.

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How the math works

Daily Wh = Sum of (watts × hours/day) for each appliance. Peak continuous wattage = sum of all appliances running simultaneously.

We apply an 85% usable depth-of-discharge (DoD) assumption — most LFP batteries can safely use ~85% of rated capacity before impacting cycle life. Then we add a 20% headroom buffer for inverter efficiency losses, temperature derating, and real-world variation. Formula: Required capacity = (Daily Wh ÷ 0.85) × 1.20.

Surge note: Compressors, motors, and pumps draw 2–7× their running wattage for 1–3 seconds on startup. We flag any appliance whose estimated surge may exceed common continuous output limits. Confirm surge specs before purchase.

Methodology is for estimation only. No first-hand testing was performed on any specific unit. Always verify rated capacity, DoD, and surge ratings in the manufacturer's specifications.

Buyer's Guide
Buying for home backup?
Read our full guide — top picks, LFP vs NMC explained, and direct links to buy from EcoFlow, Bluetti, and Jackery.
Read the full buyer's guide →
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