The Appliance Runtime Matrix: Hours per Battery, for Everything

Every cell in the table below is computed, at build time, from the same spec registry that powers this site's sizing calculator — appliance draws from the Generac-format wattage worksheet, Kohler's sizing chart, DOE data, and manufacturer nameplates; battery specs from EcoFlow, Anker, Bluetti, and Tesla's published sheets. Nothing is estimated by feel, nothing is tested in my garage, and when a value is our documented assumption rather than a published figure, the methodology page says so.

Short version: runtime is usable watt-hours divided by duty-cycled draw — but only after the appliance passes two gates most lists never mention: the inverter's continuous rating and its start surge. The matrix applies all of it, for every pairing at once.

How to read the matrix

Three rules produce every cell. Average draw is running watts × duty cycle: a 700 W refrigerator whose compressor runs a third of the time averages 231 W, and a well pump that runs 3 minutes an hour averages 80 W — this is why "small" batteries post big hours on motor loads that rest. Usable capacity is 85% of nameplate for the plug-in systems (documented assumption for inverter losses and reserve; Tesla rates the Powerwall 3's 13.5 kWh on the AC side, so it counts in full). The gates come first: a load whose running draw exceeds the inverter's continuous rating shows ✗ exceeds inverter; one whose start demand exceeds the surge rating shows ✗ won't start — because kilowatt-hours are irrelevant if the motor never spins up. A dagger (†) marks a start that clears its gate by less than 10% — real-world voltage sag can erase margins that thin.

One honesty note on short-cycle loads (microwave, dishwasher, washer, dryer, range): their hours describe how long a battery sustains that usage pattern — a few runs a day — not one continuous run. And these are single-appliance hours; a real outage stacks loads, which is what the per-row "run it" links prefill the calculator to explore.

The matrix: 19 loads × 4 systems, base units

The pattern worth noticing: the column order is also a price ladder, and the failures cluster at the bottom of it. The Apex 300's 3,840 W inverter is why the big resistive loads — water heater, range, dryer — fail there and pass everywhere else. Meanwhile the duty-cycle column explains every "surprisingly long" number: a septic pump that runs 3 minutes an hour averages 54 W, so even the smallest base unit carries it for days. The fridge and the 1/2-hp sump pump are the two loads where the start-surge gate does real work — full walkthroughs in the refrigerator guide and the sump guide. (A CPAP is not in the registry — it's not a generator-sizing load — but it gets the same treatment in battery backup for a CPAP.)

Expansion scales the hours linearly

Every figure above is one base unit. Add battery modules and hours multiply by the capacity ratio — the appliance doesn't care how the watt-hours arrive:

Which size class you actually need — evening, overnight-to-a-day, or multi-day — is the whole subject of the home-backup power station guide.

Citing this table

The matrix is licensed CC BY 4.0: quote it, embed it, argue with it — with attribution and a link. Every row has a stable anchor (#refrigerator, #sump-pump-half-hp, and so on), each "run it" link opens the calculator prefilled with that load, and the underlying registry values carry named sources with access dates. If a spec sheet changes, the registry changes, and every cell on this page recomputes at the next build — which is the point: this table cannot drift from the calculator, because it is the calculator's data.

Where I land

Reference tables shouldn't editorialize much, so just this: the two most common sizing mistakes this matrix exists to catch are buying watt-hours when your problem is surge (the sump-pump column), and buying inverter headroom when your problem is watt-hours (the refrigerator column). Figure out which mistake you're about to make, then run your actual house through the calculator.