PowerCalcLab

Inverter calculator

Portable Power Station Size Calculator

Choose a station that passes energy, continuous-power and startup-surge requirements. A large Wh number does not guarantee enough output watts, and a powerful inverter does not guarantee enough runtime.

Advanced assumptions

Results update as you type. The calculator runs entirely in your browser — nothing you enter is sent anywhere.

Minimum rated capacity1,743 Wh

Calculation breakdown

Minimum continuous output1,000 W
Required startup surge1,600 W
Candidate energy checkPass
Candidate continuous checkPass
Candidate surge checkPass
Rated Wh = delivered Wh × energy margin ÷ output efficiency ÷ usable capacity ÷ health
= 1000 × 1.2 ÷ 0.85 ÷ 0.9 ÷ 0.9
= 1,743 Wh
  • Energy capacity, continuous output and surge output are independent requirements; all three candidate checks must pass.
  • Some boost modes reduce output voltage or are unsuitable for sensitive or motor loads. Use the normal rated and surge specifications unless the manufacturer confirms compatibility.

Method

How the number is reached

Delivered energy is increased by a design margin and then grossed up for output conversion, the usable share of rated capacity and end-of-design battery health.

Power is checked separately: simultaneous running watts receive a continuous margin, while surge is entered from appliance data or measurement and compared directly with the station's surge rating.

Rated Wh = delivered Wh × margin ÷ efficiency ÷ usable share ÷ health
Continuous W = simultaneous W × (1 + power margin)
Surge W = largest total startup requirement

Symbols

Wh
Energy capacity
W
Power at an instant

Worked examples

The same maths, applied

Example

1 kWh delivered-energy requirement

Use 20% energy margin, 85% output efficiency, 90% usable capacity and 90% end-of-design health, with an 800 W running and 1,600 W surge load.

Rated capacity = 1,000 × 1.20 ÷ 0.85 ÷ 0.90 ÷ 0.90 = 1,743 Wh
Continuous output = 800 × 1.25 = 1,000 W
Surge output = 1,600 W

Result: At least 1,743 Wh, 1,000 W continuous and 1,600 W surge.

Limits of the model

What it assumes, and where it stops

Assumptions

Delivered energy already represents the full task duration and the largest surge is known.

Not covered

Does not evaluate port-by-port limits, waveform, boost-mode behavior, charging time or pass-through operation.

Sources

Where these figures come from

  • DELTA 2 Portable Power Station — User ManualEcoFlowManufacturer specifications that keep rated battery capacity, continuous AC output, surge output and individual DC-port limits separate.
  • Inverter Smart — Technical specificationsVictron EnergyManufacturer ratings that distinguish continuous watts, continuous VA, temperature derating, peak power, maximum efficiency and zero-load consumption.
  • SI UnitsNIST Office of Weights and MeasuresDefinitions of the volt, ampere, watt and joule used for the unit conventions on this site.

Next steps

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Last meaningful update: 2026-08-19. This date changes only when the model, the sources or the guidance change.