Inverter Generator Load Calculator
What this calculator measures
Apply a documented site-retention factor and an explicitly retained reserve to continuous real-power watts. Use 100% site retention if the entered rating already includes site conditions. Startup and connection limits remain separate.
Inputs and units
Use readings and ratings that describe the same equipment, operating interval, and measurement boundary. The sample entries are editable examples; they do not establish the specifications of your generator.
| Input | Example entry or choice |
|---|---|
| Applicable continuous running rating (W) | 3000 — enter a documented value |
| Documented site output retained (%) | 100 — enter a documented value |
| Available capacity held unused (%) | 20 — enter a documented value |
Calculation method
First apply the documented fraction of continuous output retained at the site. Then hold the selected fraction of that available capacity unused. Planning running watts = continuous rated W × site retention × (1 − retained reserve).
Worked example
A 3,000 W continuous rating with a documented 90% site factor is 2,700 W available. Holding 20% of that unused leaves a 2,160 W running-load allowance. This retained-reserve convention differs from adding 20% to a load.
Limitations and checks
The tool does not infer a manufacturer derating curve from a generic altitude or temperature rule. It also does not replace a motor-start test or the generator current, receptacle, and voltage limits. If the entered rating is already the applicable site rating, leave site retention at 100% to avoid double derating.
For a practical decision, keep the original readings, the generator model, the relevant manual or specification, and the assumptions alongside the result. A different load, site condition, rating basis, or unit convention can answer a different question even when the arithmetic is correct.
Sources and methodology
Publisher: CSP Digital Media Ltd. To report a formula, unit, or example error, contact us with the tool name, inputs, displayed result, and expected calculation.