How generator load is modeled here
Estimate generator kW and kVA from running load, motor-starting demand, reserve, and power factor.
Use the Home Generator Size result as a load or layout note, then reconcile it with the complete circuit, panel, or equipment design.
Keep one unit basis for generator load from Total running load (W) through Generator power factor so conversions do not create quiet errors.
Use this page after the rough generator load scope is known. If the work is still being sketched, save the measurement basis and rerun the calculator once Total running load (W) is no longer a placeholder.
Final review notes
- Confirm Total running load (W) for generator load from the latest drawing, field measurement, or product schedule.
- Keep Largest motor running load (W) and Generator power factor tied to the same generator load scope revision before saving the result.
Editable values on this page in this Generator screening model
Document who supplied Total running load (W) and where Generator power factor came from before using the result outside the page.
- Total running load (W)
- Enter the finished Total running load (W) for the same generator load scope used by the remaining fields.
- Largest motor running load (W)
- Document where this generator load value came from if the result will be reused.
- Motor starting multiplier
- Use a project-specific value for Motor starting multiplier before relying on the generator load result.
- Design reserve (%)
- Keep this generator load Design reserve (%) visible as an assumption; it may matter more than the displayed rounding.
- Generator power factor
- Change this assumption when generator load conditions, product data, or risk tolerance changes.
Break irregular generator load work into separate runs when Total running load (W) or Largest motor running load (W) changes instead of averaging the conditions.
Use Circuit Load Calculator if the next decision needs to calculate demand-adjusted load on a modeled branch circuit.
Drawing checks before calculation
The Home Generator Size Calculator uses dedicated generatorSize inputs rather than a generic package or area substitute. Check each displayed generator load assumption against product data, field conditions, and the decision described in the result.
Resolve drawing and field conflicts around Total running load (W) for generator load before calculating; averaging them can make the estimate less useful.
Quantity questions
Should motor starting loads be included for generator load when the result looks low?
Include starting or inrush demand whenever motors, compressors, pumps, or other high-inrush equipment affect the selected equipment or circuit before carrying generator load forward. When Total running load (W) is estimated, mark the generator load result as provisional.
Which voltage should be entered for generator load for generator load planning?
Use the actual system voltage for the load being modeled, not a different nominal service voltage elsewhere in the building with Total running load (W) as the audit point.
The formula in plain terms in this Generator screening model
Use Total running load (W) and Generator power factor as the load basis, then check classification, diversity, protection, and voltage drop separately.
Check whether Total running load (W) and Largest motor running load (W) describe the same physical condition before trusting the generator load result.
The formula deliberately leaves judgment visible for this generator load scope. It converts the entered generator load assumptions, then lets you decide whether rounding, reserve, packaging, or review requirements should change the final use.
What the result supports for generator load
The generator load value should be reconciled with the load classification before it affects fixed wiring or equipment.
When generator load has repeated areas, calculate the unusual condition separately before adding it to the total.
Sample calculation
Default sample inputs: Total running load (W) = 6000, Largest motor running load (W) = 1500, and Motor starting multiplier = 3.
Estimated result: 13.5 kVA.
After changing Total running load (W), compare the new result with the sample so unexpected jumps are easier to spot.
Use the worked generator load line to verify units. After the sample makes sense, replace Total running load (W) and Generator power factor together so the result does not mix a sample quantity with a project-specific allowance.
What the result does not decide in this Generator screening model
Only the listed generator load inputs are included; pressure, elevation, diversity, friction, protection, grounding, and locally adopted requirements still need project review before purchase or construction.
Home Generator Size Calculator values are planning inputs, not conductor or protection selections. Electrical installation must follow the applicable code and qualified design for generator load.