Generator Sizing Tool

How to Use This Tool

NEC 2023 Article 220 Part IV — Optional Method

Step 1 — Home Size

Enter your conditioned square footage. The tool calculates general lighting at 3 VA/sq ft plus 4 small appliance circuits (6,000 VA) and one laundry circuit (1,500 VA).

Step 2 — Fixed Appliances

Enable each appliance present in your home. For appliances with a gas/electric choice, select the fuel type — gas appliances draw minimal electricity and are not counted. Use quantity selectors for refrigerators/freezers. If you have a range (combined unit), select Range only — do not also select Cooktop and Oven separately.

Step 3 — HVAC

Enable each A/C unit and select its tonnage (1,000 VA per ton). If you have electric heat (heat pump with backup strips), enable that unit's heat and select the strip size in kW — check your air handler nameplate for the heater kW rating. Gas heat draws only ~500 VA for the furnace controls/blower.

Step 4 — How the Calculation Works

Per NEC 220 Part IV Optional Method:

• All general/appliance loads are summed
• First 10,000 VA counted at 100%
• Remaining general loads counted at 40%
• All HVAC loads added at 100%
• Managed loads subtracted from total

Step 5 — Load Management

Select ALL loads in your home, then manage all loads you don't want included in the generator size. Managed loads are automatically shed by Generac Smart Management Modules (SMMs) when the generator reaches capacity, then reconnected when load drops. Typical managed loads: electric water heater, secondary A/C units, dryer, EV charger, pool pump.

The results show two recommendations — one for full load and one after removing managed loads.

Send Results to ReNew

We'll review your load calculation and follow up with a recommendation and quote.