Electrical load calculator: build an equipment inventory without guessing capacity

Start with equipment input ratings

The Electrical Load Calculator provides rows for EV charging, heating or cooling, water heating, cooking, laundry and other equipment. Enter the electrical input in watts using accessible nameplates or manufacturer information. A heating output in BTU per hour is not the same input quantity.

Keep unknown wattages blank. Use zero only when the equipment is absent or the particular row genuinely contributes no load. The calculator distinguishes missing information from zero and labels incomplete energy results as subtotals. Do not make a worksheet look complete by replacing every unknown with zero.

Understand the three different totals

Connected power is the sum of the entered wattages. Selected overlap is the sum of rows you mark as operating together. Daily energy multiplies each entered power by its operating hours and divides by 1,000 to produce kWh. These quantities answer different questions and should not be compared as if they were interchangeable.

For an illustrative pair, a 7,200 W charger used for two equivalent full-input hours contributes 14.4 kWh. A 1,000 W load used for three hours contributes 3 kWh. Connected power totals 8.2 kW; modeled daily energy totals 17.4 kWh. If only the charger is selected for overlap, that scenario is 7.2 kW.

References: U.S. EIA: Measuring electricity

Use operating hours carefully

Hours mean equivalent time at the entered input. Equipment that cycles or varies its power may use less energy than its nameplate rating multiplied by elapsed clock time. The worksheet does not simulate those controls. A household electricity bill or measured equipment data can help you recognize when an assumption needs refinement.

The optional rate field models a 30-day usage cost from the entered energy. It is not a complete bill forecast. If wattage or operating hours are missing, the displayed cost is a known subtotal and may substantially understate the complete scenario.

Take the inventory to a capacity review

An unchecked overlap box is a planning assumption, not a device that prevents equipment from operating. The tool does not apply code demand rules, evaluate starting current or phase balance, or inspect the service and feeder. Adding breaker handle ratings also does not supply those missing steps.

Use the inventory to explain planned appliances and open questions to the electrician. Keep equipment models, safe label photos and proposed locations with it. A professional review can then establish the applicable calculation and installation choices instead of treating the website total as permission to add a circuit.

Keep the next steps clear