To calculate your home's electrical load, identify all appliances and devices you use, note their wattage (found on labels or instruction manuals), determine how many run simultaneously during peak usage, and sum those watts together. This gives you the total load in watts; divide by 1,000 to convert to kilowatts (kW).
Start by making an inventory of major appliances: HVAC systems, water heaters, ranges, dryers, refrigerators, and lighting. Check the nameplate rating on each device—it typically lists watts or amps. For devices showing only amps, multiply amps × volts (usually 120V or 240V) to get watts.
Next, estimate simultaneous usage during your peak demand period (usually morning or evening). You won't run everything at once, so calculate realistic scenarios: morning scenario might include coffee maker, shower heater, and lights; evening scenario might add cooking appliances and entertainment devices.
For a rough estimate, multiply the sum of connected watts by a demand factor (typically 0.7–0.8) to account for the fact that not all devices run at full capacity simultaneously. This gives a more accurate peak load figure.
For precise calculations, especially if planning upgrades or new installations, consult your electric utility company—they often provide worksheets or guides. You can also review past electric bills, which sometimes show peak usage data. Professional electricians can perform detailed load calculations following the National Electrical Code (NEC) standards if needed for service upgrades or new construction.