Calculating your home's electricity load means adding up the power consumption of everything you use, which tells you your total demand (useful for sizing a generator, solar system, battery backup, or electrical panel). Here's a step-by-step approach:
1. List all your appliances and devices. Walk through your home and note every electrical item — refrigerator, HVAC system, water heater, lights, TV, microwave, washer/dryer, computers, chargers, etc.
2. Find the wattage of each item. Check the nameplate/label on the appliance (often on the back or bottom) or its manual — it usually lists watts (W) or volt-amps (VA). If only amps and volts are given, calculate watts using: Watts = Volts × Amps. If only kWh usage is shown on a smart plug or utility bill, that's energy over time rather than instantaneous load.
3. Distinguish running vs. starting (surge) wattage. Motor-driven appliances (refrigerators, air conditioners, well pumps, power tools) draw a brief surge — often 2–3 times their running wattage — when they start. This matters for sizing generators or inverters.
4. Add up running watts for total connected load. Sum the running wattage of everything that could be on at once (or realistically running simultaneously) to get your total load in watts.
5. Convert to kilowatts and estimate diversity/demand factor. Divide total watts by 1,000 for kW. Not everything runs at full capacity simultaneously, so utilities and electricians often apply a "demand factor" (a percentage reduction) to estimate realistic peak load rather than theoretical maximum.
6. Calculate daily/monthly energy use (kWh). For each device, multiply its wattage by the hours used per day, divide by 1,000, then sum across all devices for a daily kWh estimate; multiply by 30 for a monthly figure. Compare against your utility bill for validation.
For whole-house electrical panel sizing, licensed electricians use a standardized method outlined in the National Electrical Code (NEC Article 220), which accounts for square footage, appliance loads, and demand factors — this is more precise than DIY estimates and is required for permitted electrical work.