Daily Power Consumption Calculator - Wh/Day | SolarRatio

Calculate your daily power consumption in watt-hours. Add appliances with wattage and usage hours to find total daily and monthly energy needs.

Accurately mapping your household or off-grid daily energy demand in watt-hours (Wh) is the foundation of every reliable solar system. This calculator turns appliance wattage and runtime into a single Wh/day number that drives panel sizing, battery bank capacity, inverter selection, and wire gauge. Skipping this step is the leading cause of undersized off-grid systems that crash on cloudy days, oversized arrays that waste capital, and battery banks that fail prematurely from chronic deep discharge. US households average roughly 30 kWh/day nationally, but an efficient off-grid cabin can run on 1,000–3,000 Wh/day — the gap highlights why a precise load audit matters before committing to panel and battery purchases.

How it Works

For each appliance, multiply rated wattage (W) by daily runtime hours to obtain its daily energy use (Wh/day). The tool sums all appliances to produce total daily Wh, then converts to monthly kWh by multiplying by 30. Inductive loads like refrigerators, freezers, and water pumps draw 3-7x their running wattage during startup surge — record both running and surge values when known. Include standby draw for TVs, modems, and chargers; a single 5 W standby load running 24 hours adds 120 Wh/day. For seasonal accuracy, build separate winter and summer profiles: HVAC, electric heaters, fans, and dehumidifiers shift the curve dramatically. The resulting total Wh/day becomes the input for panel-sizing (divide by PSH and efficiency) and battery-bank (multiply by autonomy days, divide by system voltage and DoD). For grid-tied US homes, this daily Wh figure also feeds the NEC 690 and NEC 705 interconnection calculations your AHJ (Authority Having Jurisdiction) inspector will review at permit.

Usage Scenarios

Off-grid cabin owners use this tool to confirm whether a 600 W array and 200 Ah LiFePO4 bank covers a fridge, LED lighting, water pump, and laptop without generator backup. RV and van-life builders calculate Wh/day for a 12V system powering a 12V compressor fridge, Maxxair fan, induction cooktop, and Starlink, then size the alternator-DC-DC charger accordingly. Emergency backup planners profile only critical loads — furnace blower, freezer, well pump, medical equipment — to determine the minimum battery and inverter required for a 24-72 hour outage. Tiny-home and ADU designers feed the result into NEC 690 service calculations to confirm code compliance and right-size the main breaker. A Texas hill country homesteader with a 1,200 Wh/day load profile can right-size a 400 W array and 200 Ah LiFePO4 bank, then claim the 30% federal ITC to cut net system cost before the first kilowatt-hour is generated. Marine and sailboat installations layer house loads with intermittent winch and anchor windlass surges to spec both house bank and starter isolation.