A watt-hour (Wh) is a unit of electrical energy equal to one watt of power consumed for one hour, forming the basis for kilowatt-hour calculations. While utilities primarily use kilowatt-hours (kWh) for billing, watt-hours measure smaller energy quantities in battery systems, portable equipment, and backup power supplies. One kilowatt-hour equals 1,000 watt-hours.
Technical Details
Battery storage systems commonly use watt-hour specifications: Tesla Powerwall stores 13.5 kWh (13,500 Wh), while portable power banks range from 100-500 Wh. A typical LED light bulb consumes 10 Wh per hour of operation. Energy calculations multiply watts by hours: a 5,000-watt HVAC system running 6 hours daily consumes 30,000 Wh or 30 kWh daily. Energy storage sizing requires understanding watt-hour capacity relative to daily consumption patterns.
Practical Significance
Watt-hours are essential for sizing backup power systems in critical HVAC applications. During power outages, understanding battery capacity in watt-hours determines how long equipment can operate: a 13.5 kWh battery powering a 1.5 kW air handler provides approximately 9 hours runtime. Solar installations paired with battery storage use watt-hour metrics to balance daily generation against consumption profiles, optimizing system performance and resilience for heating and cooling loads.