- SI unit of power, equal to one joule per second
- named after James Watt, who improved the steam engine
- measures the rate of energy transfer or conversion
- 1 horsepower ~ 746 watts
- human basal metabolic rate: ~80 watts
- typical household light bulb: 10-100 watts
- Sun luminosity: 3.846e26 watts
- kilowatt (kW) for appliances, megawatt (MW) for power plants, gigawatt (GW) for national grids
- electrical power: P = volt times ampere (voltage times current)