Joule is a unit of energy, watt is a unit of power. Power is energy per time unit. In a way, those are incompatible units, but if you know in what time you spend a certain amount of Joule, you can convert to Watt, and vice versa. For example, if you use 200 Joule in 2 seconds, that is 200/2 = 100 Joule/second, or 100 Watts. Or, if a light-bulb uses 35 Watts, that is 35 Joules every second, so in an hour it will use 35 x 3600 = 126000 Joules, or 126 KJ.
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Watts is a unit of power; Joules is a unit of energy. Watts means Joules/second, so you would need to know how long a machine that uses 36 watts (for example, certain light-bulbs) is used.36 watts is simply 36 Joules per second; this is the same as 2160 Joules per minute, or 129,600 Joules per hour.Since the electricity bill is measured in kWh instead of Joule (1 kWh = 3,600,000 Ws = 3,600,000 Joule), you might also say that a device that uses 36 watts uses 0.036 kWh every hour.
Power is measured in watts, or joules per second. So in 90 seconds, 1200 joules of work is equal to 1200/90 watts or 13.3 watts.
Horsepower is a unit of power, but joules is a unit of energy. To convert horsepower to joules, you need an additional time parameter. One horsepower is about 745.7 watts. So a horsepower-hour is 745.7 watt-hours. One watt-hour is 3600 joules. A horsepower-hour is then 745.7 times 3600 = 2684520 joules.
It the unit is watts, megawatts is millions of watts, so to convert watts to megawatts, multiply the number of watts be 1,000,000.
Work is energy, measured in joules. The rate of work, or joules per second, is known as watts, or power.