Power is the rate at which energy is transferred, or the rate at which work is done. It tells you how quickly something transfers energy, not how much energy it transfers in total. Power is measured in watts (W). An energy transfer of 1 joule per second is a power of 1 watt.
There are two equations, and they are the same idea because doing work is a way of transferring energy. Power P = E ÷ t, where E is the energy transferred in joules (J) and t is the time in seconds (s). Also P = W ÷ t, where W is the work done in joules. For example, a motor that transfers 3000 J in 60 s has a power of 3000 ÷ 60 = 50 W.
You can rearrange the equation to find the energy: E = P × time. A kettle with a power of 2000 W that runs for 30 s transfers 2000 × 30 = 60000 J.
Power lets us compare machines. Imagine two electric motors that lift the same weight through the same height. They do the same amount of work. The motor that does it in less time has the greater power. A more powerful machine is not one that does more work in total, but one that does the work faster.