Watts are units of power. Power used over time is energy (which has units of “watt hours”). What’s the difference? Power is the rating for a device you use in your home (or a power plant). Energy is how much that device uses over time. So if you have a lightbulb that is rated at 10W and it’s on for two hours, that’s 20Wh of energy.
When talking about the power system these watt numbers get pretty big, pretty fast. Quick reminder about SI prefixes: kilo (as in kW) means one thousand, mega (as in MW) means one million, giga (GW) means one billion, and tera (TW) means one trillion. As a rough rule of thumb - your electricity bill gets measured in kW hours, a single generator has a power rating in MW, and all the electricity the US uses in a year in TW hours. More specifically, here are some things you’re familiar with and how many watts they are:
Thing | Watts |
laptop, while in use | 10 W |
indoor LED light bulb | 10 W |
indoor incandescent light bulb | 60 W |
one stove top burner or an air conditioner | 1500W |
one LED, running all year | 87.6 kWh |
a full charge of an electric car battery | 40 to 100 kWh |
average annual US residential electricity use per person | 4500 kWh |
modern solar farm | 4 MW |
modern wind turbine | 2 MW |
modern US wind farm | 90 MW |
coal power plant | 700 MW |
nuclear power plant | 1.5 GW |
US renewable capacity | 127 GW |
US coal capacity | 255 GW |
total US power plant capacity | 1.1 TW |
US renewable energy generation in a year | 372 TWh |
US total annual electricity use | 3860 TWh |
Sources for these numbers and more details can be found here.
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