# How much energy is 2100 watts

### Kilowatt hour (kWh)

This is a unit for Amount of energy. Kilo-watt-hour (kWh) means "1000 watts during one hour". This corresponds, for example, to the electrical energy that ten switched on 100 W lightbulbs consume for one hour. Or twenty 10 W LED lamps that produce just as much light - but for 5 hours.

In Switzerland, one kWh of electricity costs between 10 and 40 centimes, depending on the region and the tariff chosen (night tariff, green electricity ...).

Good to know: kWh is also used for other forms of energy than electricity. One liter of heating oil, for example, corresponds to 10 kWh, one kilo of wood: 4 kWh.

### The annual consumption of a deviceor calculate a lamp

To calculate the amount of energy that an electrical installation consumes in a year, you only need to multiply the power (in watts) by the number of operating hours. For example, a living room halogen lamp with 250 watts that is used 3 hours a day for 300 days a year (days of absence are not counted):

250 W x 3h x 300 (days) = 225,000 Wh, results in 225 kWh. If the kWh costs 25 cents, the electricity costs for the lamp amount to CHF 56 per year.

Another example of a 50 watt aquarium filter pump that runs continuously:

50 W x 24h x 365 (days) = 438,000 Wh, results in 438 kWh. At 25 cents per kWh, the pump costs CHF 109 per year.

### kWh and CO2

Consuming electricity means CO2 release into the atmosphere. The amount of this gas released per kWh depends on how the electricity is produced. That is why one kWh of electricity generated in a coal-fired power plant emits more than one kilo of CO2. One kWh from a hydropower plant, on the other hand, releases less than 50 grams of CO2 into the environment (the CO2that is released for the construction and maintenance of the infrastructures is included). Since most countries have several power sources, one speaks of the "energy mix" to reduce the CO2-Estimate the amount released per kWh.