What amount consists of one unit KWh

Electrical work W

If charge carriers with the amount of electricity Q are moved under the pressure of the electrical voltage U, work is done in the process. This is the electrical work that the utility companies pay for. What we mean by energy or electricity consumption is nothing more than electrical work.

Formula symbol

The symbol for electrical work is the capital W, which should not be confused with the unit of measurement for electrical power (watt).

Unit of measurement

The electrical work is specified in watt seconds (Ws) or often in kilowatt hours (kWh).

Calculation formulas

The electrical work W can be calculated with the amount of electricity Q and the electrical voltage U.

The amount of electricity Q consists of the electric current I and the time in seconds in which this current flows. The amount of electricity Q is given in the unit coulomb (C) or ampere second (As).

The electrical work W is typically a product of electrical voltage U, electrical current I and time t.

To simplify matters, the power P is calculated from the voltage U and the current I. The electrical work is then given in Ws or Wh. Often one also finds a multiple of this with kWh (kilowatt hour).

Because the electrical power is a product of the voltage U and the current I, the electrical work can also be combined with Ohm's law. The power P is therefore not necessarily required to calculate the electrical work. The only important thing is the time relationship with time t.

Relationship between electrical work and the price of electricity

The electricity supplier or electricity provider does not have the electricity or voltage paid for, but the electrical work. An electricity meter serves as a measuring device, which measures and displays the number of kilowatt hours (kWh) that are taken from the power grid.
More precisely, the electricity meter shows the electrical work (watt hours) caused by the active power (watts) over time (hours). Since several thousand watt hours accumulate very quickly, the unit of measurement is kilowatt hours (kWh).
The electricity costs are then calculated from the price per kilowatt hour (tariff) and the measured number of kilowatt hours consumed.

The tariff is inclusive of duties and taxes. In addition, electricity providers charge basic prices that were not taken into account in this calculation.

Example: Calculating the electricity price or calculating kilowatts (kWh)

One would like to know what kind of device causes electricity costs. It is important to know what power the electrical device nominally, i.e. in normal operation, consumes. Only a measurement with an ammeter can help here.
Then you still need the tariff price per kilowatt hour (kWh) from the electricity supplier.
We assume an alternating voltage of 230 V. If you need it exactly, you have to measure at the socket.

Voltage U:230 V_________ V
Current I:0.2 A_________ A
Time in hours:3 h_________ H
Tariff price:€ 0.14 / kWh_________ € / kWh


From the price of electricity, electricity consumption and the electricity bill

There is always talk of electricity price, electricity consumption and electricity bill. Every electronics technician knows, even if not consciously, that just as much current flows out of a circuit as it flows into. What else do we have Kirchhoff's rules for?
If you send electricity through a row of lamps, you will find that all lamps shine equally brightly. If, in theory, only one lamp consumed electricity, the other lamps would have to shine less brightly. But that's not how it works with electricity. And yet the term "power consumption" has spread in our everyday language.

The terms electricity price and electricity bill are also nice. No electricity is billed at all. The electricity bill says something about kWh, i.e. kilowatt hour, which corresponds to the converted power times an hour. Alternatively, one could speak of energy consumption, but that doesn't apply either. Energy can neither be consumed nor created.
The term "renewable energy" also invites you to smile. Sounds like the energy used can be recycled. Too bad that energy can only be converted into another form of energy.

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