# Calculating electricity prices

## Calculation Formula

```
Electricity bill = Power consumption (Wattage/watts) / 1000 * Hours of use (Hours) * Electricity rate per kWh (27 yen/kWh)
```

Only Watt is requisite, so find Watt anyway.

Note:

`Power consumption (Wattage/watts) = Pressure of the electricity (Voltage/volts) * Amount of electricity used (Ampere/amps)`

is also acceptable.- For kWh, the standard unit price for electric power consumption set by Home Electric Appliances Fair Trade Conference is 27 yen/kWh (from 2014), now became 31 yen/kWh in 2022. The culculation below is based on 27 yen/kWh.

## Example

### Question

We would like to know the electricity rate for one month when using Raspberry Pi 4 Model B as a server for 24 hours a day.

### Calculation

Since we could not find W, I substituted V and A for W. Say they are 5V, 2.5A each. Therefore, the formula is

```
Electricity bill = Power consumption (W) / 1000 * Hours of use(Hours) * Electricity charge per kWh (27 yen/kWh)
Electricity bill = {5(V) * 2.5(A)} / 1000 * {24(Hours) * 30(Days)} * 27 yen/kWh
Electricity bill = {12.5} / 1000 * {720} * 27 yen/kWh
Electricity bill = 243 yen
```

In reality, it depends on the configuration and operating conditions.