Introduction to Electrical Units and Circuits

kW and kWh on your electricity bill

As your home uses electricity during the day, a meter spins (or digitally counts up) to record the amount of Real Power you use at all times. This measurement adds up to a certain number of kWh of energy consumption at the end of the month.

At the end of each billing cycle, the company “reads” your meter and records a total for energy usage. They then apply their fancy (and sometimes extremely complicated) calculations and bill you at a certain rate of cents per kWh.

Say you use 2,000 kWh per month, and your electric rate is $.15/kWh – your bill would be $300.00, plus any additional connection and service fees.

The cost of the electricity bill is calculated by multiplying the number of kWh that were consumed by the cost of 1kWh.

For example, the electricity bill’s cost for consumption of 900kWh per month with the cost of 10 cents for 1kWh is

900kWh x 10¢ = 9000¢ = 90$.


Watts, kilowatts and kilowatt-hours: power vs. energy

A watt is a measure of power, or the ability to do work. A watt-hour (wh) is a measure of energy. which means the amount of work done over a certain period of time.

A kilowatt (Kw) is simply a thousand watts and a kilowatt-hour (kwh) is a record of an average output of a thousand watts over an hour.

Another way to think about power and energy is as a marathon runner. Real Power (P) is like the ability to run at a certain pace, and the distance the runner covers is the amount of energy they use.


To find the kWh of 1,200 watts for 3 hours:

kWh = (1,200 × 3) ÷ 1,000

kWh = 3,600 ÷ 1,000 = 3.6

kWh to BTU, Joule conversion table

Kilowatt-hour (KWh) BTU IT Joule (J)
0.1 KWh 341.2142 BTU 3.6 × 105J
1 KWh 3412.1416 BTU 3.6 × 106J
5 KWh 17060.7081 BTU 1.8 × 106J
10 KWh 341214.1633 BTU 3.6 × 107J
50 KWh 170607.08165 BTU 1.8 × 107J
100 KWh 341214.1633 BTU 3.6 × 108J
500 KWh 1706070.8165 BTU 1.8 × 108J
1000 KWh 3412141.6331 BTU 3.6 × 109J
10000 KWh 34121416.3312 BTU 3.6 × 1010J

Kilowatt-hour definition

A Kilowatt-hour is an energy unit (symbol kWh or kWh). 1 kilowatt-hour is defined as the energy consumed by power consumption of 1kW during 1 hour:

1 kWh = 1kW × 1h

1 kilowatt-hour is equal to 3.6×106 joules:

1 kWh = 3.6×106 J

The energy E in kilowatt-hour (kWh) is equal to the Real power P in kilowatts (kW), times the time t in hours (h).

E(kWh) = P(kW) × t(h)


kWh meter

The kWh meter is the electric meter that measures the amount of electrical energy in kWh that is consumed in the house. The kWh meter has a counter display that counts units of kilowatt-hour (kWh). The energy consumption is calculated by calculating the difference of the counter’s reading in the specified period.

How many kilowatt-hour does a house use?

The energy consumption of a house is in the range of 150kWh..1500kWh per month or 5kWh to 50kWh per day.

It depends on the weather that affects the heating or air conditioning requirements and the number of people that live in the house.

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