Question

Electricity is billed in kilowatt-hours. Is this energy or power? How much is one kilowatt-hour in standard physics units? (The typical cost of one kilowatt-hour is 5 to 10 cents.)

Short answer

One kilowatt-hour in standard physics units is $3.6\times {10}^6\mathrm{J}.$

Step-by-step solution

Definition of one kilowatt-hour

1KWh is the unit of energy which is equivalent to the energy transferred or expended in one hour by one kilowatt of power.

Finding the energy

Kilowatt-hours is considered as energy, it can be expressed as$\mathrm{E}=\mathrm{P}\times \mathrm{T}$where, P is power and T is time.

When watts are multiplied by seconds, 1 kilowatt-hour can be translated to Joules in normal physics units. It can be stated as follows:

$$\begin{gathered} \mathrm{E}=\left(1\mathrm{kWh}\right)\left(\frac{1000\mathrm{W}}{1\mathrm{kWh}}\right)\left(\frac{60\min }{1\mathrm{hr}}\right)\left(\frac{60\mathrm{s}}{1\min }\right) \\ =3.6\times {10}^6\mathrm{J} \end{gathered}$$

Therefore, one kilowatt-hour in standard physics units is role="math" localid="1657787522533" $3.6\times {10}^6\mathrm{J}$.