A kWh - What Does It Mean?

By Cormac Breen

Content Manager

A kilowatt-hour, or simply a kWh, is the unit of measurement used to calculate how much energy an electrical device uses and is based on how much energy is consumed by that device in an hour. It is the unit of measurement used by energy companies when calculating how much you need to pay on your electricity bill. The unit rate charged by an electricity company is the cost of 1 kWh.

What Is a Kilowatt-Hour?

A kilowatt-hour, kWh, is the unit of measurement used for electricity consumption, and it is what electricity suppliers use to calculate how much you have to pay on your electricity bills.

On the other hand, a kilowatt, kW is simply 1,000 watts and is a measure of power.

According to the Commission for Regulation of Utilities, CRU, the average Irish home consumes 4,200 kWh per year.

Some appliances use more kWh than others and are therefore more expensive to run. Below, you will find a table outlining the average cost per use of some common household appliances:

Prices based on Electric Ireland unit rate 35.83c per kWh on an Urban 24-hour meter with VAT included and 28% discount applied.
Last Updated: 09/08/2024

How Much Does a Kilowatt-Hour Cost?

How much a kWh costs is dependent on several factors, including:

1. Your energy provider
   Providers set their rates per kWh in accordance with the energy market, meaning they can rise and fall during the year.
2. Unit rate
   This is the price per kWh you consume, with different energy companies charging different rates.
3. Time of use
   If you have a smart tariff or a nightsaver the price per kWh changes throughout the day.
4. Discounts applied
   New customers are often placed on discounted rates, meaning you pay less per kWh than the standard rate for your first year of contract.

As of 2024, the average cost of one kWh on a standard rate in Ireland including VAT is 35.38 cents.

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How to Calculate the KWh of an Appliance

By knowing the kWh of common household appliances, you can work out which are costing you the most in terms of electricity consumption by applying the simple formula below,

First, we need to work out the kWh using the following formula:

Power rating (kW) × Time used (hours)

Electric Shower

Let’s take an average electric shower that has a power rating of 8,500 watts or 8.5kW as an example.

• The average household might use their shower for an estimated 10 minutes per day.
• By multiplying the shower’s kilowatt power rating (8.5kw) by the time spent using it (10 minutes).
• In this case, 8.5 × 0.1667 = 1.42 kilowatt-hours or kWh.
• We can now say that on average, the electric shower is using about 1.42 kWh per day.

Washing Machine

Or what about an average washing machine that has a power rating of 650 watts or 0.65kW as an example.

First, we need to work out the kWh using the following formula.

Power rating (kW) × Time used (hours)

• The average household might use their washing machine three times a week for an estimated 1 hour per cycle.
• By multiplying the washing machine’s kilowatt power rating (0.65kw) by the time spent using it (1 hour).
• In this case, 0.65 × 1 = 0.65 kilowatt-hours or kWh.
• We can now say that on average, the electric shower is using about 0.65 kWh per day or 1.95 per week (if the average is 3 cycles per week).

How To Calculate the Cost of an Appliance from Its Kwh Consumption

Now that we know how much energy each appliance is using, we can calculate how much it costs per day using the formula.

Energy usage (kWh) × Cost per kWh (€)

Electric Shower

• Take the daily usage of 1.42 kWh.
• Multiply 1.42 kWh by the cost of one kWh - in this case 35.38 cents.
• Which makes 1.42 kWh x 0.3538 cents = €0.50 per day.
• Or roughly €183 per year.

Washing Machine

We can also work out the average weekly cost of the washing machine using the same formula:

Energy usage (kWh) × Cost per kWh (€)

• Take the daily usage of 0.65 kWh.
• Multiply 0.65 kWh by the cost of one kWh - in this case 35.38 cents.
• Which makes 0.65 kWh x 0.3538 cents = €0.23 per day or €0.69 per week.
• Or roughly €36 per year (€0.69×52).

These are just examples, but it shows how the cost of using appliances, particularly high volume appliances such as showers, ovens, heaters etc., can add up over time.

By applying the simple formula above, you can calculate what devices in your house are costing you the most, and to make the necessary changes to how often you use them and lower your bills.

Saving Money on Your Electricity Bills with kWh

While it's somewhat unrealistic to expect the average household to track every singe kWh they use, by having an idea of your monthly or annual kWh usage, it can help you,

• ⚡ kWh and Saving Money on Electricity Bills
• Better calculate your energy consumption over different periods of the year and to make any necessary changes to your energy usage.
• Make more accurate price comparisons between energy providers specific to your needs and average energy usage, as energy providers advertise their tariffs as a cost per kWh.
• Be more energy efficient by knowing which household devices are costing you the most.
• Avoid overspending on your energy bills, as having some knowledge of kWh can help you better budget your monthly energy costs.
• Compare the different tariffs offered by an energy company, as they often vary from standard to time of use plans, and can be charged at a different cost per kWh.