A Kwh - What Does It Mean?

A kilowatt-hour, or more commonly abbreviated as simply 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 also the unit of measurement used by energy companies when calculating how much you need to pay on your electricity bill. Knowing more about what a kWh is can also help you save money on your electricity bills.

What Is a kilowatt? Is It Different to a Watt?

All electrical devices and household appliances consume electricity measured in watts (W). As most appliances use at least 1,000 watts, it is more common to use kilowatts (kW's) rather than watts when measuring electrical consumption. Simply put, a kilowatt (kW) describes how much energy an electrical appliance uses and is a measurement of power equal to 1,000 watts

So What Is a Kilowatt-Hour?

A kilowatt-hour is the unit of measurement used when measuring electricity usage. It is based on the amount of energy consumed in one hour by a 1,000 watt electrical appliance Some household appliances consume more energy than others, meaning that they consume far more electricity in a standard kilowatt-hour.

How Much Does a Kilowatt-Hour Cost?

As of 2024, the average cost of one kWh on a standard rate in Ireland including VAT is 35.38 cents. This is the figure used by energy providers to calculate your monthly bill.

There are other factors that can affect the total amount you pay on your energy bill. However, other elements such as the specific tariff you are on, any discounts applied, or if you have a flexible plan that includes daytime and nighttime rates.

Below you will find some examples of the estimated cost of running some common household appliances based on the average cost of a kWh.

How to Calculate KWh

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 Based on 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 washine 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.

Does Knowing about Kwh Help You Save Money on Your Electricity Bills?

Yes! By having an idea of your monthly or annual kWh usage it can help you,

• Better calculate your energy consumption over different periods of the year whether that be monthly, seasonally, or annually and to make any necessary changes to your energy usage
• Make more accurate comparisons between energy providers specific to your needs and average energy usage as energy providers advertise their tariffs as a cost per kWh
• Compare the different tariffs offered by an energy company as they often vary from flexible to fixed term plans, and can be charged at a different 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

Interested in making savings on your energy provider? Browse our energy suppliers pages to see who has the best kWh rate for your home and energy needs. Selectra’s dedicated team of sales representatives are on hand to answer all of your questions in relation to home energy providers and are ready to help you make the best decision for you when it comes to choosing your energy provider.