How to calculate the cost of household energy bills

The size of your property can have a big influence on the cost of your monthly energy bills. Generally speaking, the bigger the property, the more energy used, and the higher the bills.

For example, bigger homes need more energy for heating and cooling, and it’s also likely that there are more people living in them; you would expect a family of four to use more energy than a couple, for instance.

What size property do you live in?

As a general rule of thumb, these assumptions could be used to estimate energy consumption for different types of homes:

Flat/Apartment

• One or two bedrooms
• Occupants work or study full time
• No energy-consuming appliances like a tumble dryer or dishwasher

Terraced House

• Two or three bedrooms
• Occupants are a young family, using electricity throughout the day
• May sometimes use energy-consuming appliances

Semi-detached

• Three or four bedrooms
• Occupants are a family, using electricity throughout the day
• Frequently use energy-consuming appliances

Detached

• Four or more bedrooms
• Occupants are a large family, using energy throughout the day and evening
• Frequently use several energy-consuming appliances

But unfortunately, there isn’t a ‘one-size-fits-all’ formula to work out the average energy usage for each type of property. These examples may represent some households, but they’re certainly not accurate for everyone. This is because other factors such as lifestyle and habits have a big effect.

For example, what if a family of four living in a three bedroomed detached house are incredibly eco-conscious? They could, theoretically, use less energy than a couple living in a flat who leave the heating and the lights on 24/7.

How much energy do you use?

The energy regulator Ofgem has set out how to group households into high, medium and low energy users. This is a more accurate way to work out how much energy a household uses, rather than just looking at the type of property. Energy suppliers and comparison sites use these user groups for their quotes, and you can use them too to estimate your average bill costs.

Here’s what Ofgem suggests as annual energy consumption for each user group:

What is a ‘low energy user’?

• Uses 1,900 kWhs of electricity and 8,000 kWhs of gas in a year
• Lives in a small property, such as a one or two bedroom flat
• One to two people live in the property
• Occupiers are employed full time, and spend little time at home
• Typically uses the washing machine once a week, heating occasionally, no dishwasher or tumble dryer

What is a ‘medium energy user’?

• Uses 3,100 kWhs of electricity and 12,000kWhs of gas in a year
• Lives in a medium sized property, such as a three bedroom house
• Three to four people live in the property, for example two adults and two children
• Children at school and parents are at work during the day, with everyone home in the evening
• Typically use the washing machine a few times a week, have the heating on regularly, occasionally use the dishwasher, have TV and electrical appliances on in the evenings

What is a ‘high energy user’?

• Uses 4,600 kWhs of electricity and 17,000 kWhs of gas in a year
• Lives in a large property, such as a house with four or more bedrooms
• Four or five people live in the house (a large family or a group of housemates sharing)
• Occupiers could be at home during evenings and weekends, and sometimes during the day
• Typically use the washing machine most days, have the heating on regularly, use the dishwasher and tumble dryer regularly, and use several TVs and electrical appliances

So, our eco-conscious family of four could, in theory, be low or medium energy consumers, whilst the couple in the flat could have medium or high energy consumption. Taking into account your property type, family size, and your lifestyle is a much more accurate way of estimating the cost of your energy bills.

But, average bill costs also depend on how efficient your home is. No matter how careful you are when it comes to energy usage, if your house lacks good insulation, double glazing, and draught proofing, then you could be paying for more energy than you need. Find out how you could make your home more energy efficient.

If you’re not sure how much energy you use, installing a smart meter could help you to keep track. Or, use our running cost calculator to help you better understand your electricity usage.