Much has been made in the media about the rising gas and electricity prices, but have you ever stopped to wonder how much your hot water is costing you?

What hot water systems are available?

There are many ways to heat water, but most UK homes use the central heating system where the hot water is either held in a cistern or is heated by a combi boiler. Modern combi boiler systems are much more energy-efficient as they only heat the water when a hot tap is turned on.
Other methods to heat water in the home include kettles, electric power showers, electric heaters, solar powered systems and immersion heaters. Costs vary greatly as electric power showers start from around £100, while solar powered hot water systems can be more than £5,000 — which is a lot of hot water.

Combi boiler or hot water tank?

A regular boiler with a hot water tank is more efficient than a combi boiler at producing hot water, but then some heat is lost from the tank itself, so a combi may be more efficient overall.

Large households which use a lot of hot water could be better off with a regular boiler and tank, while smaller households should have a combi boiler, especially as they require less space. If you’re considering solar water heating, please note that many combi boilers are not compatible with this type of system.

How much does it cost to fill a hot water tank?

Hot water tanks come in many sizes, from 40 to 400 litres, while the hot water immersion heaters are normally either 3 or 6 Kilowatts (kW). To calculate how much a tank of hot water costs, you need to know your tank size in litres and the immersion heater power rating.

You can then work out your costs using numerous available online calculators. For example, on an average tariff, a 120-litre tank with a 3kW immersion heater will cost £1.02 to heat and take 125 minutes per tank. If your heater is 6kW, it will cost the same but take half the time. That amounts to £746.32 for the year.

How much does it cost to fill a bath?

Heating enough water to fill a bath is usually more expensive than a shower due to the amount of water used. You need to consider the temperature of the cold water entering the heating system, the temperature of the hot water and the cost per kWh of the energy. UK bath sizes are limited to 230 litres, but the average bath only contains around 80 litres.

Research has shown that heating enough water to fill an 80-litre bath costs around 50p using an electric immersion heater, compared to less than 20p for a modern combi boiler.

How much do I spend a year on hot water?

A typical household uses on average around 360 litres of water each day. About 20 per cent of a typical gas heated household’s heating bill is from heating the water for showers, baths and hot water from the tap. According to the Energy Saving Trust, this costs about £140 a year.

Depending on the size of your household, you could save money by installing a water meter.

Save money, save the planet

With the warming of the world’s climate, water conservation is one of the biggest challenges facing the world today. Saving water at home not only reduces your water bill, but it can also lower your energy bills as you use less hot water. You will also be doing your bit for your local environment and reducing your home’s carbon dioxide emissions.


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