Is underfloor heating efficient?

The amount and type of energy your UFH uses will depend on the kind of system you have installed. There are two systems you can go for: wet and dry.

A wet system will work in a similar way to a radiator. Water is heated by your boiler or heat pump and pushed through pipes that have been laid under your floor. In contrast, a dry system uses electricity to heat wires. In both cases, a layer of screed is poured over the top to produce a flat surface for your flooring to be installed. This means that a wet system is heated via your current heating system (gas boiler, heat pump, etc.) and a dry system will use electricity, so each configuration could use different amounts of energy and will therefore vary in cost. Other factors are involved too, including the size of the room the UFH is installed in, the quality of your insulation and how high your ceilings are.

Because of these variables, it’s hard to determine how much energy UFH systems use.

For dry UFH, the power is specified in watts (W) per square metre (W/m2). This figure shows how much electricity will be used per hour if the system is left on all the time. A 100-150 W/m2 system should be more than sufficient for the modern average domestic family home. This means that the system uses up to around 150 W per one metre squared. If the UFH is only on for half the time, then half the electricity is being used. For example, if the system is running for 12 hours a day (and not 24), you’ll effectively be using around 75 W/m2. Therefore, a bedroom that is 12 m2 will use around 900 W (or 0.9 kW) per hour. This is based on your insulation being up to regulations with the correct floor insulation around the wiring too.

Wet UFH is powered by your central heating system, so the amount of energy it uses will depend on the size of your heating appliance. If your gas boiler is sized at 24 kW, it will use around 24 kW per hour. Therefore, if your boiler is on for five hours per day, it will use around 120 kWh. This will supply your whole home with heating and hot water, and not just the UFH.

Heat pumps are sized a little differently. They use a coefficient of performance (CoP) measurement that determines how much energy needs to be inputted to get a particular output. For example, a heat pump with a CoP of four can create four kW of heat from one kW of electricity. If the average household requires 12,000 kWh annually for heating, then a heat pump with a CoP of four will use around 3,000 kWh of electricity.

UFH will likely use less energy than standard radiators. This is because these systems are more efficient at circulating the heat around your home, and therefore they can run at a lower temperature. Whereas radiators may require the water to be heated to around 70 ℃, UFH can perform at temperatures as low as 30 ℃.

You may be surprised at the running costs of UFH.

For a 4 m2 bathroom requiring around 250 W to maintain the room temperature, this comes to 6000 Wh or 6 kWh per day.

For a dry, electric system with electricity charged at 15 p/kWh, it would cost around 90 pence to heat per day.

Alternatively with a wet system using gas at 4.5 p/kWh, the same room could be heated for 27 pence per day. Even better, a wet system using a heat pump with a CoP of 4.0 to heat the hot water, would reduce the cost to around 22.5 p per day.

To find out how many kWh you use per month or year, check your smart meter or gas bill.

These running costs will depend on the quality of the insulation in your home, how high your ceilings are, the temperature you want the room to reach and the amount of time you have your heating on for. 

You may have read about how to use your boiler efficiently, but where do you start when it comes to running your UFH efficiently? Pay attention to our tips below to help you keep the cost down over winter.