There are two types of Underfloor Heating, one uses buried pipes which are fed with hot water from a Central Heating boiler, and the other is powered by Electricity. The Electric Underfloor Heating costs far more to run than one fueled by hot water from a domestic gas fired central heating system, and so it is the Electric Underfloor Heating Running costs which this article will focus on.
First of all, whilst Electricity is 100% Efficient (This means that it converts every bit of the energy it consumes from the mains into usable heat with no losses) it is also one of the most expensive ways of heating a home, and this also includes its use for underfloor heating. With an average unit price (KW/H) of Electricity hovering around 12p, Electricity is still far more expensive than Gas (3.5p) and even Heating Oil (6.5p) so even allowing for the lower efficiency and higher heat losses when using these fuels, they still remain a cheapest form of heating.
Unlike Storage Heaters, which use cheaper Economy 7 overnight Electricity to store the heat for later in the day, Electric Underfloor Heating has no heat storage facility, so Economy 7 isn’t really of any advantage for this type of heating (Unless you are awake all night!), so unless your house already uses Economy 7 for storage heaters, then switching to it purely for use with underfloor heating would be false economy, and will actually cost you far more than standard tariff energy.
Some houses, which are exclusively heated throughout with Underfloor heating as the Primary heat source will have an Economy 10 Tariff, but even with this (slightly!) cheaper rate, Underfloor heating will still remain far more expensive than other types of heating, so lets work out the figures in your own application.
First of all you need to know how much you currently pay for a unit (KWH) of Electricity, and this can be found on a copy of a current Electricity utility bill, then you also need to find out how much energy the underfloor heating consumes in each room, usually this is stated in Watts (W) or Kilowatts (KW) – one Kilowatt = 1000 watts.
If you do not know how much energy the underfloor heating consumes and it is not written anywhere, then the best method of finding out is to switch off all other appliances in the house and note the meter reading, then run the Electric Underfloor Heating for 1 hour on its maximum / high setting, and then note the meter reading after one hour of use, the difference between the start reading and end reading on the Electricity Meter will give a fairly accurate idea of how many KW the Underfloor Heating consumes.
For example, if the meter shows a 1 digit difference after 1 hour of use, then the underfloor heating consumes about 1kw (1000 watts), if it has used 2 units, then you would assume a consumption of 2kw (2000 watts) and so on. If the meter shows under 1 unit difference, or between 1 and 2 units then you should use the tenth digits on the meter to determine the fraction of a unit used. For example if the meter shows 7 tenths of a unit used then the consumption would be 0.7kw (700w), if the meter shows 4 tenths of a unit used, then 0.4kw (400w) and so on.
So, now you have the information on how much Electricity your Underfloor Heating consumes in a particular room, and also the cost of your Electricity, you can work out the running cost, and this is done using a simple formula.
PowerConsumption (in KW) x Electricity Cost (in pence)
So lets assume a room with Underfloor heating which consumes 1200 watts (1.2kw) the Formula would be used as follows
1.2 (kw) x 12p (Electricity unit cost) = 14.4p
So it would cost 14.4p per hour to run Underfloor Heating which consumes 1.2kw
The other disadvantage of Electric Underfloor Heating is the time it takes to heat a room, given it first needs to heat the surface of the floor, before heat from the floor eventually fills the room by convection, a lengthy two stage process which can take several hours in very cold weather, and for this reason many people leave the Underfloor Heating running continuously which can work out very expensive over a winter season, and is very wasteful especially if the room is unoccupied for long periods.
So in short, Electric Underfloor Heating can feel very pleasant and luxurious underfoot, but it can also be a very poor form of room heating – an expensive way of heating a room using an expensive fuel with which to do it!.
Often it is more efficient and cheaper, to simply keep the underfloor heating switched off, and use a portable Convector or Oil Filled Radiator to quickly heat the room, only during the periods where it is occupied rather than leave the Underfloor Heating on 24/7, even at low levels.
If Electric Heating is the only method of heating available to you, then you may also like to consider using a Portable Inverter Heater, which uses domestic heating oil and costs around 7p per hour to run.