Electricity consumption of underfloor heating: how to correctly calculate and reduce costs

Heating the floor covering is a great idea, despite all its difficulties and disadvantages.The first thing you need to pay attention to when choosing a model is the electricity consumption of the heated floor. This determines whether such heating will be comfortable and economical at the same time.

Main types of electric heated floors

For home and residential premises, 4 types of heating devices are used:

1. Film graphite floors in the form of ready-made panels of film with a conductive coating.
2. Film resistive floors with metallized coating.
3. Cable heated floors in the form of ready-made multi-core sections.
4. Rod infrared floors.

From the point of view of financial costs, heating with electric heated floors is less profitable than when using built-in water systems connected to a gas boiler. In theory, using network gas is beneficial, even if you use an electric heated floor with a programmable thermostat. But in practice, not everything is so simple:

1. The costs of water heated floors are higher than those of cable or film models.
2. It is easier to manage energy consumption, which makes it possible to optimize costs.
3. Calculations show that the payback period for a water heated floor with a gas boiler is 5-7 years. Only in 8-9 years can we say that heating costs are minimized in comparison with the electric option.

Comparative analysis of the consumption of heated floors by type

Film heated floors are graphite strips sprayed onto a polymer base made from a mixture of terephthalate and polyethylene. There are options with a solid graphite field. Mat width – from 50 cm, 80 cm or 100 cm.

Per square meter there are from 100 W/h, 150 W/h, 220 W/h, 400 W/h. Special models can output from 400 to 800 W/h per 1 m². Maximum material heating temperature up to 50 ^OC, efficiency – 92%. Service life is up to 25 years, warranty on branded heated floors is up to 15 years. South Korean films from the HEAT PLUS company have a guaranteed service life of up to 50 years.

Resistive film floors differ from graphite floors in the material of the heat-generating layer. Typically it is aluminum sealed between two films of polyester. Power consumption – 140-150 W per square meter, maximum film heating temperature – 120 ^OC, working – 80 ^OWITH.

The film is quite capricious and is not suitable for any floor covering; efficiency is 89-90%.

A cable for underfloor heating has a heat dissipation of about 20 W per linear meter of wire length. The heater is sold in separate sections of 8 m, 12 m, 18 m, 22 m, 25 m, 50 m. The cable is laid in a snake on a substrate with clamps for pouring into a screed 3-5 cm thick. Heat generation power per square meter is 100-150 Tue Efficiency – 90%.

Rod heated floor – these are individual rods (rods) fixed to a polymer mat. Consumes 60-80 W/m². Warm floors are sold in ready-made strips, laid with a layer of glue before laying the tiles. Efficiency – 91-92%.

Calculation of electricity costs by type

To correctly assess future energy consumption, it is necessary to take into account the design features of the heating part of the heated floor.

The first factor affecting electricity consumption is the operating temperature and heating area of ​​the heated floor.

The lower the degree of heating of the electrical cable or film, the less loss from the heater into the environment - into the concrete base, wooden substrate or insulation layer.

In this sense, graphite films will be more efficient in terms of energy costs than cable heated floors. The highest costs will be for resistive models, since they are the hottest of all.

On the other hand, energy consumption is affected by the uniformity of floor heating. In this case, cable and rod floors look more attractive, since local overheated areas form on them during operation.

Heat transfer from a warm cable floor is higher, the air above the “hot lines” is heated more intensely. In addition to infrared heat transfer, air convection is more effective than radiation. As a result, the air in the room heats up faster, with less loss for the same energy consumption.

Only rod heated floors could be more efficient in terms of consumption, but their design involves installation under tiles or in a concrete screed. The energy consumption of a heated floor increases due to losses on the end (side) surfaces and through the rough base.

Energy costs depending on the finish coating

The most unsuccessful from the point of view of minimizing energy consumption can be considered wooden log floors and laminate. For conventional floorboards, electric heating of the base is practically not used due to the large thickness of the floorboards and the presence of an air gap between the finished floor and the rough filing.

In addition, a high-quality laminate must be laid on a shock-absorbing substrate made of pressed pine needles or polyethylene foam. Otherwise, the end locks on the slats will quickly break.

It is recommended to lay underfloor heating film mats under a leveling substrate. But because of this, heating efficiency decreases and energy consumption increases.

If you cover the warm floor with carpet or lay a carpet, then the energy consumption will only increase. Therefore, it makes sense to abandon traditional carpet products and use special underlays for laminate flooring to combat noise. They not only extend the “life” of heating films, but also reduce electricity consumption due to their good reflectivity.

In theory, the efficiency of cable heating systems under screed should be higher, if only because the tiles laid on top of them have approximately 2.5 times higher thermal conductivity than panels made of pressed paper.

But the lowest energy consumption for cable heated floors is shown by ordinary baseless linoleum glued to a cement-sand screed. In this case, the savings will be 15-20%. As soon as you replace the central heating system with a self-leveling self-leveling floor, energy consumption increases sharply to the level of film heaters.

Calculation of energy costs for electric floors depending on the type of room

The amount of electricity consumed by a heated floor is also affected by the type of room, as well as the characteristics of its use. The largest room in any house or apartment is the living room. Depending on the operating conditions, you can heat the floor surface that is not occupied by furniture. For example, in a living room with an area of ​​20 m² approximately 40% is occupied by furniture, including upholstered furniture. The remaining 60% (12m²) is occupied by laminate.

Film heated floors produced in South Korea will be used to heat them. Floor power per 1 m² – 220 W/h. To heat the living room in normal mode, 80 W/h is sufficient with a total consumption of 1600 W/h. In heating mode in the early morning or on cold days - 150-200 W/h, with a total consumption of 1.8-2 kW/h. It’s difficult to calculate exactly, but per month – up to 360 kW/h for an apartment 60 m².

A cable heater is used in the kitchen and hallway and is installed under the tiles over the entire surface. In addition to consumption (80-100 W/h is sufficient), the maximum heating temperature of the cable is important. It must be at least 80^OC for effective surface drying and room ventilation.

The same approach is used for bathroom and toilet. The only difference is that the cable heating is installed under the tiles in the free area of ​​the room. For example, you can make a path one mat wide (50 cm) from the door to the washbasin. Electricity consumption will be only 120-150 W/h, but, unlike other rooms, in this case the heated floor will work constantly.

A similar scheme is used for bedrooms and children's rooms, but based on graphite film floors. Electricity consumption in these rooms usually does not exceed 600-800 W/h.

How to reduce energy consumption

Electric heated floors have one drawback compared to water ones. When using film and cable heating, it is difficult to save energy.

With water, it is easier, for example, to heat the coolant in an electric boiler to pay for the night tariff, and use it for heating the rest of the time, and thereby reduce electricity costs.

For electric heated floors, there are several ways to save:

1. Programmable thermostat.
2. Thermal accumulator.
3. Zoning the heating system.

Proper zoning of heating system installation locations helps to reduce energy consumption. First of all, you need to avoid laying heated floor elements in drafts and under exhaust ventilation openings.

Thermostat and additional control sensors

Gives the best effect thermostat with program control. Modern models of thermostats (smart home system) are controlled by more complex programs that can monitor the air temperature outside and the degree of heating of the heated floor in the room using an infrared non-contact thermometer. In general, for an apartment or house, a “smart” thermostat can reduce consumption by another 15%.

It is believed that promising models of heat regulators with AI, which can download and analyze the weather forecast, will be able to adjust the operation of the heated floor in advance. How much exactly is difficult to say. It may be possible to reduce it by another 10%. Although the heated floor system itself will be expensive to maintain and set up.

Thermal storage

An easier way to reduce energy consumption is to use a concrete screed (slab) as a heat accumulator. But in order to get a positive effect, the base of the slab and the ends must be properly insulated with high-density foam plastic or penoplex with a thickness of at least 100 mm.

Heat accumulates during operation of a cable or, more often, resistive heater at night, when electricity consumption is charged at a reduced or preferential rate. Due to the large mass of concrete, heat is released evenly, within 5-6 hours, immediately after turning off the cable heating.Consumption savings with proper configuration can reach 15-18%.

New heating zoning principle

One of the ways to save heat is to lay film heaters not in the form of panels along the entire length of the room, but in squares (sections) of 25-50 cm. Each such section of the heated floor is connected with its own pair of wires to a programmable switch.

As a result, you can configure a dozen different floor heating schemes, in which only a small part of the room is heated. In general, the system turns out to be quite cumbersome, but not complicated. Electricity consumption can be reduced by 10-12%.

Reducing the consumption of heated floors is quite possible, but requires painstaking preparatory work at the stage of designing the base and laying the floor covering. If you combine several methods, you will be able to reduce heat loss by up to 20%.

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