How to choose the power of HAKL TC 10 heating cable per m²
Why the correct power of the TC 10 cable is a key decision
When choosing a heating cable, most customers make one crucial mistake – they first consider the price or the length of the cable and only later find out whether the selected power actually corresponds to the area and purpose of the room. However, the correctly dimensioned power in relation to square meters is what determines whether the floor will be comfortably warm, whether the system will exceed the allowed temperature for the given floor covering, and, not least, how much the heating will actually cost in operation. An under-dimensioned cable will never achieve the desired comfort even when running at 100% power continuously, while an over-dimensioned cable will constantly cycle, which reduces the lifespan of the thermostat and in extreme cases can damage sensitive floor coverings such as laminate or vinyl.
The heating cable HAKL TC 10 is among the best-selling resistive cables on the Slovak market precisely because it is available in a wide range of power variants, which allows almost any area to be covered without unnecessary over-dimensioning. In this article, we will in detail explain how to calculate the power of the cable, what W/m² values are suitable for different types of rooms and floor coverings, and on practical examples we will show how to calculate the power yourself even before placing an order.
How the resistive heating cable HAKL TC 10 works
HAKL TC 10 is a single-core (in this version with two connecting ends, technically a two-core version with double connection) resistive heating cable intended for direct embedding in a concrete screed or in a self-leveling compound under tiles, stone, or under floating floors with appropriate thermal resistance. The cable works on a simple physical principle – electric current passing through resistive conductors is converted into heat, which is evenly transferred to the screed and then to the room space.
What does the designation "10" in the name TC 10 mean
The number 10 in the designation TC 10 refers to the linear (per meter) power of the cable – approximately 10 watts per meter of cable. This makes it easy to calculate backwards what length of cable you will get for a given total power. For example, a cable with a power of 1900 W has a real length of the heating part of approximately 190 meters, a cable with a power of 1030 W has approximately 103 meters. This property is also important when you need to check whether a cable with a given power will physically fit on the area you want to heat, at the chosen laying spacing.
Surface power (W/m²) – the basic parameter in selection
While the manufacturer specifies the total power of the cable in watts (e.g., 1030 W, 1100 W, 1900 W, 2200 W or 2410 W), another parameter is key for practical selection – the surface power per unit area, i.e., how many watts fall on one square meter of floor. This value varies depending on whether the cable serves as the only (main) heat source or only as additional surface heating alongside an existing radiator or other heating system.
Supplementary heating (surface heating)
If there is already another heat source installed in the room (radiator, warm air heating, air conditioning with heat pump function) and the cable is only to remove the feeling of cold floor underfoot, a surface power of approximately 80 to 110 W/m² is sufficient. Typically, this applies to living rooms, bedrooms, hallways or children's rooms, where the main goal is comfort, not heating the entire room.
Main room heating
If the cable is to function as the only heat source in the room (common in bathrooms, hallways, entrance halls or small kitchen areas without a radiator), a higher surface power is required, usually 130 to 180 W/m², depending on the room's heat losses, ceiling height, insulation quality and exterior wall.
Influence of floor covering on maximum power
The floor covering significantly affects what power can be safely installed. Tile and natural stone can withstand high surface power without risk of damage, while wooden and laminate floors have strict temperature limits (usually a maximum of 27–28 °C on the surface), so lower surface power and careful control with a floor thermostat with a temperature sensor is recommended under them.
| Type of covering | Recommended surface power | Note |
| Ceramic tile, stone | 130 – 180 W/m² | Suitable also as main heating |
| Large-format tile, marble | 140 – 170 W/m² | Fast heat transfer, even heating |
| Vinyl floors (LVT/click) | 90 – 110 W/m² | Check maximum temperature from the covering manufacturer |
| Laminate | 80 – 100 W/m² | Surface temperature sensor on the thermostat is required |
| Wooden floor (solid, parquet) | 70 – 90 W/m² | Consultation with the floor manufacturer is recommended |
Calculation: how many m² will a specific cable power cover
The practical calculation is simple – divide the total power of the cable (in watts) by the required surface power (W/m²) and you will get the area that the cable can cover. The formula looks like this:
Area (m²) = Cable power (W) ÷ Required surface power (W/m²)
Example: if you choose a cable with a power of 1900 W and want a surface power of 140 W/m², you calculate 1900 ÷ 140 = approximately 13.6 m². If you wanted to use the same cable only as supplementary heating with a surface power of 100 W/m², it would cover up to 19 m².
In the following table you will find an approximate conversion for all power variants of the HAKL TC 10 cable available in our range, calculated for three common scenarios – supplementary heating (100 W/m²), standard main heating (140 W/m²) and main heating with higher heat losses or under tile in a colder room (160 W/m²).
| Cable model | Cable length | Area at 100 W/m² | Area at 140 W/m² | Area at 160 W/m² |
| HAKL TC 10/ 1030 W | ~103 m | 10.3 m² | 7.4 m² | 6.4 m² |
| HAKL TC 10/ 1100 W | ~110 m | 11.0 m² | 7.9 m² | 6.9 m² |
| HAKL TC 10/ 1900 W | ~190 m | 19.0 m² | 13.6 m² | 11.9 m² |
| HAKL TC 10/ 2200 W | ~220 m | 22.0 m² | 15.7 m² | 13.8 m² |
| HAKL TC 10/ 2410 W | ~241 m | 24.1 m² | 17.2 m² | 15.1 m² |
Important note: the area values mentioned refer to the active heating area, i.e., the area where the cable is actually laid. This area does not include the space under the bath, shower area, built-in cabinets, kitchen line or other furniture without ventilation under the bottom – the cable is not laid there for safety and practical reasons. In practice, this means that the total floor area of the room (e.g., according to the area from the plan) is usually 10 to 25% larger than the actual active area on which the cable power is calculated.
Graph comparing power variants
The following graph simply illustrates what area each of the five power variants of the HAKL TC 10 cable can cover at a medium surface power of 140 W/m², which represents a common compromise between main and supplementary heating.
Cable layout on the surface and the effect of laying spacing
Surface power does not depend only on the total power of the cable, but also on the spacing at which you lay the cable on the surface. The denser (smaller spacing) you lay the cable, the higher the surface power per square meter you will achieve – logically because more meters of cable can fit into the same area. The cable is usually laid in a meandering pattern (snake-like, with regular turns), with the spacing between individual cable runs typically ranging between 6 and 15 cm depending on the required power.
A detailed step-by-step calculation of the required spacing according to the target power, including the exact formula for converting meters of cable to m², is covered separately in the topic dedicated to the cable laying spacing for TC 10 – we recommend reading it before the actual installation, as incorrect spacing is one of the most common causes of uneven floor heating.
Floor composition with heating cable
In order for the cable to transfer heat efficiently and safely, it must be placed in the correct floor composition. Missing or insufficient thermal insulation under the cable causes a large portion of the generated heat to escape downward into the ceiling structure instead of entering the room – this is one of the main reasons customers complain that the floor is not heating sufficiently, even with the correctly selected power.
The recommended thickness of the screed above the cable is usually 3 to 5 centimeters, and for tiling, a bonding or self-leveling screed with sufficient thermal conductivity is commonly used. The exact technological process of laying, securing with mounting strips or grids, and subsequent pouring can be found in separate topics – step-by-step installation of the TC 10 heating cable into the screed and how to properly secure and fix the TC 10 cable before pouring concrete.
Practical examples of calculation from everyday practice
Example 1: Small bathroom 4.5 m² as main heating
A bathroom with a floor plan of 2.25 × 2.2 m (total area approx. 5 m²), after subtracting the space under the bath and shower area, the active area is approximately 3.5 m². At a required surface power of 160 W/m² (bathrooms are more sensitive to cold, and tile can tolerate higher power), we need a cable with a power of approximately 560 W. The nearest available variant from below and above is HAKL TC 10/ 1030 W, which at this area achieves a surface power of up to 294 W/m² – which is too much and would lead to overheating and unnecessary costs. In such a case, it is more appropriate to choose a smaller laying spacing on a smaller area or reconsider whether the cable really needs to cover the entire active area, or alternatively choose another type of cable with lower power per meter, if available. Alternatively, the 1030 W power can be spread over a wider area including an adjacent hallway, if it is part of the same heating circuit.
Example 2: Kitchen 9 m² with supplementary heating
The kitchen has a radiator as the main heat source, and the cable is only to remove the cold from the floor. The active area after subtracting the kitchen worktop is approximately 6.5 m². At a target power of 100 W/m², we need approximately 650 W. The nearest suitable variant is HAKL TC 10/ 1030 W laid at a slightly larger spacing, which reduces the effective surface power to approximately 158 W/m² at an area of 6.5 m² – which is still high, so in practice, either the active area is increased (part under a low bar counter is included) to approx. 8-9 m², or the requirement is reduced and another power dimension is selected according to the actual available area.
Example 3: Living room 22 m² with supplementary heating
A spacious living room with a heat pump as the main heating source, the cable is used only for comfortable floor or vinyl floor surface heating. The active area after subtracting the seating and furniture along the walls is approximately 18 m². At a target power of 100 – 110 W/m², we need approximately 1800 – 2000 W. The ideal choice is HAKL TC 10/ 1900 W, which at 18 m² achieves a surface power of exactly 105.5 W/m² – which is exactly within the recommended range for supplementary heating under vinyl or laminate flooring.
Example 4: Corridor and entrance together 12 m² as main heating
An entrance without a radiator, tile floor, required surface power 150 W/m² due to frequent opening of the entrance doors and higher heat losses. Required power: 12 × 150 = 1800 W. The nearest option is again HAKL TC 10/ 1900 W, this time at a denser laying spacing achieving a surface power of 158 W/m², which is acceptable for a room with higher heat losses.
Step-by-step process of selecting power
To avoid getting lost in the selection, we recommend proceeding systematically according to the following steps, which are also summarized in the attached diagram.
What to do if the area does not match any model exactly
In practice, it rarely happens that the floor area matches one of the five available power variants exactly. In such cases, we recommend the following procedure, which has proven itself in dozens of customer projects:
- Prefer a slightly lower power over a higher one – if you are between two models, it is safer in the case of supplementary heating to choose the lower power to achieve even comfort across the entire area, rather than risking overheating on a smaller area.
- Adjust the laying spacing – within one cable, you can finely adjust the surface power by changing the spacing by a few centimeters (denser near the outer walls and cooler zones, sparser in the center of the room).
- Increase the active area – if the cable's higher power "exceeds" your needs, consider whether you could also cover an adjacent area (e.g., a hallway in front of the bathroom) within the same circuit.
- Allow for a reserve of 10-15 % – when calculating the required power, it is reasonable to allow for a slight reserve for extremely cold days, older buildings with poor insulation, or rooms with large glazed areas.
If you are considering whether the resistance cable type TC 10 is the most suitable solution for your project, or whether another type of heating cable (e.g., with a different power per meter or a different construction) would be better, we recommend reading the comparison in the topic HAKL TC 10 vs other resistance cables – differences and advantages.
Most common mistakes when selecting power
Over the years of sales and technical advice, we repeatedly encounter the same mistakes that lead to complaints or customer dissatisfaction:
- Calculating with the total room area instead of the active area – the result is an underdimensioned power, as the cable cannot fit on the actually available area with the recommended spacing.
- Ignoring the type of floor covering – using a high-power cable under sensitive laminate flooring without proper regulation can lead to its damage or deformation.
- Underestimating the thermal insulation under the cable – even a properly dimensioned cable will not work efficiently if the heat escapes downward instead of into the room.
- Confusing main and supplementary heating – the customer expects that a cable dimensioned for supplementary heating (100 W/m²) can heat the entire room without any other heat source, which is not realistic in the case of higher heat losses.
- Not allowing for a reserve for cold periods – calculating only for average temperatures without a reserve can mean insufficient comfort on freezing days.
Further expansion of this topic, including specific mistakes during the installation itself, can be found in the article most common mistakes during the installation of resistance cables TC 10.
How power relates to cable functionality testing
Regardless of which power you ultimately choose, it is essential to measure the cable resistance with a multimeter before and after embedding it in the screed and compare the measured values with the manufacturer's data on the cable label. The cable resistance is directly related to its power (according to Ohm's law), so a significant deviation from the stated value may indicate cable damage even before it is embedded, when repair or replacement is much simpler and cheaper. The exact measurement procedure and acceptable deviations can be found in the topic how to test the functionality of the TC 10 cable before and after embedding in the screed.
Lifespan and reliability with the correctly selected power
A properly dimensioned cable that does not operate at the limit of its capabilities and is not forced to run continuously at 100 % power due to underdimensioning has a significantly longer lifespan. HAKL TC 10 resistance cables are designed for decades of operation without the need for intervention when installed and dimensioned correctly, as practically no mechanical wear occurs after embedding in the screed. More on how to extend the system's lifespan and what to pay attention to during long-term operation can be found in the topic maintenance and lifespan of resistance heating cables TC 10.
Frequently asked questions about selecting the power of the HAKL TC 10 cable
Is it better to choose a higher power "just in case"?
No, an overdimensioned cable will cycle more frequently (turning on and off), which increases the wear of the thermostat and can lead to an uneven, "wavy" feeling of heat on the floor. In addition, with more sensitive floor coverings, there is a risk of exceeding the maximum allowable surface temperature. It is always better to calculate precisely according to the actual active area and the purpose of heating.
Can I use the TC 10 cable as the only heat source in the entire apartment?
Theoretically yes, but in practice, this is only recommended for well-insulated new buildings with low heat losses. In older or poorly insulated apartments and houses, it is more suitable to combine floor heating with another main heat source and use the cable rather for supplementary heating or only in individual rooms such as the bathroom.
How do I determine the exact active area in my room?
Measure the total floor area of the room and subtract the area under built-in furniture, kitchen units, the bathtub, the shower area, and other fixed elements where the cable is not laid. You will usually get an active area that is 10 to 25 % smaller than the total area of the room.
Can the cable power be changed after embedding?
No, the cable power is fixed by its construction and length and cannot be changed after embedding in the screed. Only the room temperature regulation can be adjusted afterward by setting the thermostat, not by changing the cable power itself. Therefore, it is important to do the calculation thoroughly before purchasing.
What if none of the offered power options exactly match my area?
Select the nearest lower power variant and fine-tune the surface power by slightly adjusting the cable laying spacing in the given area. Alternatively, you can consider expanding the heated area to an adjacent space within the same circuit, if the room layout allows it.
Does ceiling height or window size affect the required power?
Yes, rooms with high ceilings, large glazed areas, or an outer wall facing north have higher heat losses, so it is recommended to choose the upper end of the recommended power range for such rooms, or even add a 10–15 % reserve to the calculated power.
Conclusion
Selecting the correct power for the HAKL TC 10 heating cable is not complicated mathematics, but it does require a careful approach – from accurately measuring the active area, through determining whether it will be main or supplementary heating, to considering the type of floor covering and heat losses in the room. Thanks to the wide range of power variants, such as 1030 W, 1100 W, 1900 W, 2200 W, and 2410 W, it is possible to cover almost any standard area in a household without unnecessary overdimensioning or, conversely, insufficient power. If you are unsure about the calculation, or your area does not exactly match any of the available models, do not hesitate to contact us – we will gladly help you with precise dimensioning based on the actual layout of your room and the planned floor covering.
Do you have a question about this topic?
Are you unsure or dealing with a specific situation in your home? Write to us – we are happy to help.