Heating of Low-Energy Houses using electricity and gas – a comparison

A very frequent request from customers who are planning to build a detached house is for a comparison of the advantages of the individual heating systems available. The information presented here should help with the choice of heating system for their building. With regards to our area of focus at FENIX, the most frequent request is for a comparison between a warm-water system with a gas boiler and an electric direct heating system.

Two buildings, both low-energy detached houses, were chosen for comparison. The size of both of them is comparable, they are both "turn-key" homes from the same supplier, both of them stand in the same locality – near Opava in the Moravian-Silesian region – so are subject to the same climatic conditions, and both of them are used by three-member families at present. The first of them is completely heated by electric floor heating; the second has a warm-water system with a gas boiler.

Detached house in Hradec nad Moravicí – electric floor heating
The first house is located in the village of Hradec nad Moravicí. It is a detached house with no cellar, a saddle roof, a total built-on area of 71,7 m², and two floors with a total useable area of 113,8 m². Heating of the whole house is provided by floor heating which consists of Ecofloor heating cables. Detailed information about this house can be found in a separate article "A Low-Energy House in Hradec Moravicí "

Detached house in Nové Sedlice – warm-water system with a gas boiler
The second house is situated in the village of Nové Sedlice. The house is inhabited by a three-member family, and was finished and made ready for occupation in February 2004. It is a Z1-type house from the range offered by DK1 - detached houses by this company fulfill the criteria for placement in the NED (Low-Energy House) group.

Description of the building
It is a house with no cellar, with a saddle roof and a total built-on area of 72.9 m². Two floors provide a total area of 112.8 m² of useable (heated) area. On the ground floor there is a kitchen with a dining room, a living room, a bathroom and a study. On the first floor there is a bedroom, two rooms and a second bathroom.

• built-on area – 72,9 m²            
• useable (heated) area – 112,8 m²            
• calculated heat loss – 5,3 kW            
• main house circuit-breaker – 3 × 25 A            
• house tariff – D02

Heating
The heating system is the warm-water type with steel plate radiators. The heating elements are placed mainly under the windows, and the heating water distribution system is concealed within the structure of the building. The source of heat is a DAKON BEA 24 BT gas boiler of the type known as a "turbo" boiler (forced venting via the external wall), with a built-in warm-water storage heater. Regulation is provided by a Honeywell room thermostat, placed on the wall in the living room. Regulation of the system is supplemented by thermostatic heads on the heating elements. 

Acquisition cost
One of the advantages of electric heating is that there is no need to establish a gas distribution connection. Therefore, the acquisition costs for the heating of this house also include the cost of the connection of the building to the natural gas distribution system, as it is an essential part of the heating system.

• heating system (boiler, gas distribution system, heating elements, installation) 109.664,- CZK not including VAT      
• gas distribution connection (gas outlet, gas outlet box, ground works) 33.215,- CZK not including VAT      
• total – including 5% VAT 150.023,- CZK

Operational costs
As "other consumption" is also included in the cost of electric heating, the operational costs of this object contain the costs of both gas and electricity.

Comparison of the buildings

It is clear from the information provided that the acquisition costs for the electric floor heating were basically half of those for the typical warm-water system with radiators, even despite the fact that the detached house in Hradec nad Moravicí was built three years later. The cost of energy is then almost identical for both buildings; however, the gas heating system involves other expenditure in the form of regular reviews and service checks of the gas appliances which are not taken into account here.

Evaluation
Apart from the above-mentioned facts, there are other differences which are not necessarily apparent at first glance. In the first place, two completely different systems are being compared here, not only from the point of view of the energy sources used – typical convection heating is being compared with floor heating which is much more comfortable. Large-area systems feature better heat comfort and microclimate in the building – the distribution of temperatures is more even, there are no undesirable humidity fluctuations or dust circulation, and the interior area is not limited by radiators. For an appropriate comparison, the warm-water system in the "conventionally-heated" building should also be installed as a floor heating system – the acquisition costs would then increase by a further 60–80 thousand CZK.

Teoretické srovnání s alternativním řešením
At present, various systems with alternative sources of energy are very popular - heat pumps, or solar heating. For interest's sake, a theoretical comparison of electric floor heating with warm-water floor heating using a heat pump was carried out. As it is a simulation, the acquisition and operational costs of the system with a heat pump are just an estimate.
For gas heating, the cost of heating of the detached house in Nové Sedlice was 11 thousand CZK. If you estimate that the heat pump works with a coefficient of two (theoretically during the whole heating season), the cost of heating will be halved, which is approximately 5.000 CZK. Thanks to the low tariff, the payment for electricity will also be lower - originally 7 thousand CZK, now also approximately 5.000 CZK. It is 10.000 CZK/ year then.

From the theoretical comparison above it is obvious that even though the operational costs of the house with a heat pump are lower, the initial acquisition costs are so high that considering a theoretical saving of 8.000 CZK/year, the investment will pay back in as many as 26.5 years – which is more than the service life of the installed equipment.
Alternative sources certainly have their place in applications where a large amount of heat energy is needed – for example for the heating of a swimming pool – however, in typically-equipped detached houses of a size of up to 200 m² they are a non-returnable investment.

Conclusion
If we take into account the ratio of the acquisition costs and the operational costs, the initial investment returns as well as the degree of comfort which can be provided by the given systems, one can claim that large-area electric heating systems offer not only full value but in fact, are one of the most advantageous heating systems for structures which approximate or are in the NED (Low Energy Houses) category.