Buildings

Condensing Boiler Technology

In Europe, the main technologies used for room heating and domestic hot water supply are hydraulic heating systems with oil and gas central-heating boilers. Since the largest portion of energy is consumed by the generation of heat in buildings, the renovation of heating systems is one of the areas offering the greatest potential for savings. The German heating industry is at the forefront of efficient high-tech boiler development.

Low-temperature boilers, where the temperature of the water in the boiler is adjusted in line with the external temperature, set the standard for many years. Even with these boilers, the flue gas loss and standby loss were only between 10% and 12% of the effective heat energy.

The latest-generation boilers are called condensing boilers. These represent an enhancement of the lowtemperature boiler and reduce heat loss considerably. As a result, the amount of heat now released from the fuel is almost at the limit of what is physically possible. Condensing technology also utilises the condensation heat contained in the flue gas, which would otherwise remain unused. An additional increase in efficiency is achieved through lower flue gas temperatures, which means that even less heat is lost. As a result, condensing boilers can achieve efficiency values in excess of 98%.

Condensing boilers are cost-effective because the cost of purchase is recovered in terms of energy saved within just a few years. Replacing an outdated heating system, for example, with an oil condensing system in a single-family or two-family house in Germany costs, on average, € 8,000. At a heating oil price of € 1 per litre, a current annual heating oil consumption of, say, 4,500 litres (for heating and hot water) and a reduction in consumption of 30%, approximately € 1,350 can be shaved off the annual oil bill. This means that the cost of the condensing boiler system would be redeemed over approximately 6 years.