Central heating

Central Heating - A central heating system is a heating setup in which a single heat generator supplies heat to all rooms in a building via a network of pipes. This distinguishes it from floor-by-floor heating systems, which serve only a single residential unit, and from individual room heaters such as wood-burning stoves or night storage heaters.

How It Works and Types of Fuel

The basic principle of central heating has been proven for decades: A central heat generator-the boiler or heat pump-heats a heat transfer medium, usually water, which is transported via a piping system to the radiators or underfloor heating in the individual rooms. The cooled water flows back to the heat generator via the return line. Modern systems use circulation pumps to drive the water circuit, as well as control technology that regulates the flow temperature and heating times according to demand.

Gas condensing technology was the standard in German residential buildings until a few years ago. Condensing boilers utilize the condensation heat contained in the exhaust gas and achieve efficiencies of up to 98 percent. However, since the Building Energy Act (GEG) 2024, new gas heating systems may only be installed in new development areas with municipal heat planning if they are powered by at least 65 percent renewable energy-for example, in combination with a solar thermal system.

Heat pumps extract heating energy from the ambient air, the ground, or groundwater and are considered a key technology in the heating transition. Air-to-water heat pumps are the most common type and achieve seasonal performance factors of 3.0 to 4.5-meaning that one kilowatt-hour of electricity yields three to four and a half kilowatt-hours of heat. Ground-source heat pumps with ground probes operate more efficiently but require drilling, which may require permits in densely built-up areas.

Pellet and wood chip heating systems burn renewable biomass and achieve near-carbon neutrality. However, they require a storage area for the fuel and regular maintenance of the burner and ash removal system. In rural areas of the metropolitan region where there is no gas connection, they represent an economical alternative.

District heating supplies buildings with heat from power plants or industrial waste heat via a municipal pipeline network. In Nuremberg, N-ERGIE operates a growing district heating network that primarily serves the city center, parts of Langwasser, and other neighborhoods. District heating automatically meets the GEG requirements, as it is predominantly generated from combined heat and power (CHP) in Nuremberg.

GEG Requirements and Replacement Obligations

The Building Energy Act requires owners to replace boilers that are more than 30 years old and operate using constant-temperature technology. Low-temperature and condensing boilers are exempt from this requirement. In the event of a change of ownership, the new owner must fulfill the replacement obligation within two years. Starting in 2024, the 65% renewable energy requirement will also apply to new heating systems in new development areas with municipal heat planning. For existing buildings, the new requirements will be phased in-in municipalities with over 100,000 residents by mid-2026 at the latest, and in smaller municipalities by mid-2028. Nuremberg has already initiated its municipal heating plan, so owners should familiarize themselves with the requirements early on.

Practical Tip for Nuremberg and Franconia

We recommend that owners in the Nuremberg metropolitan region first check whether a district heating connection is available or planned in the foreseeable future when planning a heating system replacement. N-ERGIE is continuously expanding its network, and a district heating connection eliminates the need to invest in a separate heat generator. If a district heating connection is not possible, an air-to-water heat pump is a good option in the region-the Franconian climate, with its moderate winter temperatures, enhances their efficiency. KfW subsidizes heating system replacements through the BEG individual measures with a grant of up to 70 percent of eligible costs, consisting of a basic subsidy, a climate speed bonus, and an income bonus. Prerequisites include the involvement of a certified energy consultant and submitting the application before work begins.

Frequently Asked Questions

Do I have to replace my old gas heating system immediately?

Functioning gas condensing boilers may continue to be operated-there is no immediate replacement requirement. The 30-year replacement requirement applies only to constant-temperature boilers, not to condensing or low-temperature units. If an existing gas heating system breaks down beyond repair, transition periods apply: Owners may install a temporary solution and have up to five years to install a GEG-compliant replacement heating system. We nevertheless recommend not postponing the replacement until a breakdown occurs, as subsidy conditions may deteriorate and a planned switch is significantly more cost-effective.

What does it cost to switch from a gas heating system to a heat pump?

The investment costs for an air-to-water heat pump, including installation, range from 25,000 to 40,000 euros for a single-family home. Additional costs may apply for adapting the radiators or installing underfloor heating if the existing flow temperatures are too high for efficient heat pump operation. After deducting the KfW subsidy, which can amount to up to 70 percent depending on the bonus combination, the out-of-pocket cost is significantly reduced. At current electricity and gas prices, the ongoing operating costs of a heat pump are generally lower than those of a gas heating system.

How do I find out if district heating is available for my building?

As a regional utility provider, N-ERGIE provides a map of the existing and planned district heating network in Nuremberg on its website. Alternatively, you can submit a request directly to N-ERGIE-checking for connection availability is usually free of charge. As part of its municipal heating plan, the City of Nuremberg will also publish which areas are to be supplied by district heating or hydrogen networks in the future. Property owners should wait for these planning results before making a long-term heating decision.

How does the type of heating system affect a property’s resale value and rentability?

The condition and type of central heating system have a direct impact on property value and rentability. A modern, GEG-compliant heating system-particularly a heat pump or a district heating connection-is increasingly becoming a deciding factor for buyers and tenants, as it promises low operating costs and long-term legal certainty. An outdated oil-fired heating system or a gas boiler at the end of its service life, on the other hand, deters buyers and often leads to price reductions that exceed the investment costs of replacing the heating system. Banks take the condition of the heating system into account when determining the mortgage lending value-a necessary heating system replacement can lower the mortgage lending value and thus worsen the loan terms. In the Nuremberg metropolitan area, we observe that properties with modern heating systems or district heating connections sell faster and command higher asking prices than comparable properties with outdated heating technology. Landlords also benefit from lower heating utility costs, which can be leveraged as a competitive advantage when seeking tenants. Early heating system modernization-before the next tenant change or sale-is therefore not only a legal requirement but also an economically sound measure.

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