Shi - stock.adobe.comSolar thermal systems or heat pumps for hot water preparation lead to significant energy savings, especially in summer. Cost allocation is regulated by law: investment costs are not chargeable to tenants, and if a metering device is not installed, adjusted billing is necessary.
In a growing number of existing buildings, solar thermal systems or small heat pumps are supplementing the heating system for domestic hot water production. This leads to significant energy savings, particularly in summer, as the conventional oil- or gas-fired heating system can remain switched off. Studies show that solar thermal systems can save 30–40% of primary energy for hot water, depending on the region. Their use, along with that of additional heat pumps, requires an adjusted cost allocation.
Using such energy-saving technologies in your building reduces the energy consumption of the central heating system. Property managers and landlords then face the question of whether the costs for heat pumps or solar panels can be passed on to tenants.
Investment costs are not eligible for allocation.
According to the German Heating Costs Ordinance (Heizkostenverordnung), the investment costs of a solar thermal system or heat pump may not be passed on to tenants in the annual heating bill. Only the ongoing operating costs may be billed in this context. In the case of a retrofit, a rent increase is possible under certain circumstances (according to § 559 of the German Civil Code (BGB), formerly § 3, 1 of the Rent Control Act, or § 11 of the Second Ordinance on Calculation of Rent). For detailed information, it is recommended to consult the supplier of the heat pump or solar thermal system. Ongoing costs such as electricity for pumps and maintenance may, however, be billed annually; ideally, a separate electricity meter should be installed.
Heat inputs from earth, air, water and sun cannot be calculated for users.
Building owners are increasingly asking themselves what energy costs they can charge their tenants after installing a solar thermal system or heat pump. After all, tenants benefit from the lower energy consumption of the conventional heating system and could potentially offset this by paying a solar energy price. However, the legal situation is clear: the German Heating Costs Ordinance (Heizkostenverordnung) only permits the allocation of actual costs incurred and not the consideration of assumed cost savings. A solar energy price that can be charged to tenants does not exist.
This may seem unfair. Landlords can increase rents after installing energy-saving technologies, thus offsetting the investment. Furthermore, the building's value increases, improving its marketability and rental prospects.
contrastwerkstatt – stock.adobe.Heating bill from a professional
Brunata Minol supports you with digital measurement technology and radio transmission and in providing interim consumption information via app – secure, digital and compliant with the German Heating Cost Ordinance (HKVO).
Billing method when measuring equipment is missing
In the Heating Costs Ordinance (§ 9 para. 2) It is mandatory to record the heat consumption for hot water with a heat meter. If a heat pump or solar thermal system is also used to support hot water preparation, a second heat meter is required. If these meters are not present, a separate allocation formula is defined to calculate the share of hot water costs in the total total costs incurred.
This formula calculates the energy required for hot water based on the amount of water heated and its average temperature. However, the German Heating Costs Ordinance (Heizkostenverordnung) assumes conventional hot water heating solely by the central heating system. If, however, part of the heat is provided by a solar thermal system or heat pump, an adjustment is necessary.
- The electricity costs for the solar system or heat pump are recorded by a separate electricity meter and are only taken into account in the hot water costs.
- Since the German Heating Costs Ordinance (Heizkostenverordnung) does not contain a specific formula for the special case of heat pumps or solar thermal systems, an adjustment is made via the hot water temperature. In such cases, it has proven effective to reduce the hot water temperature in the formula to 40 °C, as this accounts for one-third of the heat generated by the heat pump or solar thermal system.
If this is not desired, the property manager or homeowner should specify an amount corresponding to the cost of hot water supplied by the central heating system. However, this is only possible if a heat meter is installed for hot water preparation and another one for the heating circuit.
Important notes
The described billing method applies only to the calculation of hot water costs if a solar thermal system or small heat pump is used to supplement the conventional heating system. If, however, the entire heating and hot water demand of a building is met by a larger heat pump, corresponding measurements of electricity consumption and heat input are necessary.
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