How to plan a solar roof and heat pump together

A heat pump is not selected solely on the basis of the roof area available for cells.

Only after the heating demand has been determined can the appliance’s electricity consumption be estimated. The other consumers in the house are added to this value. The roof design should use these data but allow for their uncertainty. In a new building, actual consumption will also depend on the temperatures maintained by the occupants.

Over the course of a year, the roof may generate an amount of energy similar to the heat pump’s annual consumption. This does not mean that the appliance will run exclusively on this energy at every moment. Solar production is usually greater in the warmer part of the year. The demand for heating rises when the days are short and more often cloudy.

Summer surpluses and winter shortfalls must be accounted for in the adopted supply model. The house may still need energy from the grid. A zero bill should not be promised merely on the basis of matching two annual totals. Such a calculation ignores the hours of consumption, the billing conditions and the limitations of the appliances and any storage system.

Hot water preparation can partly take place during production hours. This requires a suitably sized storage tank and control in accordance with the heat pump’s instructions. It is not worth raising the temperature unnecessarily just to use up a surplus. A higher temperature can change the operating efficiency and the costs of the whole process.

In a building with suitable thermal inertia, small shifts in heating operation can be considered. These must preserve comfort and remain within the installation’s capabilities. Not every house allows the same scope of control. Good settings result from observing how the system operates, not from a single schedule copied from another building.

In a new house, the active area and the cable routing can be planned from the outset. Steel roof panels with a photovoltaic section then form a covering matched to the architecture. Instead of adding further elements above the roof slope later, the design covers the roof and the energy source from the beginning. This is an organisational and visual advantage.

This does not, however, automatically mean higher production than in every mounted installation. The yield depends on the module parameters, the arrangement on the roof slope and ventilation. When comparing variants, the complete system must be assessed. Aesthetic integration is a separate value, and operating efficiency should result from reliable calculations.

A storage system can shift part of production from daytime to evening hours. It is not, however, a simple way of preserving summer energy until winter. Its usable capacity, power and losses must match the consumers. A large momentary demand from the heat pump or heating element requires separate verification by the designer.

It is worth comparing two variants, with and without storage. Sometimes improving the house’s insulation or properly controlling hot water yields a greater effect first. The decision depends on the cost of the appliances and the usage profile. The mere fact of having a heat pump does not mean that storage is a mandatory or always the most cost-effective addition.

Provide the designers with the building data, the heating concept and the planned hot water consumption. Include the roof geometry and information about shading. Ask for monthly production and monthly demand to be shown. It is even better if the analysis takes account of the hourly profile and the actual possibilities for controlling the consumers.

After commissioning, compare measurements with the assumptions. Check the heat pump’s consumption, the temperatures and the amount of energy used on site. This allows settings to be improved without guesswork. The roof and the heat pump should support one goal, namely a reasonable operating cost for a comfortable home. Their cooperation requires good design and, later, calm observation of the results.

Examples of companies and brands in roof-integrated photovoltaics are ML System, SolRoof, MDM NT (MyRoof), SunRoof, SoliTek, Wienerberger Wevolt, Electrotile, Ennogie, Nelskamp and Terrán.