Solar roofing costs: what does one investment in roofing and electricity cover?

All the required roof layers, however, remain in place.

This distinction matters when reading a cost estimate. The term ‘solar roof’ is sometimes also used for ordinary panels on mounting brackets. So ask which element drains the water and what would remain after the installation is dismantled. If a finished roof still lies beneath the modules, you are comparing a different way of carrying out the investment.

A new house allows the roof slope, cable routes and the work of the crews to be planned from the outset. The active section can have the same division lines as the elements without cells. As a result, the installation does not look like a later addition. It is also easier to agree the roof penetration points before the finished attic details are in place.

A similar opportunity arises when replacing a worn-out covering. The dismantling, preparation of the structure and new layers must then be calculated. If the roof is young and sound, the benefit of replacing the covering weakens. In that case, the calculation should take into account the value of material that could still serve for many years.

Photovoltaics does not replace thermal insulation. Above a heated attic, a correct layer arrangement and an airtightness solution are still required. The requirements for the membrane, support and ventilation derive from the chosen system. They cannot be removed from the cost estimate simply because the roof element produces electricity.

An inverter, protective devices, cables and commissioning of the installation are also needed. Add to that flashings, gutters and the execution of all details. A joint system organises these tasks, but does not make them cost-free. A good offer clearly shows which of them it covers and which remain the client’s responsibility.

Ask for two complete variants for the same area and a similar energy objective. The first should cover the integrated covering. The second an ordinary roof plus separate photovoltaics. Both must include similar scopes of work, roof access, equipment and acceptance procedures. Otherwise a lower price may mean only a shorter list of items.

Separate the cost of the active section from that of the passive area as well. Not every metre of roof slope has to generate energy. Some places are taken up by windows, flashings or shaded zones. Comparing the price per metre of the whole roof with the price per metre of the modules alone leads to a mistaken conclusion, even if both figures are true. In the cost estimate, also make sure that VAT is stated in the same form. A net amount from one offer and a gross amount from another are not comparable.

Generating energy is not the same as covering the whole of a home’s consumption. Production depends on light, the orientation of the roof slope and the temperature of the modules. Demand changes over the course of the day and the year. Some of the energy can be used immediately, some fed into the grid or directed to a suitably sized storage system.

Savings must therefore be calculated on the basis of the consumption profile, not just the annual total of kilowatt-hours. A house that is empty during the day may produce different results from a building where people work remotely. Integrating the modules into the roof does not in itself change the rules for billing energy or guarantee supply during a grid failure.

Prepare a drawing of the roof, its dimensions and its orientation relative to the cardinal points. Add photographs of the surroundings and information about chimneys and windows. Then collect electricity bills and plans for new consumers. A heat pump or an electric car may change demand, but they need separate consumption assumptions.

On that basis, a sensible active area and a realistic scope of work can be determined. The advantage of a joint solution is a coherent roof that also has an energy task from the outset. It is worth paying for that feature consciously. The final decision, however, should be justified by a complete design and a calculated cost, not by the slogan of two functions alone.

Among the manufacturers and brands of photovoltaic roofs are MDM NT (MyRoof), Wienerberger Wevolt, GAF Energy, SoliTek, Nelskamp, Electrotile, ML System, Solarstone, SolRoof and SunRoof.