Photovoltaic Calculator

Annual yield = System size in kWp × specific yield in kWh per kWp\nSelf-consumed electricity in kWh = Annual yield × self-consumption share\nFeed-in in kWh = Annual yield − self-consumed electricity\nGross annual benefit = (Self-consumed electricity × electricity price) + (Feed-in × feed-in tariff)\nNet annual benefit = Gross annual benefit − annual maintenance cost\nPayback period = Investment cost ÷ net annual benefit

Example: A 10 kWp PV system with a specific yield of 1,000 kWh per kWp produces 10,000 kWh per year. With a self-consumption share of 35%, 3,500 kWh are used on site and 6,500 kWh are fed into the grid. At an electricity price of €0.32 and a feed-in tariff of €0.08, the gross annual benefit is €1,640. With an investment cost of €16,000 and annual maintenance equal to 1% of the investment, net annual benefit is about €1,480. The rough payback period is around 10.8 years.

The calculator estimates annual solar yield, electricity used on site, electricity fed into the grid, annual financial benefit and a rough payback period. This allows you to compare different system sizes, price assumptions and self-consumption scenarios quickly.

It is primarily useful for homeowners and private users who want an initial estimate of whether a solar system could make economic sense. It can also help compare installer quotes or different planning assumptions.

The most important inputs are system size in kWp, specific annual yield and self-consumption share. Specific yield depends on location, roof pitch, orientation, shading and technical setup. Self-consumption often rises if electricity is used during the day or if a battery is installed.

The payback period shown here is only a rough estimate. Real-world economics also depend on installation cost, financing, insurance, maintenance, battery storage, tax treatment, feed-in conditions and future electricity price developments.

When comparing solar projects, do not focus on yield alone. Installation cost, self-consumption, roof orientation, shading, electricity prices, battery storage and your real household usage all influence whether the project is a good fit.

Electricity you use directly on site is often more valuable than electricity exported to the grid, because it replaces expensive retail electricity purchases. That is why a higher self-consumption share often improves project economics more than export volume alone. This becomes especially relevant for homes with daytime demand, heat pumps or EV charging.

A larger PV system can produce more electricity, but it also increases upfront cost. Good project economics depend on how well system size matches your consumption profile. That is why scenario comparison is so useful. You can test different kWp sizes, self-consumption assumptions and investment costs to see which setup looks most balanced.

This tool is meant as a first-pass economic estimate, not a complete investment model. It does not fully include financing, interest expense, insurance, module degradation, inverter replacement, tax effects, regional rules or detailed battery-storage economics. For a real decision, compare installer quotes and production estimates carefully.

A battery can increase self-consumption by shifting solar electricity into evening hours, but it also adds cost. That means a battery is not automatically the best economic choice. The key question is whether the added self-consumption benefit is large enough to justify the additional investment.

Many households choose solar not only for feed-in revenue, but also to reduce future electricity bills. The higher your retail electricity price and the more solar electricity you use yourself, the more valuable the system can become over time. That makes PV especially interesting for homes with significant daytime electricity demand.