Frequently asked questions

Yes. SolarSim is an independent calculation tool that helps citizens, businesses and municipalities assess whether solar panels are a good solution. We don't sell solar panels, don't broker offers, and receive no commission from suppliers.

Our only purpose is to provide a precise and objective calculation so you can make a well-informed decision, without commercial interests influencing the result.

We partner with municipalities to make the tool available free of charge, so more people get access to independent knowledge and can contribute to the green transition on an informed basis.

The battery size is calculated by comparing different solar solutions, both with and without a battery, to find the combination that best fits your consumption pattern.

Since batteries have a shorter lifetime than solar panels, expected replacement costs are also included in the calculation. It can be tempting to choose a large battery because it increases your ability to use your own electricity when the sun is not shining. But the extra cost of a large battery often does not pay for itself before it needs replacing. In many cases the calculation therefore shows that a smaller, cheaper battery is the most advantageous solution.

The system size is determined from your consumption profile, so the panels produce as much electricity as possible at the times you typically need it yourself. Covering your own consumption is worth more than selling surplus power, because you usually save more by using the electricity yourself than you are paid for selling it to the grid.

SolarSim simulates all realistic system configurations and calculates the solution with the best balance between energy production and financial return. That way you get a system that fits your consumption optimally.

The optimal orientation depends on your consumption pattern. SolarSim therefore calculates how the panels can best cover your electricity consumption throughout the day.

Using the electricity yourself is worth more than selling surplus to the grid, where the earnings are typically lower. In many cases the best solution can therefore be to also place panels facing east and west instead of only south.

In Denmark you currently cannot get the electricity tax refunded on EV charging if you have solar panels. The principle is that you cannot be refunded a tax you have not paid. Electricity from solar panels is exempt from electricity tax, so no refund is given.

Technically it is not possible to distinguish between electricity from the grid and electricity from the solar panels. As it stands today, EV owners with solar panels therefore lose the right to the refund entirely, even though part of the charging actually happens with electricity from the grid.

The government is working on a solution, however. From 1 January 2026, EV owners with solar panels are expected to qualify for a reduced electricity tax on charging. The scheme expires in 2030, and SolarSim's calculations therefore account for a reduced electricity tax in the period 2026–2030.

Yes. A green loan can be an attractive way to finance your solar system. These loans target energy improvements and are often offered on particularly favourable terms. The advantage is that the annual savings on your electricity bill can in many cases cover the loan costs, so the system effectively pays for itself.

Advantages of green financing:

Green loans often have lower interest rates than ordinary loans because they support sustainable investments. That means you pay less overall to borrow the money.

The alternative to borrowing is paying for the system in cash from your savings. With a green loan you can keep your savings and use them for other things, e.g. investments, enjoyment or as a financial buffer.

With the right loan terms, your monthly savings on the electricity bill can be higher than the loan payments. That gives a positive cash flow, meaning you can be ahead from day one.

You can get a tax deduction of up to 33.1% of the interest costs. That makes it cheaper to pay the interest on the loan (the deduction does not apply to the repayments themselves).

The payback period shows how long it takes before your solar investment has paid for itself through savings on the electricity bill. After this period, the system generates a financial surplus for the rest of its lifetime.

There is no single answer to what a "good" payback period is, because it depends on the system price, your consumption pattern and how you choose to finance the system.

Many choose a green loan, which often has lower interest rates than ordinary loans. That means your annual electricity savings can in many cases cover or even exceed the loan payments, so you can be ahead from day one without spending savings, which can be used for other things instead.

Another way to assess the investment is the internal rate of return (IRR), which shows your average annual return. It can be compared with, for example, historical stock-market returns, the difference is that solar panels provide a more stable and predictable return through electricity savings, while stocks typically fluctuate more with the possibility of higher returns.

Keep in mind that solar panels are a long-term investment. They are less liquid than stocks, but in return they contribute both financial savings and climate action.