"It's really a jungle," says Bengt Stridh, who is a university lecturer at Mälardalen University, where he researches and teaches about solar energy.

He is critical of how solar installers design their quotes today.

- It is very difficult for a consumer to compare quotes straight away, the thermology can be very complicated.

Bengt Stridh calls for both standardized quotations and for all companies to use the same reference values.

- It would greatly help the consumer, he tells SVT's consumer editorial Plus.

For those who are considering installing a solar system, an important first step is to compare quotes for equipment and installation from different companies. The companies' quotations are based on solar radiation calculations for one year.

Something that can complicate the comparison for consumers is that companies can freely choose what year they base their calculations on. If they choose a year of record-high solar radiation, the quotation can be very misleading.

According to Bengt Stridh, as a consumer, you should not just look at which company offers the highest impact in its offer. The risk, then, is that you choose what seems to produce the most - even though it may not be the best plant in your case at all.

Bengt Stridh thinks it is better to compare the cost per installed kilowatt hour (kWh) instead.

- That figure is easier to compare.

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Here you can follow the Plus editorial review of solar systems - and tip the editor!