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As the construction of homes and villas in Sweden is increasing, the need for electricity will also increase. This leads us to develop new existing solutions to increase electricity production, at the same time we need to increase the use of renewable energy sources. To supply houses with sustainable and renewable energy sources, solar power is a good option to invest in.

The purpose of this work is to design a photovoltaic system on a villa. Our expectation after the design is to see how much the purchased share of electricity decreases. At the end of the project, we expect that this design can be used as a model for other similar villas, it is difficult to include all villas, considering how different conditions there are in Sweden.

The villa is in Hallstahammar and has an area of 138 m^2, and the roof area where solar cells are mounted is 84 m^2. The roof is facing southwest and has an azimuth of about 45°, which means that the sun shines on a large part of the roof. The villa has different roof slopes, at the garage and lower roof the slope is 20 ° and at the upper roof´s is 46 °.

The report answers the questions that arise during designing a photovoltaic system, as well as the villa's annual electricity consumption, and the facility's annual electricity production once it is installed. It is then analyzed whether the installation is profitable in terms of production cost and payback time. At the end of the report, it is more discussed challenges in solar cell design, such as shading and weather and their impact on the plant's electricity production.

To be able to answer the questions, various methods were used, including a literature study about solar cells to increase both interest and knowledge. The writers made saturations on the roof such as lengths, widths, and slopes. Thereafter, the simulation program PVGIS was used to calculate the plant's annual electricity production, and finally, calculations were performed to make financial calculations.

The results showed that the villa's electricity consumption in 2020 was 14,272 kWh and the electricity consumption was most during the winter period. The electricity cost during that year was SEK 21,140. The photovoltaic plant produces approximately 14,185 kWh per year and that production was highest during the summer period. The payback period for the plant was just over 9 years and the production cost was SEK 0.55 / kWh. Even though electricity production and electricity consumption did not match well and were efficient in different periods, the results still showed that the investment is profitable and provides a saving of SEK 629,000 over a lifespan of 30 years.