Our Eco House blog

Alright, you’d like to buy a photovoltaic panel or even several of them to reduce your electricity bill and to lower pressure on the environment but where to start?

First, you should decide how powerful panel you need. Let’s say that you need to power 100W appliance. If you buy a 100W panel will it really deliver 100W? Actually, it’s a bit more complicated. Solar radiation varies from place to place, fluctuate under different weather conditions, etc.

It was necessary to create a standard how to label photovoltaic panels and it was agreed that their output will be measured under these conditions:

• power density (amount of solar radiation) of 1000W per square meter
• temperature of the module or the cell is 25 °C

How can you find out how much solar radiation your area receive? There are maps which will show the average annual solar radiation. Below is a map of Europe.

From the map you can easily find out the 100W panel will produce around 200W in the South of Spain but only around 60W in the Iceland if the panel is facing South and is under the right angle.

Also check how efficient the solar panels are because some panels are more efficient than others. They could vary from around 10% to 20% so you would need twice as big surface of 10%-efficient panels than you would need with 20%-efficient panels. It means that the cheaper 10%-efficient panels could cost more in comparison with delivered power.