Solar Panel efficiency explained
What do we mean by efficiency?
When discussions about solar panels occur, the subject of efficiency usually comes up.
But what is meant by Solar Panel Efficiency?
Solar cell and solar panel efficiency are different
Solar panels are made up of individual solar cells; typically 60 cells/panel arranged in 6 columns of 10. It is the solar cells that produce the electricity; the rest of the solar panel simply provides support for the cells or gathers the electricity to pass it on to the next solar panel in the solar PV system.
Solar cell efficiency is the rate at which a solar cell converts sunlight into electricity. Cell efficiency is measured in Watts/M2. Cell efficiency will always be higher than panel efficiency because 1M2 of solar panel also has a frame and there are gaps between the cells, neither of which produce electricity.
Types of solar cell
The most common solar cells are: monocrystalline silicon (mono), where each cell is made from a single silicon crystal or polycrystalline silicon (poly) which consists of multiple silicon crystals.
When we started installing Solar PV systems 4 years ago there was a clear difference in efficiency between mono and poly cells, with mono being approx 15% efficient and poly approx 13% efficient.
Today, both types of cell have roughly the same efficiency at approximately 15%. Advances in manufacturing now produce cell efficiency of up to 18% but the majority of panels are 15% – 16% efficient.
There are other types of solar panel available such as thin film, hybrid or copper backed panels, which are up to 20% efficient. These are often used in specific applications such as when there’s a shortage of space. However we’ll focus on mono & poly solar panels: if you’d like to discuss this please call us.
How important is efficiency?
In some ways it doesn’t matter.
If one panel is less efficient than another you just need a larger area to produce the same amount of electricity. 250kW is still 250kW regardless of the space used to produce it.
If space is not at a premium, then there is no need to choose high efficiency panels, instead you should look at factors such as cost and product reliability when choosing your panel. However if space is a premium, then it is worth considering higher efficiency panels, although these may cost more, they will be your best choice.
So, what does this all mean when choosing a solar panel?
For large roofs, using a more efficient panel you will get a higher capacity system installed and generate more electricity. This in turn means more income from the system. However, it will be more expensive to install, giving a lower return on investment (ROI) than a lower cost and lower efficiency solar PV system.
Costs involved in solar PV system installations
Solar panels and inverters make up approx 60% – 70% of a Solar PV system’s cost. However there are other costs in a solar PV installation:
- Scaffolding to work safely on the roof
- Labour is the same cost per panel irrespective of panel efficiency
On smaller roofs these fixed costs represent a disproportionately high percentage of the overall cost of the system. So In this case more efficient panels will have a higher installed capacity, generate more electricity and income, but also have better rates of return on investment compared to lower output panels. For larger roof areas, a lower efficiency panel system might make more sense.
To ensure the optimal choice and location of panel and inverter, we always visit the property to carry out a site survey so we can advise customers on the ideal system for their building and budget.
Other factors you will want to consider
Solar panels are available in different colours, blue or black cells; also there are black EVA backing-sheet and frame or standard white EVA and anodised aluminium frame versions.
The choice is not all about looks either, as panel temperature has a significant impact of on the cell / module performance. A five degree centigrade rise in temperature reduces cell efficiency by 1%.
A full black panel will heat up more on a sunny day than a standard panel with an aluminium frame. The extra heat produced will reduce the black panels output. This is why commercial applications such as solar farms will use standard aluminium framed panels with white EVA backing as they heat up less and maintain higher efficiency.
Black panels are often considered aesthetically appealing but they cost more and may give a lower output overall than an equivalent (and cheaper) aluminium framed panel. Aluminium framed PV panels therefore, offer the better choice for best ROI.
For an informed and impartial discussion about solar PV panels, call us now on 01480 819 740.
You can also request a call back using our handy form.