How is Efficiency Measured?
The efficiency of solar panels is measured by the output in watts per square foot. However, if the label on a solar panel product reads 200 watts, it has to be considered that this rating was calculated by testing the module in strict laboratory conditions. The same size module may perform differently under real-life conditions.
What Can Effect Efficiency?
People from less sunny parts of the world think that solar panels won?t work very efficiently in their situation. This is a misconception relating to the term 'solar'. Solar panels do not need sunshine to make them work but they do need light. Therefore, if the panels are placed in a shaded position, they will still work but the amount of light they're exposed to will affect their efficiency. Other things that will affect efficiency are the tilt of the roof and in which direction the panels will be facing once installed.
Efficiency in Real-Life Conditions
Looking beyond the manufacturer's rating, how can anyone know how efficient the system will be in situ? The good news is that there are specialists testing currently available modules in real-life situations and publishing their results on the Internet. It's well worth doing a little research of your own before approaching any solar companies for advice. If nothing else, it will help you to know what's available; prepare you for what you can expect and what questions you will need to ask.
The Standards for Measuring Efficiency
In the US there is a system for measuring efficiency in real-life conditions called PTC, which stands for PVUSA Testing Conditions. It's also worth noting that when it comes to solar panel systems you don't always get what you pay for. These tests are showing that the most efficient systems are not always the most expensive.
Using the PTC system of measuring efficiency, The SunPower Corporation and SANYO Electric appear to be performing the best. Things are a little different in Europe where solar cells are expected to pass an MCS accreditation which stands for Microgeneration Certification Scheme and will not be accepted in the UK without this accreditation.
At the beginning of February 2011, SANYO announced that a series of their PV solar cells, called HIT, has the worlds highest conversion efficiency rate at 21.6% and has passed the MCS accreditation. This not only means that they are available in the UK but they also meet the standard of one of the government?s financial incentive schemes, Feed In Tariff (FIT).
Using Local Solar Companies to Help You Decide
Solar companies usually offer a free evaluation. A trained person will come to your home, measure up and take account of all the things previously mentioned. There may be other things, unique to your home that should be considered, like the strength of the roof in relation to the weight of the panels - and much more. This is an opportunity to discuss possibilities, compare the cost of installation as well as the price and the 'real' efficiency that you can expect.