Questions to ask your Solar PV supplier

Here are a few things you should think about asking when you’re talking to a solar PV company about getting a system fitted:

Silicon Solar PanelWhat type of panels they are going to install?

Crystalline silicon is the most commonly used Solar PV panel type in the UK and is the most efficient at converting sunlight into electricity. Crystalline silicon panels consist of thin slices of silicon cut from a single crystal (monocrystalline) or from a block of crystals (polycrystalline). This manufacturing is expensive to do, so crystalline silicon panels cost more. Monocrystalline panels are the top of the range and perform more efficiently than polycrystalline panels, with modules typically converting 15% of solar radiation into electrical energy, and best examples reaching 21.5%. They’re usually more expensive as a result. Polycrystalline silicon panels typically convert between 8 and 12 per cent of solar radiation into electricity.

The other type is of solar panel technology uses ‘Thin film’ technology, which involves depositing very thin layers of photosensitive material onto a low-cost backing, such as glass, stainless steel or plastic. This technology is cheaper and more suitable for mass production. However, the efficiency rates are correspondingly lower. There is a range of ‘Thin film’ types available:Thin Film Solar Panel

  • Amorphous silicon (4-6% efficient)
  • Cadmium telluride (7% efficient)
  • Copper indium diselenide (9%)

Ask your installers for the panel manufacturers’ Cell and Module efficiency – this will tell you what percentage of sunlight the panels convert to electricity.

What warranties do they provide you?

This is very important as the panels will be on your roof for the next 20 years at least. Ideally you should ensure that the panels are at least guaranteed for the life of the Feed-In Tariff (20 years), and that there is some sort of performance warranty, which will typically be percentage performance degradation after a number of years. This will give you a very clear indication of quality and where any cost disparity is coming from.

The same will apply to the inverter – it is likely that you will have to replace the inverter during the life of the FIT, so it is worth seeing if you can get one with a longer warranty.

What are the system’s ongoing costs?

Your solar PV system will come with ongoing costs. The inverter will most likely need to be replaced at least once in the life of your system; it is essential and the system cannot operate without it. Inverters cost around £500 to replace. There is also some repair and maintenance that you will need to do to keep the panels clean and serviceable and if you cannot do this yourself you will have to ask someone to assist you.
Microgeneration Certification Scheme
Other things you should watch out for
Here is a short list of only some of the things you should watch out for, but you should get at least 3 quotes to ensure that you fully understand all the variations:

    • Ensure that you are only being charged 5% VAT
    • Check the payback calculations carefully and try to understand them. They should be tailored to your home and not a “typical home”.
    • Ensure that they send a surveyor who does the basics; checking the roof to make sure that degree of overshading, roof tilt, angle and structure are suitable, and checking the loft and where the invertor and cabling will go. A lighting repair services company can help you with all the interior electrical changes.
    • Always ensure that the company is MCS accredited.

The Feed-in-Tariff is still available; see what you can earn by completing our free energy assessment now!

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