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Questions to Ask Solar Panel Installers
Ask the right questions when getting quotes for Solar PV
There's a considerable initial cost to an Solar PV system so you really need to make sure you do your research. Here's a list of questions that you should ask an company that provides you with a quote for Solar PV.
Will you be able to provide a quote and answer questions during the site visit?
When you make an appointment for an installer to do a site visit check that they are going to be able to provide a quote on the day or immediately afterwards, and that they will be able to answer your questions.
Most vendors were able to provide a quote while they were still at our house and answer all of our questions about the technology and the government feed-in-tariffs, etc.
We were caught out by one exception. The guy turned up as expected, did a site survey and then told us he wasn't trained to do anything else and that we'd get a quote in two weeks (it actually took longer than that). If you're close to the decision point then a visit like this is a waste of time.
Is Solar PV suitable for my property?
Pretty much the first thing you expect a vendor to do is to check the orientation of your house. You need a roughly south-facing house - south east to south west is the general rule.
They should also confirm that your roof can take the weight of the panels and is in good enough condition, and that you don't have excessive shading (trees, other buildings etc).
Solar PV is not suitable for all homes. The installer should quickly check these factors.
Are you MCS Certified?
This one is really important. In order to receive government feed-in-tariff payments your photovoltaic solar solution must be fitted by MCS certified installers. Check your installer is on the list of MCS Certified Solar Photovoltaic Installers.
What is the size of the system?
The size of a solar PV installation is measured in kilowatt peak (kWp) and will be roughly in the range of 1kWp (small system) to 4kWp (large system).
Note that the government feed-in-tariff maximum payment only applies to systems up to 4kWp.
The installer should tell you how many panels will be installed. Panels from different manufacturers are different sizes and outputs, but you can expect the number of panels to be in the range of 4-16. The installer should know the dimensions of the panels and be able to explain how they will fit on your roof.
How much will it cost?
An obvious one! A guideline is Â£4000 per kWp.
You should check whether VAT at 5% is included in the quote.
And how long the quote is valid for. Personally I'm uncomfortable with any offer that is reduced if you sign on the day. I'd far rather have a realistic quote in the first place and time to consider.
How much electricity will the system generate?
This figure should be roughly 800 * the kWp for your system e.g. 4 x 800 = 3200 kWh per year.
But this figure is dependent on your location (the further south the better) and the system efficiency.
The installer should be able to explain how they come to the figure.
What payments and savings can I expect?
In the first year the calculation is:
Electricity Generated in kWh x FiT generation payment + Electricity Used x Electricity Unit Cost + Electricity Exported to the Grid x FiT Export Tariff
E.g. 3200 x 0.413 + 1600 x 0.10 + 1600 x 0.03 = Â£1529.60
But you really need to factor in the cost of the original system, affect of inflation, etc to understand what this really means.
The calculation is explained in detail in the Payback from Photovoltaic (PV) Solar Panels in the UK lens.
And we've developed a solar pv payback calculator to help you estimate this (coming soon).
When are payments to the installer due?
You shouldn't have to pay the full amount upfront. It's normal to pay an initial deposit and the remainder on completion.
What is the guarantee?
Check what guarantees and warranties are included.
It's pretty typical to see a several year warranty on the inverter - this is the component most likely to fail during the life of the system. It's likely that the inverter will fail outside of this guarantee period and will need to be replaced. Extended warranties may be available.
You should also get a product guarantee on the solar panels for several years. Solar panels are pretty simple so if they survive the first few years without any manufacturing faults becoming apparent then there's a good chance of them lasting longer than the 25 years covered by the feed in tariff.
You should also look for an output guarantee. This will typically guarantee a particular output level for a period of time. This protects you against the output of the panels reducing significantly over the life of the system.
Here's an example >a href="http://www.sharp.co.uk/cps/rde/xbcr/documents/documents/Marketing/Brochure/SHARP_Solar_Guarantee_Crystalline_Modules_3_01_en_de_fr_esp.pdf"> Solar Panel Guarantee from Sharp.
The there's the workmanship itself. The installers need to be MCS certified, this is supposed to guarantee a certain level of competence and service, but it's unclear precisely what this means.
When can you install?
Check what their lead time is from when you agree to go ahead. It might be a great quote, but if they can't install for six months they may not be your first choice.
What solar panels and inverter will you use?
The installer should be able to tell you the manufacturer and model of the panels and inverter they are proposing to install. The you can check out the specifications and the prices of these components so you understand what you are getting for your money.
Your installer should tell you whether the proposed panels are monocrystalline or polycrystalline (two slightly different technologies). There doesn't seem to be much to choose between them on a technology basis.
It's often said that monocrystalline is more expensive per Watt. But it didn't work out that way for us. And the smaller size of the mono panels (they require slightly less surface area for the same output and are more efficient) meant we could fit a greater capacity system on the roof.
The overall output/price ratio is the important factor, keeping in mind that a larger system will deliver larger FiT payments and therefore greater payback.
What does installation involve?
The installer should be able to explain how the panels will be attached to the roof.
They will need scaffolding so they should check access.
And internally they will need to install an inverter (typically in the loft) and run cables to the main distribution unit. Check whether cables will be routed inside or outside the house and what the end result will be
Installation of solar panels is pretty quick, around 2 days.
Who is responsible for informing the electricity supplier?
Your electricity supplier will need to be informed about the installation of a solar PV system so that you can export unused electricity to the grid and receive Feed in Tariff payments.
You should also ask your electricity provider how the process works and when and how payments will be made to you. As an example here are the E.On Feed In Tariff Terms and Conditions.
Can you provide references?
A good installer should be able to provide references from happy customers. Perhaps you can even ask them if actual output matches predicted output.
Solar Panels require a significant outlay. It's important to that you learn as much as you can on the subject. Michael Boxwell's book has been recently updated to include information on government incentives and gets good reviews: Solar Electricity Handbook 2010: A Simple Practical Guide to Solar Energy - Designing and Installing Photovoltaic Solar Electric Systems
Have we missed any important questions? Or got anything wrong. Any other feedback. We'd love to hear from you.