Nearly every solar customer we speak to is looking for the "best deal" and by that, they normally mean the cheapest. However, there are many factors involved in a solar photovoltaic installation which mean that the cheapest deal is very often not the best.
A solar installation needs to last for 25 years and picking the cheapest deal you can find might not turn out so well in the long run.
Take a minute to consider the following points:
Compare like to like
When you're comparing quotes ensure you compare like for like with both the make and model of the solar panels the installers are proposing. For example, there is no point comparing Sanyo 250 watt hybrid panels with Suntech 250 watt panels directly and looking at the price, since these two products are very different and will deliver a completely different number of kilowatt hours per year.
Size is not everything
Don't just look at the kWp (kilowatt peak) system size. There are a number of products with different PV technology on the market and comparing total system size alone can give a deceptive picture of any system.
For example, Yingli offer a good product classed as a 235W polycrystalline panel, which is the same wattage as the Sanyo 235W hybrid panel. Six of either of these panels would give a total system size of 1.41kWp. However, in optimum conditions in the UK climate (south facing, unshaded and on a pitch of about 35°) Sanyo hybrid panels would generate 1,310kWh per year and Yingli polycrystalline panels would generate 1,200kWh per year. The Yingli panels are a less expensive option to buy initially but also generate less kWh/kWp per year and therefore the annual income from the Feed In Tariff would be less with the Yingli panels since the Feed in Tariff scheme is based on annual kWhs generated.
Do you need extras?
Check to see if the quotes include items such as scaffolding and any other extras. Some installers offer a handheld wireless display unit as standard, in addition to the high accuracy class 1 hardwired meter required for the Feed In Tariff.
Check for other hidden costs
Ask your installer specifically if their quote includes everything required, or if there will be any other costs. A good installer will have included everything in the quoted price.
Mounting systems can vary
Ask about the quality of the components which make up the mounting system. There is lots of scope for an installer to save a few quid in the framework of a solar photovoltaic system, at the expense of the quality and durability of your system. For example, some systems are designed to last, using only the most durable of materials like hot dipped galvanised steel with stainless steel fixings for structural integrity and longevity. A PV system should be on the roof for at least 25 years although there is no reason why it shouldn’t still be there in 40-50 years. Make sure you know what your mounting system is made from and do not compromise on the quality of any of the components. There are many invisible ways to cut costs but reputable companies will want to provide you with a long lasting durable investment.
Most PV systems are individually designed to the specific roof rather than ‘one size fits all’ because roofing construction methods, topography and locations vary tremendously.
A decent installer will not sell more PV panels than fit with the structure of your roof (not just the size) and will adhere to all the quality recommendations including, but not limited to, structural weight, fixing method, wind uplift etc. A good quality company will pass all surveys through an engineering department prior to advising on the best options, to ensure the system is correct for the roof in question.
Most PV panels come with a 25 year power warranty, but these vary enormously. Check how long the panels are guaranteed for, and to what level. Solar panels also come with a materials and workmanship warranty which is equally important. Check how long this is and compare it to other brands. Your power warranty will not be worth anything if your panels fall apart when they are outside their workmanship warranty.
On top of the panel warranty most installers will offer a warranty for their workmanship. This is there to protect you if your roof starts leaking because of the solar panel installation or if the panels slip in their mountings. Check how long your installation will be guaranteed for, a good installer will offer at least 2 years and some up to 10 years, although you should also keep in mind how long they have been in business and ask what will happen if they go bust. A workmanship warranty of 10 years is not worth anything if the installer in question is no longer in business.
Whilst there are a huge range of inverters, most offer very similar performance and again the most important factor is often the warranty. A solar inverter will normally be covered for 10 to 15 years and you should expect to have to replace a fuse board at least once during the 25 years of the feed-in tariff. Try to find out from your installer how much they anticipate this will cost and make sure that the inverter manufacturer hay have selected is reputable and looks like being in business for the long term.
Most solar installers regularly benchmark their costs in the market-place to ensure they remain competitive and the best installers will be reasonably priced, but they will not be the cheapest. The companies that are offer the cheapest deals are often cutting corners at the customers expense and you would do well to avoid them if you want to get the most from your investment in the long term.