Each system is different and most companies offer a payback within 10 years but because of our prices we can offer payback sometimes within 4 years offering 14 years of pure tax free profit for a well sited PV system on a property with high energy consumption.
Both of these types of panels do exist. At UK Solar Generation however we only fit solar panels that lay on top of your roof as they are more cost effective. The solar tiles are generally only used if your roof needs replacing or for new build projects.
Single people in small energy efficient houses might only use a 1kW at a time but a larger system is often more beneficial due to the economies involved on the installation process as every kWp is paid for at the feed-in tariff rate regardless of the use.
Solar panels are designed so that any dirt or dust will wash off when it rains so it is unlikely that your panel efficiency will be affected by dirt. In extreme cases it has been shown that panels can lose up to 10% of their efficiency due to dust.
The solar panels we provide have a warranty of 25-years, but have been show to last much longer with some still working over 40-years. It is estimated that performance will decrease by under 1% per year, which would mean that in 50 years they’d still be 60% efficient, but nobody really knows past the guarantees given.