Annual Solar Radiation Table

Angle	Orientation of Array
	South	SE/SW	E/W	NE/NW	North
Horizontal	933	933	933	933	933
30°	1042	997	886	762	709
45°	1023	968	829	666	621
60°	960	900	753	580	485
Vertical	724	684	565	427	360

Shading Categories

Shading Category	% of Shading	Overshading
Heavy	> 80%	0.5
Significant	60% - 80%	0.65
Modest	20% - 60%	0.8
None or very little	« 20%	1.0

Solar PV

Is your home suitable for a solar panel installation? Fill out the form below and we’ll get one of our surveyors to visit and assess your property for a solar PV system. The survey takes around 1 hour and by the end of it we’ll be able to give you an accurate idea of the both the cost and payback for your specific situation.

Step 01: Your postcode

Step 02: Drag the marker onto your roof

Step 03: Submit these details to us

Click here to continue!

Output Calculator
Benefit Calculator

The Solar PV industry is regulated by the Microgeneration Certification Scheme (MCS) and all registered installers are required to use the Governments approved SAP mechanism to calculate your systems output. Unfortunately there is a 2005 set of figures and a 2009 set of figures and there is some uncertainty as to which set should be used by MCS installers. We have opted to play it safe and use the 2005 set which show a lower output than the later 2009 figures. We do this because we would prefer that your system out-performs your expectations rather than promise a larger output which you may not achieve.

The basic formula is as follows:

0.8 x kwp x S x ZPV

0.8	This basically reduces the performance of your system down from 100% to 80% to allow for loss of efficiency. Because we carefully design your system for optimum performance and use only high quality components we can gain quite a bit of this 20% back.
Kwp	This refers to the total size of your system. Typically we will use: 20 x 190W panels, so 20 x 190w = 3800wp (or 3.8Kw).
S	This refers to the annual solar radiation taken as an average across the UK over the past 10+ years. These figures have been compiled by the Government and it is these figures that are often ‘Manipulated’ by the more unscrupulous salesmen in our industry. To view the Government figures for Annual Solar Radiation CLICK HERE
ZPV	This refers to the amount of shading that is likely to fall on the array. Shading is the item that potentially has the most negative impact on the performance of your system. The panels are wired in series (or strings) which means that if there is any shading on an individual panel it will bring down the performance of all the panels in that string. Our designers are careful to ensure that we minimise the effect of shading on your system so we take note of all potential shading issues that we find during our survey such as chimneys, trees, aerials, soil pipes etc, and try to design the strings around them. When calculating your output the SAP figures offer 4 shading categories. To view the shading categories CLICK HERE

Once we have completed our survey and designed your system we can accurately quote for the complete installed cost. The financial income (benefit) of your system is comprised of 3 factors:

1. The Feed in Tariff (Fit) Payment

You get paid for every watt of energy you generate. We fit a generating meter between the inverter and your consumer unit (fusebox) which logs every watt produced by your PV array and it is this figure that is used by the utility companies to calculate your payment. These payments are index linked and tax free for a period of 25-years.

2. Energy Offset

Because you are now generating your own electricity you will obviously not be using as much from your supplier. Obviously your system will only be producing electricity during daylight hours so this is where you will find the greatest savings. That being said the power produced by your system is uneven and will fluctuate in sync with the light levels in real time. For example if the sun is blazing and you turn on the oven the output from the array may be sufficient to meet this requirement, however if a cloud passes the output will fall and if it is not sufficient to meet the demand of the oven then you will automatically pull power from the grid – i.e your power company. The energy offset figure you can expect to see is Bottom line, be a bit careful about what you plug in during the day or you could see your bills actually increase!!

3. Export Tariff

This is the electricity you produced that you don’t use yourself and which is exported back to the grid. Because of the high cost of fitting meters to track this on domestic systems, the power companies are happy to assume that 50% will be used by you and 50% will be exported back to them for which they will pay you a rate of 3p per watt.