There are four main factors that will impact how much energy a solar PV system will generate.
- Shading
- Orientation
- Angle
- Array Size
Shading
First thing in the morning and last thing in the evening it is possible that surrounding buildings or trees may partially shade a PV array, when the sun is low in the sky. Providing this is however for only about an hour after sunrise or before sunset, this will only have a very small impact on the annual energy generation, as very little power will be generated then anyway.
It is important however to ensure that your PV array will not be shaded during the main part of the day and so avoid placing your array where there will be significant shading from surrounding buildings or trees.
Detailed below is the official definition of shading that Myriad Solar uses in its calculations.
| Overshading | % of sky blocked by obstacles. | Overshading factor |
| Heavy | > 80% | 0.50 |
| Significant | 60% - 80% | 0.65 |
| Modest | 20% - 60% | 0.80 |
| None | < 20% | 1.00 |
Orientation
The sun rises in the East and sets in the West, but never goes North. Clearly therefore the more that a solar PV array is facing South the more direct sunlight it will receive and the more energy it will produce.
In general you should only site a solar PV array so that it faces between the South East and the South West otherwise its energy generation will be significantly reduced.
Angle
The sun spends most of time relatively high in the sky and therefore to ensure that a PV panel maximises its exposure to direct sunlight it should be mounted at an angle.
In the UK latitudes, the best angle is between 30 degrees and 45 degrees from horizontal.
Array Size
Clearly the larger the array of solar PV panels the more energy it will generate.
A typical single PV panel is 1,600mm X 800mm and may be mounted either horizontally or vertically as required. Any number of panels may be combined into a single array as required.