Potential sites must have a suitable roof and the capacity to use most of the electricity generated on site. The owners must be willing to sign a twenty-year roof lease.
Roof
The roof must be reasonably large. To be commercially viable, the smallest systems we can install will be 30 kWp. These require 80 panels 2m2 panels (i.e. an area of at least 160m2).
It must not be shaded by trees, parapets or other roofs or other buildings. Partially shading will may be acceptable but will reduce the amount of electricity that can be generated.
The roof must be flat or orientated towards the sun (the more southerly the better).
It must be sufficiently well built to for the panels to be installed and secure over their twenty-year lifetime.
Electricity use
Because we don’t get very much money for selling electricity back to the grid the user needs to be able to use most of the electricity generated. It might sound obvious, but this means that users of the building will need to be using electricity when the sun is shining. That is during the day, throughout the week and over the summer.
A 30 kWp system will probably generate about 26,000 kWh per year. Annual on-site electricity use will probably have to be at least double this to be able to use enough of the electricity generated to be economically viable.
Owners
Owners need to be willing to agree to the following for the twenty-year period required for the scheme to be economically viable:
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a roof lease allowing installation and maintenance of the panels,
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a purchase agreement to buy the electricity generated.
The panels remain the property of the community benefit society who take responsibility for their maintenance and insurance.
If owners have access to the capital required, then they will generally get a better long-term financial return by installing panels themselves than though a scheme like this. The payback period for solar panels is typically between 6 and 10 years after which owners continue to benefit from almost free electricity generation (there are some ongoing maintenance and insurance costs).
