How many years does it take to sign a contract for photovoltaic panels

Based on the Energy Saving Trust's figures, it could take someone living in the middle of the country, in a typical home, anywhere between 11 and 14 years to recoup the costs of installing panels, . [pdf]
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How much tilt should photovoltaic panels have to be to be effective

To optimize performance, tilt your panels at an angle that is 10-15 degrees less than your latitude. For example, if you live at a latitude of 40 degrees, set your panels at about 25-30 degrees. [pdf]