Economic payback is defined as the number of years it takes to recoup the money that the system cost to install (and maintain) originally.

WIND SYSTEMS: The initial system installation cost is very similar from site to site, however the income earned (directly related to electricity generated) varies considerably. For example a very windy site with a mean wind speed of 7 m/s will 'earn' twice that of an average wind site with a mean wind speed of 5 m/s. This obviously means means that economic payback time will be half!

Typical payback time can vary from 3-10 years (with existing Feed In tariff's)

PV SOLAR SYSTEMS: Again, the initial installation cost does not vary much from site to site (unless the roof is difficult or very high). However, unlike the wind sites, this is also true for the income earned - unlike the wind, the suns irradience is quite similar over the year, within the same region (e.g. south UK, Midlands, North, Scotland etc).

Typical payback time tends to be 10-12 years (with existing Feed In tariff's.)

Of-course the income generated (tax-free) by any renewable generator includes such things as: