The basis of valuation for domestic dwellings is market value. For a new dwelling, the degree to which such fixed equipment would affect a band would be an estimation as to what effect, if any, such equipment would have on the market value, and hence banding, of the dwelling. No improvement will affect a valuation band on an existing dwelling unless:
(i) there is a subsequent sale, and
(ii) any such measurable increase is significant enough to move the value to a higher band.
There is, strictly, no such thing as a non-domestic dwelling in local taxation.
The same principles, however, would apply to the domestic part of a composite dwelling (a part domestic/part non domestic property), where the microgeneration equipment was provided for the domestic portion.