Not all local generation is from wind and solar sources, some other types of local generators are also classified as being renewable. This includes biomass generators and some hydro installations, though these are rarer. Further, while local renewables may be low, the national picture may be very different. The national grid infeed, which meets any gap between local demand and local generation, has a very different composition and may include a wind element coming from remote locations where the conditions are very different to those prevailing locally. The grid infeed is also likely to include a nuclear component which can become sizeable, and which contributes zero to the carbon intensity figures.
A further consideration is the current demand on the main supply substation (BSP). Demand changes through the day, meaning that the same level of renewable energy may constitute a different percentage level when measured against this variable demand.