I'm working on a Core and Shell project and recently I was given the energy model made for us by a consultant. Although the scope of the project is only Core and Shell, the model covers the whole building. It's OK.

Today the Client decided that he wants to implement photovoltaic cells on the facade (= on-site renewable energy) and he asked me to calculate how much energy needs to be generated by those cells, in order to fulfill LEED requirements.

Right now I am wondering if I should:
a) take the whole building energy use and cost and multiply by 1%, or
b) take the 15% of the whole building energy use and cost, in order to have Core and Shell energy usage, and multiply this number by 1%.

For those who don't know where the 15% came from, in Green Power credit it is said that if you don't know what's the Core and Shell energy use you take 15% of the whole building energy use (correct me if I'm wrong, but I'm quite sure it's like that).

As you can imagine, it's quite a difference to take 1% or 1% from 15% of the building energy use/cost.

Please advice if this rule also applies to the on-site renewable energy credit.

Thanks!