Karen,

I gave a presentation on this subject with a member from USGBC and this
exact question was brought up. The answer was to use the local rate for
both systems. LEED/ASHRAE require that the energy rate be the same for
both the baseline and proposed designs. Fuel and electricity rates are
assigned using the local utility rate schedules as they would normally
apply to the building and using the normal ASHRAE and LEED modeling
rules. This line while a little ambiguous means that you should use the
rate that would be applied to the building if it was not connected to
the plant, not the discounted rate that the plant most likely receives.

Thanks

Seth Spangler, LEED(r) AP