EIR in eQUEST is simply the inverse of the compressor only COP. It is a dimensionless number of the ratio of energy in divided by the cooling or eating energy moved.
Why does eQUEST use EIR?
eQUEST uses EIR because it is used as a direct multiple to calculate energy consumption and demand. Numbers such as COP and EER became popular due to marketing and sales people so that a bigger number means more efficient. However, they do not allow direct multiplication for compressor only energy.
The EER and COP entered into eQUEST wizard assume the condenser fan is included. However, the eQUEST engine calculates the condenser fan separately and that is why it the conversion has addition and subtraction.
Why is the HSPF calculation different?
eQUEST allows the user to enter HSPF into the wizard. However, in a more extreme sales pitch, HSPF and SEER equate to fuzzy math, in order to market the efficiency of a unit throughout multiple seasons. eQUEST uses a superior methodology to calculate what is known as part-load conditions. eQUEST calculates this through a series of unloading curves. Therefore, eQUEST converts HSPF and SEER to EIR, to allow a direct and provable calculations.