The results of the energy and financial study indicate that Option 2, Variable Refrigerant Flow is preferred option for achieving a net zero energy building.
As demonstrated in the graph below, the two options had comparable performance for many of the energy end-uses such as domestic hot water, lighting and miscellaneous equipment. Where Option 2 (VRF) significantly outperformed Option 1 (radiant heating) was with respect to space heating.
Figure 6 - Energy End Use - Option 1 vs. Option 2
Due to the lower energy usage of Option 2 the size of the PV array required is also smaller than that of Option 1. In addition, the cost of the improvements (over baseline) for Option 2 also proves to be less expensive. However, the energy savings on a cost basis are greater with Option 2 as is the revenue from the FIT program.
As such, a straight comparison of the options only provides part of the picture. The net present value and internal rate (IRR) of return provides a clearer picture of how the two options compare. Examining the results from the NPV calculations Option 2 provides the greatest net present worth at $(74,616) with an IRR of 5%.
Through examination of the numbers the unexpected results can be explained by the cost of the improvements versus the cost of PV. Through this evaluation the strategy has been to reduce the amount of energy required by the building; thereby allowing for the size of the PV array to be downsized. On a straight cost per square metre basis, the cost of the upgrades does not appear to be unreasonable for this type of building. However, the cost of PV has become so inexpensive that the cost benefit of including the building improvements is greatly reduced. In addition to this, the cost of gas is high at a rate $0.19/m3, thus identifying a low-cost energy improvement strategy becomes challenging for a building wherein the greatest energy use is space heating. Having said this, both Option 1 and Option 2 perform better than the baseline indicating that some energy conservation measures are required to make the NPV results acceptable.
The table 10 summarizes all of the key variables for consideration.
Table 10 - Option 1 vs. Option 2 Summary