Filtering out the non-PNW sites, which the subcommittee generally agreed is a good idea, gives us the following points. We fit a trendline (through the origin) to the fan-only savings (blue points) whose slope suggests approximately 116 kWh/ton/1000hrs. This is the basis for our revised proposed savings estimate for the ARC-lite measure (fan-only savings).
On the same graph, notice the full ARC savings (red points) for PNW sites do not seem to support a strong relationship between savings and hours of operation. We hypothesize that the additional savings achieved from the full-ARC measure, which we call “compressor savings” here (green points) are much less sensitive to RTU annual operating hours. As a reminder, these are the savings represented by the additional economizer control and DCV requirements of the full-ARC measure. So our proposal is to estimate the compressor savings as a kWh/ton metric, independent of operating hours, and add that to the fan-only savings (kWh/ton/1000hrs) to estimate savings for the full-ARC measure.