Verifying the energy savings
Options overview – Option A – Option B – Option C – Option D
Option A is intended for retrofits where operating hours are known in advance, stipulated or agreed upon, and where end use capacity, demand or power level (kW) can be assessed by either:
One-Time, In-Situ End-Use Measurement Method. One-time, in-situ end-use measurements are measurements taken at the site using calibrated instrumentation. For electrical loads, this type of measurement usually requires isolating the device to be measured and measuring the electrical power (RMS Wattage) that the device draws on all phases.
Representative Sample Measurement Method. Representative sample measurements are measurements taken with calibrated instrumentation on a representative sample of equipment being installed. Representative sample measurements are appropriate for energy consuming equipment that does not vary significantly in load and must be taken on similar equipment model types. Estimates using representative sample measurements and stipulated consumption may be adversely affected by inaccurate one-time, in-situ measurements if proper care is not exercised.
Representative Manufacturer’s Measurement Method. Representative manufacturer’s measurements are measurements published by the manufacturer of the equipment. In order for such measurements to be valid, they should be taken with calibrated instruments on a representative sample of equipment being installed. Estimates using manufacturer’s sample measurements and stipulated consumption may be adversely affected by the same factors as one-time, in-situ measurements.
Representative Baseline Power Level Profile Method. Representative baseline power level profiles are either hourly or 15-minute measurements taken at the site usually at the whole-facility level or sub-panel level using portable monitoring equipment. These measurements represent an aggregate end-use load, e.g., all lighting loads in a facility. Representative baseline power level profiles capture the in-situ 24-hour profiles of a group of equipment operating during weekday or weekend modes. Such measurements are appropriate for non-weather-dependent energy consuming equipment loads that vary within a 24-hour period, but do not vary daily by more than plus or minus ten percent (±10%). Example: weekday/weekend whole-facility lighting. In general, representative baseline power level profiles can be used to measure weather-independent loads. Representative baseline power level profiles for weather-dependent loads should include measurements taken over a long enough period to adequately characterize the schedule (i.e., weekday/weekend and weather-dependent characteristics of the end use load).
Energy savings are stipulating by multiplying the difference between baseline and post-installation measurements by the stipulated hours-of-use or hourly profiles.
However, these can be adversely affected by the following factors. Savings stipulations:
may vary if there are equipment changes during the retrofit that affect equipment operating efficiency.
may vary if operating settings that affect facility system performance are changed after measurements are taken.
may vary if there is a significant number of lamp outages, or if the actual operating schedule varies significantly from the stipulated operating schedule.
do not measure cooling interaction or increases in heating load due to reductions in internal heating caused by improved lighting system efficiency.
may vary when manufacturer’s wattage is used if in-situ lamp-ballast-fixture temperature is significantly different than standard conditions that manufacturer’s use for published fixture wattage.