Appendix B 321
Accounting for changes (other than those caused by the ECMs) is the
major challenge associated with Option C—particularly when savings
are to be monitored for long periods. See also Chapter 4.8 on Baseline
Adjustments.
ASHRAE’s Guideline 14P is expected to provide technical details
on a similar method (ASHRAE 2000).
3.4.3.1 Option C: gy DataEner
Each energy flow into a building is measured separately by the
utility or energy supplier. Where utility supply is only measured at a
central point in a campus style facility, sub-meters are needed at each
building or group of buildings on campus for which individual building
performance is to be assessed.
Several meters may be used to measure the flow of one energy
type into a building. To the extent any meter supplies energy use to a
system that interacts with other energy systems directly or indirectly, it
must be included in the whole building savings determinations. Meters
serving non-interacting energy flows for which savings are not to be
determined can be ignored, such as separately metered outdoor lighting
circuits. If several different meters are read on separate days, then each
meter having a unique billing period should be separately analyzed.
The results can be combined after each individual analysis.
Savings should be determined separately for each meter or sub-
meter serving a building so that performance changes can be assessed
for separately metered parts of the facility. Where a meter measures
a small fraction of one energy type’s total use, it may be totaled with
the larger meter(s) to reduce data management tasks. When electrical
meters are so combined, it should be recognized that small consump-
tion meters often do not have demand data associated with them so
the totalized consumption data will no longer provide meaningful load
factor information.
If energy data are missing from the post-retrofit period, a post-ret-
rofit model can be created to fill in missing data. However the reported
savings for the period should identify the report as “estimated.”
Where changes to electric demand represent a significant amount
of the calculated cost savings, the utility bill recorded demand may
not be an adequate source of data due to the difficulties of deriving
accurate models from single monthly demand readings. In this situa-
tion, the time of utility meter peaking must be known for each month