322 Energy Project Financing: Resources and Strategies for Success
so that the special demand recording equipment can be synchronized
with the utility’s resetting of the demand. Also the minimum time step
for any demand recording meter should match the utility’s demand time
interval (see Chapter 5.2).
3.4.3.2 Option C: gy InvoicesEner
Energy data are often derived from utility meters, either through
direct reading of the meter, or from utility invoices. Where utility bills
are the source of energy use data, it should be recognized that a utility’s
needs for accuracy in meter reading may not be the same as that of
savings determination. Utility bills can contain estimated data, espe-
cially for small accounts. Sometimes it cannot be determined from the
bill itself that data come from an estimate rather than a meter reading.
Unreported estimated meter readings create unknown errors for the
month(s) of the estimate and the subsequent month when an actual
reading is made. However the first bill with an actual reading after one
or more estimates will correct the previous errors in energy quantities.
When the fact of an estimate is shown on a utility bill, the associated
savings report should reflect this fact.
Where electrical meter estimates are made, no valid data exist for
electrical demand.
Energy may be supplied indirectly to a facility, through on-site
storage facilities for oil, propane or coal. In such situations, informa-
tion on the energy supplier shipment invoices is not representative of
the facility’s actual consumption during the period between shipments.
Ideally a meter downstream of the storage facility should be used to
measure energy use. However where there is no such meter, inventory
level adjustments for each invoice period should be used to supplement
the invoices.
3.4.3.3 Option C: independent Variables
Characteristics of a facility’s use Or the environment which gov-
ern energy consumption are called independent variables. Common
independent variables are weather and occupancy. Weather has many
dimensions, but for whole building analysis weather is most often just
outdoor temperature and possibly humidity depending upon the cli-
mate of the facility. Occupancy may be defined in many ways, such as:
hotel room occupancy factor, office building core occupancy hours or
maximum hours, number of occupied days (weekdays/weekends), or