The Utility Rate Calculation
page is an interface to a customizable economic analysis for DG/CHP sites.
Information about the prompts and reports are detailed below.
Utility Rate Calculation Prompt
The choices allow a user to specify the facility they would like to analyze, a base
and CHP electric rate, a time period and the costs of generator gas,
maintenance and heat recovery value.
The starting date of a
utility rate calculation is midnight on the first day of the month in the drop
down. The ending date is 11:00pm on the last day of the month listed in the
drop down. For a utility rate calculation, the period of analysis is limited
to a calendar year beginning on the starting. A selection for starting date of
"4/2003" and ending date of "5/2005" will return a utility rate analysis for
the period of 4/1/2003-3/31/2004.
There are five large
electric utility companies in New York state: Consolidated Edison (ConEd), Long
Island Power Authority (LIPA), Niagara Mohawk (NIMO), New York State Electric
& Gas (NYSEG) and Orange & Rockland Utility. Each has a wide variety
of electric tariffs, only one or a few of which a particular facility can
accept service under.
The Base utility rate
applies to the facility as if it did not have a DG/CHP System installed. The
CHP rate is the tariff that applies to the facility with the DG/CHP System.
For some utilities they may be the same rate, but for others the facility is
billed for service under a standby or cogeneration rate.
Details for the available
utility rates can be found
Generator Gas Cost
This is the cost in dollars
per million Btu (MMBtu) consumed by the DG/CHP Generator. If a default value
is entered for the facility in the database, that value will be displayed in
the prompt, otherwise it will be left blank.
Millions of Btu is used as
the reference for cost because of the many available fuel sources for
generators. Other billing units may be in cubic feet of gas consumed or
therms. A therm is 100,000 Btu, ten therms is equal to 1 MMBtu of energy.
For cubic feet, the actual
energy value must be calculated using the Higher Heating Value of the fuel.
Generator Maintenance Cost
The maintenance cost for a
generator is generally small when compared to the power produced. This field
accounts for the cost of labor and parts necessary to keep the generator
running per kilowatt-hour produced by the generator.
Heat Recovery Value
The Heat Recovery Value is
the dollar amount per million BTUs of savings realized by utilizing heat
recovery to perform a function that would otherwise cost the facility money
from a utility. This may be the cost of eliminating gas use or electric use
for previous equipment. This value may also need converting similar to
Generator Gas Cost.
Utility Rate Calculation Report
The Utility Rate Calculation
Report consists of two tables: "Monthly Electric Costs and Savings" and "Total
Monthly Electric Costs and Savings Table
This table presents a simple
analysis of the electric bills with and without the Generator for the selected
time frame. The Base Facility uses the Total Facility Demand values from the
database on an hourly time step with a data quality level of "Passes relational
checks". The CHP Facility uses the Total Facility Purchased Demand values.
These hourly values are used
to calculate monthly electric bills. For the CHP Facility, if the "Export
Electricity to Grid" checkbox is marked under the facility details, the
facility is allowed to export electricity to the grid. In the case of exported
electricity, the commodity value exported is credited to the monthly bill. If
the box is not checked, negative values for Total Facility Purchased Demand are
set to 0.
Total Economic Analysis Table
This table shows a simple
economic analysis of the full benefits of the CHP System based on the
Monitoring Unit data. The generator output and electric cost savings from the
first table are included. The generator gas use is charged based on the LHV
entered on the Facility details page and is converted to HHV using the formula:
HHV = LHV * 1.1. The maintenance cost, heat recovery savings and generator gas
costs use the values from the database and the user entered options from the
Prompts page. The values entered on the prompts page are show on footer of the
Values that are negative are displayed on the table in red and in parentheses.