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steam to heating coils in one or more air handling unit or fan coil systems. In a remote source plant, hot
water or steam is supplied to air system coils from an external source, such as a district heating system.
Modeling procedures are described below.
1. Air Systems. Define one or more air systems containing hot water or steam heating coils using the
procedures described in the previous sections.
2. Plants. Define a hot water plant or a steam plant serving these air systems. Modeling tips:
" For hot water, specify the Plant Type as "Hot Water Boiler Plant" or "Remote Hot Water".
" For steam, specify the Plant Type as "Steam Boiler Plant" or "Remote Steam".
" Boilers can be defined at the same time you create the plant using the create new boiler option
in the boiler drop-down list, or can be defined prior to entering the plant.
" Use the Systems tab in the Plant form to link the plant to the set of air systems in the building
which use hot water heating coils or steam coils. The plant will serve the combined load of all
these heating coils.
" For boiler plants, use the Configuration tab in the Plant form to define link the boiler to the plant.
" For hot water plants use the Distribution tab to define characteristics of the hot water distribution
system and its pumps.
" For steam plants use the Distribution tab to define the pipe heat loss factor.
3. Building. Link the heating plant to the building. This will include its energy use in energy cost
calculations.
6.13 MODELING UTILITY RATE STRUCTURES
This section explains how to use the program to model utility rate structures in energy simulations. The
term "utility rate" refers to the pricing structure a utility uses when billing for electric energy use or fuel
use in a building. Utility rate data is used by HAP when calculating energy costs. HAP deals with two
distinct types of utility rates:
" Electric Rates define pricing structures for electric energy use and demand.
" Fuel Rates define the pricing structures for natural gas, fuel oil, propane, remote chilled water,
remote hot water and remote steam.
While data is defined in the program in two separate data categories (one for electric and one for fuel),
both types of utility rates use the same terminology and input items and the same application concepts.
The following discussions will use electric rates for examples, but the concepts apply equal to electric
and fuel rates.
6.13.1 Basic Concepts
Individual utility companies charge for energy use, fuel use and demand in widely different ways and use
vastly different terminology in stating their pricing structures. This presents a challenge for developing
one consistent approach to modeling utility rate structures in the program. HAP uses a modular approach
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Energy Analysis Applications Chapter 6
to meet this challenge. The program provides building blocks representing the common billing
mechanisms for energy, demand, demand determination and miscellaneous charges. The user is able to
pick and choose among these building blocks to assemble a utility rate model that best represents the
pricing structure used for their building.
The key elements in successfully using the utility rate modeling features in HAP are:
1. Recognizing the separate billing mechanisms used in your utility rate structure and matching them to
the corresponding building blocks offered by HAP.
2. Understanding the common terminology used by HAP and relating this to the specific terminology
used by your utility company.
The following subsections discuss terminology and building blocks involved with the three common
components of a commercial building utility bill: energy or fuel charges, demand charges, demand
determination. Each subsection below will define terms, provide examples of the common billing
mechanisms and show examples of how data would be input in HAP. Further information on these
subjects can be found in the program's on-line help system in the sections dealing with utility rate inputs
and energy cost calculations.
6.13.2 Energy and Fuel Charges
An "energy charge" is the component of the electric bill that charges for energy consumption measured in
kWh. In a fuel bill, it is the component that charges for fuel consumption measured in units defined by
the utility. Nearly all utility rates include an energy or fuel charge; many include nothing but an energy
or fuel charge.
HAP is able to model the five most common types of energy and fuel charges. Utility rates will never
refer to the charges using the names shown below. Instead these are simply descriptive names that are
handy when explaining the pricing structures. To decide which kind of energy or fuel charge you have,
match the charge defined on your utility rate sheet with one of the following.
Flat Price. This pricing structure uses a flat cost/kWh price for all times, or specific periods such as
seasons or time-of-day periods.
Sample Utility Rate Statement:
All kWh during summer billing months............................0.077 $/kWh
All kWh during winter billing months ..............................0.049 $/kWh
Example: During one summer billing month 40000 kWh is used. The energy charge is calculated as:
kWh Range Block Size x Price = Cost
All 40000 kWh x 0.077 $/kWh = $3080
Total Energy Charge = $3080
Program Input: Use the "Standard" energy charge type. For fuel rates, all fuel charges are "standard".
Specify one step for each fixed price item. For this example, the inputs would be as follows. Note that
in HAP the energy or fuel quantity "9999999" is used to designate "all".
Season Period Block Size Block Units Price
Summer All 9999999 kWh 0.07700
Winter All 9999999 kWh 0.04900
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Chapter 6 Design Applications
Declining Block. This pricing structure uses different energy or fuel prices for different "blocks" of
energy or fuel that are consumed. Generally the price declines with each succeeding block, hence the
name "declining block".
Sample Utility Rate Statement:
For the first 8000 kWh .....................................................0.101 $/kWh
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