3.2.6 Energy Price Data

Annual energy costs shall be determined using either actual tariffs of purchased energy or the state average energy prices published by the Energy Information Administration (EIA). COMNET also provides default time-of-use rates based on state averages. Rates from different sources cannot be mixed for the same project.

Currency
Applicability	All projects
Definition	The currency used to compare the proposed design and the baseline building. Cost is the currency used for most purposes, although the Design to Earn ENERGY STAR and ASHRAE Building EQ programs use source energy.
Units	List: local energy costs, default time-of-use energy costs, EPA source energy, or site energy.
Input Restrictions	Energy modelers should use local rates when they are known and available, otherwise,
Baseline Rules	Same as the proposed design

Electric Utility Tariff
Applicability	When Currency (see above) is "local energy costs"
Definition	The local utility rate for electricity delivered to the building. The utility rate data entered under this descriptor may include a variety of rate features, such as demand charges, time of day rates, service charges, and taxes.
Units	Data structure
Input Restrictions	None
Baseline Rules	The baseline building shall use the same utility rate as the proposed design.

Gas Utility Tariff
Applicability	When Currency (see above) is "local energy costs"
Definition	The utility rates for natural gas delivered to the building. The utility rate data entered under this descriptor may include seasonal variations, service charges, and taxes.
Units	Data structure
Input Restrictions	None
Baseline Rules	The baseline building shall use the same utility rate as the proposed design.

Other Utility Tariff
Applicability	When Currency (see above) is "local energy costs"
Definition	The utility rates for chilled water, steam or other energy sources delivered to the building. The utility rate data entered under this descriptor may include seasonal variations, service charges, taxes, and other factors.
Units	Data structure
Input Restrictions	None
Baseline Rules	The baseline building shall use the same utility rate as the proposed design.

90.1-2019

3.2.6 Simulation Control

Number of Timesteps

Applicability

All projects

Definition

The timestep object specifies the “basic” timestep for the simulation. The value entered here is the number of timesteps to use within an hour. Longer timesteps have lower values for number of timesteps per hour. For example, a value of 6 entered here directs the program to use a zone timestep of 10 minutes and a value of 60 means a 1-minute timestep. The user’s choice for number of timesteps per hour must be evenly divisible into 60; the allowable choices are 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60.

If the model will include calculating the cost of electricity, then the user should be aware that many electric utility tariffs base charges on demand windows of a specified length of time. Demand windows are defined in Section 4.2 of this document. If the choice of number of timesteps per hour is not consistent with the demand window, then unexpected results may be obtained. For reasonable prediction of the maximum rates for electricity use in calculating demand charges, the length of the zone timestep needs to be consistent with the tariff’s demand window. The following table lists the values that are consistent with various demand windows.

Table 10. Acceptable Timesteps for Demand Window Values

Demand Window	Applicable Number of Timesteps per Hour
Quarter Hour	4, 12, 20 or 60
Half Hour	2, 4, 6, 10, 12, 20, 30 or 60
Full Hour, Day, Week	Any

Units

None

Input Restrictions

Maximum of 1 hour. If demand window is specified to be less than 1 hour, the length of the zone timestep needs to be consistent with Table 10 to prevent inaccurate results.

Baseline Building

Same as proposed

Not applicable for Design to Earn Building EQ.

Not applicable for Design to Earn ENERGY STAR.