The computer performance approach allows for the modeling of the PV system performance by taking into account PV system size, climate, panel orientations, inverter efficiency, and shading characteristics. The standard design PV system size is determined by the modeled annual electrical consumption of the mixed-fuel proposed design building, regardless of the actual fuel type of the proposed design building. The performance method allows for modeling different PV sizes, solar thermal systems, more energy efficiency measures, battery storage system and other demand response measures.
The six allowable exceptions to the prescriptive PV requirements listed in 7.2.2. can also be used under the performance approach. User must select the appropriate exception in the software and provide documentation to the building department with the building permit application.
The installed PV system must meet the applicable requirements as specified in JA11.
Example 7-5 Efficiency Tradeoff
Question:
Does the performance path allow tradeoffs between PV systems and energy efficiency measures? How about tradeoffs between a PV system that is couple with a battery storage system and energy efficiency measures? How about a standalone battery storage system?
Answer:
Beginning with the 2019 Standards, the performance path no longer allows installing a larger PV system in exchange for less energy efficiency measures; however, the software will allow installing more energy efficiency, demand responsive measures, battery and storage and thermal storage systems in exchange for a smaller PV system.
When the PV systems is coupled with at least a 5 kWh battery storage system, the performance path will allow a portion of the available credit to be used for efficiency measure tradeoffs; this is a modest credit that can be used to achieve compliance in buildings that have marginal difficulty achieving compliance.
The Standards do not recognize standalone battery storage systems that are not coupled with a PV system and no compliance credits are granted for these systems.
Example 7-6 Solar Thermal System
Question:
Does a solar thermal water heating system still qualify for compliance credit in the performance path?
Answer:
Yes, although a solar water heating system cannot serve as a substitution for the prescriptively required PV system, it can still be installed along with PV for optional compliance credit in the performance path. Solar water heating systems are modeled along with the remainder of the water heating and distribution systems as part of the efficiency EDR score, and can be used for efficiency measures tradeoff, or installing a smaller PV system. The requirements for solar thermal water heating systems are described in Chapter 5.
Example 7-7 Precooling
Question:
Can you explain precooling strategy requirements and how to comply with them?
Answer:
Precooling is a strategy that allows cooling the house by two or three degrees below the setpoint in the hours preceding the onset of peak time-of-use (TOU) hours, when the electricity rates are relatively low, and then turning off the air conditioning during the TOU peak hours, resulting in significant cost savings for the building occupants.
To obtain this credit, a JA5 compliant communicating thermostat must be installed in the dwelling unit, and indicated on both CF1R and CF2R forms.
The precooling credit may only be used to lower the EDR score towards a more stringent EDR goal set by a reach code such as a local ordinance; this credit cannot be used to tradeoff the energy efficiency features of the building.
Finally, if the dwelling unit is already equipped with a battery storage system coupled with a PV system, the precooling strategy may have negligible impact on further lowering the EDR score.