There are two independent EDR metrics based on source energy and TDV. The EDR metric based on source energy is referred to as EDR1 and the EDR metric based on TDV is referred to as EDR2. No tradeoffs are allowed between EDR1 and EDR2.
EDR1 is a dimensionless metric based on the hourly source energy consumption of a proposed or standard design divided by the hourly source energy consumption of the reference design. EDR1 accounts for the source energy of all end-uses, including space heating, space cooling, ventilation, and water heating, interior lighting, appliances, exterior lighting, PV generation and flexibility measures, as well as The Renewable Portfolio Standards (RPS) and similar obligations.
In addition to efficiency, projects receive EDR1 benefits from generating renewable energy and shifting energy demand to times when the utility generates low-carbon electricity. The EDR1 is a way to express the energy performance of a building using a scoring system where 100 represents the energy performance of a reference design building meeting the efficiency requirements of the 2006 International Energy Conservation Code (IECC). A lower EDR1 score represents less source energy use. The proposed building must have an EDR1 score that is equal to or less than the EDR1 score of the standard design.
The physical bounds for source energy are about 10,500 British thermal units per kilowatt-hour (Btu/kWh) upper bound (proxy low-efficiency power plant) and 0 Btu/kWh lower bound (renewable generation). Delivery losses are the same as the delivery losses used for TDV.
Avoided source energy from incremental renewable generation varies based on (RPS) goals. This source energy is a represented as an RPS percentage value that increases annually. The avoided source energy can further vary based on the specific resource used, such as wind, solar or energy storage.
Natural gas long-run source energy is based on the percentage of renewable gas used by utilities. Increased use of renewable gas will decrease the source energy impact of retail natural gas consumption.
Propane long-run source energy does not vary annually because there are no renewable gas offsets that can be used to support propane. The long-run marginal source energy of propane is constant and considered to be the source energy of propane gas. This long-run marginal source energy is calculated as a direct conversion factor of 100 kBtu/therm.
The hourly source energy determined by the CEC is used to determine compliance.
EDR2 is a dimensionless metric based on the TDV energy consumption of a proposed or standard design divided by the TDV energy consumption of the reference design.
The EDR2 is a way to express the energy performance of a building using a scoring system where 100 represents the energy performance of a reference design building meeting the efficiency requirements of the 2006 IECC. The EDR2 is similar to the energy rating index in the 2014 Residential Energy Services Network (RESNET) standard. A score of zero represents a building that has zero-net-energy consumption based on the TDV energy consumption. By combining high levels of energy efficiency with renewable energy generating or demand flexibility measures, a score of zero or less could be achieved.
Buildings complying with the current California Building Energy Efficiency Standards are more efficient than the 2006 IECC, so most newly constructed buildings will have EDR2 scores below 100. Buildings with renewable generation can achieve a negative score. If an EDR2 is calculated for an older, inefficient home, the score would be more than 100.
The Total EDR2 is composed of two components, Efficiency EDR2 and PV/flexibility EDR2.
The efficiency EDR2 is based on the energy efficiency features of the building. PV/flexibility EDR2 includes the effects of the PV system, battery storage system, precooling, and other demand-responsive measures. Total EDR2 combines the efficiency EDR2 and PV/flexibility EDR2 into one final score.
The efficiency EDR2 does not include solar electric generation but can include a self-utilization credit for batteries. The total EDR2 includes the effects of solar generation and any battery storage beyond the self-utilization credit.