How results are calculated
What InverseHub compares on each compliance path, in plain words. The calculation on your project page shows the same steps with your numbers.
On this page
Energy cost first
Every path starts from the annual energy cost of each design, from the utility rates in the reports. On-site renewable energy and exceptional calculations you entered in SimReader are subtracted from the proposed design. New off-site renewable energy is subtracted only from the proposed design’s GHG emissions, for LEED v4 with the 2024 energy update.
Performance cost index (ASHRAE 90.1-2016 and later)
The proposed design complies when its performance cost index is at or below the target:
- PCI = proposed building performance ÷ baseline building performance, where both are annual energy costs.
- PCIt = (baseline unregulated energy cost + BPF × baseline regulated energy cost − PRE) ÷ baseline building performance.
Where:
- BPF is the code’s building performance factor for the building type and climate zone. With several building area types, InverseHub uses the area-weighted average.
- PRE is the energy cost of the on-site renewable energy the code requires (90.1-2022 and the codes based on it). It’s zero otherwise.
- On-site renewables count toward the PCI up to 5% of the baseline building performance; with a PRE, only renewables beyond the required system count.
Energy index. With the energy method, the same formulas use site energy instead of cost. Codes with their own energy rules use their own BPF tables and conversion factors: source energy for NYC 2020, site energy for NYC 2025 and New York State 2025. ASHRAE 90.1-2022 and Oregon 2025 offer site energy, source energy or carbon. If you enter local conversion factors for electricity and gas, InverseHub recalculates the BPF from them with the code’s coefficients.
Earlier ASHRAE 90.1 editions (2007 to 2013)
The Performance Rating Method compares the proposed design’s energy cost with the baseline building’s. It passes when the proposed cost is lower. With the energy method, it compares site energy.
Energy Cost Budget Method
The design energy cost (DEC) of the proposed design must be at or below the energy cost budget (ECB), the budget building’s annual energy cost.
- From 90.1-2016 on, on-site renewables are credited up to 5% of the budget.
- In 90.1-2022, the budget is reduced by the required energy credits: ECB × (1 − credits ÷ 1000 × the additions and alterations factor). The required on-site solar’s cost (PRE) comes off the budget, and only renewables beyond it are credited.
Total Building Performance (IECC)
The proposed design’s annual energy cost must be at most a share of the standard reference design’s:
- 100% for IECC 2006 and 2009; 85% for IECC 2012 to 2021; 80% for Chicago 2022; 85% for New York State 2020.
- For IECC 2018 and 2021, and Chicago 2022, on-site renewables count up to 5% of the standard reference design’s energy cost. For the other editions, they’re subtracted from the proposed cost.
IgCC
- IgCC 2012 and 2015: the zero energy performance index (zEPI) compares source energy use intensities: zEPI = 57 (2012) or 52 (2015) × proposed EUI ÷ standard reference EUI. It must be at most 51 (2012) or 50 (2015). The proposed design’s CO₂e emissions are checked too. On-site renewable energy is subtracted from the proposed design’s energy and emissions.
- IgCC 2021: the cost PCI and the source-energy zEPI against their targets, which the building’s renewable fraction lowers. Also checked: CO₂e emissions, and the PCI without renewables against the ASHRAE 90.1-2019 target.
- Source energy and CO₂e factors come from the code. Electricity uses the factors of your project’s EPA eGRID subregion.
LEED v4 with the 2024 energy update
The Optimize Energy Performance points add up two metrics, each with its own thresholds for your rating system.
Energy cost or source energy
InverseHub works out both savings and uses the higher one:
- Energy cost savings = 1 − proposed annual energy cost ÷ baseline annual energy cost, after on-site renewable energy and exceptional calculations (see Energy cost first).
- Source energy savings = 1 − proposed source energy ÷ baseline source energy. Each design’s source energy is each fuel’s annual site energy times its source-to-site ratio, added up. On-site renewable energy counts as zero source energy: it reduces the proposed design’s purchased electricity, up to all of it. Exceptional calculation savings are subtracted at their fuel’s ratio.
The LEED Minimum Energy Performance Calculator accepts two sets of source-to-site ratios. InverseHub works out source energy savings with both and keeps the set that gives the higher savings, so it never gives fewer points. A line under the points in the conclusion names the set used and the other set’s result.
| Energy type | ASHRAE 90.1-2022 | ENERGY STAR Portfolio Manager | Canada |
|---|---|---|---|
| Electricity | 2.64 | 2.80 | 1.83 |
| Natural gas | 1.09 | 1.05 | 1.06 |
| Propane | 1.15 | 1.01 | 1.00 |
| Fuel oil and diesel | 1.19 | 1.01 | 1.00 |
| District heating | 1.20 | 1.20 | 1.33 |
| District cooling | 0.91 | 0.91 | 0.57 |
| Other fuels | 1.00 | 1.00 | 1.00 |
- ASHRAE 90.1-2022 gives no ratios for district energy, so both US sets use Portfolio Manager’s.
- Canadian projects use Portfolio Manager’s ratios for Canada, the only set there.
- Projects in other countries are worked out with both US sets, as above.
GHG emissions
GHG emissions reduction = 1 − proposed emissions ÷ baseline emissions. Each design’s emissions are each fuel’s annual site energy times its emission factor, added up.
- Electricity uses the CO₂e factor of the project’s EPA eGRID 2022 subregion, chosen under General Information, as in the LEED Minimum Energy Performance Calculator. Without a subregion, the US average applies; outside the US and Canada, the country’s national average.
- Canada: choose the province or territory in the same field. Electricity uses the calculator’s factor for it, below, and natural gas 116.4 lb CO₂e per MMBtu. The conclusion asks for the province or territory first.
- Other fuels, in lb CO₂e per MMBtu: natural gas 117.8, propane 139.1, fuel oil and diesel 163.6, gasoline 155.3, coal 209.4, district heating 147.3, district cooling 116.9. Fuel oil and diesel entered in gallons count 137.381 kBtu per gallon at the same factor, about 22.5 lb per gallon.
- Subtracted from the proposed design: on-site renewable energy and exceptional calculation savings at their fuel’s factor, and new off-site renewable energy at its grid region’s factor. Off-site renewable energy counts for this metric only.
Canada’s electricity factors, in lb CO₂e per MMBtu:
| Province or territory | Factor | Province or territory | Factor |
|---|---|---|---|
| Alberta | 403.0 | Nunavut | 520.0 |
| British Columbia | 8.5 | Ontario | 18.2 |
| Manitoba | 0.8 | Prince Edward Island | 156.0 |
| New Brunswick | 156.0 | Quebec | 1.2 |
| Newfoundland and Labrador | 16.3 | Saskatchewan | 403.0 |
| Nova Scotia | 117.0 | Yukon | 71.5 |
| Northwest Territories | 448.5 |
Unmet load hours
SimReader and InverseHub show the heating and cooling unmet load hours of each design, from the first file of each list. They flag a total over 300 hours in red.
Units
SimReader converts every report to the same units before any calculation. See SimReader units.