Performance Cost Index: Multi-Metric BPF Support
Better Building's Performance Cost Index workflow now supports three additional compliance metrics alongside energy cost: site energy, source energy, and greenhouse gas emissions.
The structure of the PCI workflow hasn't changed. What's new is that the Building Performance Factor your result gets compared against can now be expressed in whichever of those four metrics your jurisdiction requires.
This matters because the cost-only PCI has a structural problem that's become harder to ignore as decarbonization goals show up in actual energy codes. Natural gas is cheaper per BTU than electricity in most of the country, so cost-based compliance quietly favors fossil fuel systems. A building can score perfectly fine on cost while running a noticeably dirtier energy profile than an all-electric alternative. Supporting carbon and source energy metrics is the practical fix for that. Better Building currently supports ASHRAE 90.1-2019 only.
A Quick Refresher on BPFs
The PCI compares your proposed building's energy use against a code-compliant Appendix G baseline, and the Building Performance Factor is the threshold that comparison has to meet or beat. It's not one number for every building. BPFs vary by building area type and climate zone because an office building and a warehouse have wildly different energy profiles even when both hit the same level of code compliance.
The BPF values in ASHRAE 90.1 Table 4.2.1.1 use national average utility rates and emissions factors. Reasonable defaults, but averages nonetheless. If your jurisdiction has a significantly cleaner grid, higher electricity prices, or a local carbon accounting requirement, those averages can produce thresholds that don't reflect where your projects actually sit. This update lets jurisdictions supply local conversion factors and generate BPFs calibrated to local conditions.
Custom BPF values require approval from the Authority Having Jurisdiction or Rating Authority before use. The national defaults are pre-populated and don't require any additional approval.
The Four Metrics
Energy cost is what the PCI has always done. It remains the default and the most widely accepted metric for Appendix G compliance.
Site energy is raw BTUs at the building, no conversion factors, no upstream accounting. It treats a kWh of electricity the same as a BTU of gas regardless of how that electricity was generated. Simple, auditable, and admittedly a bit blunt.
Source energy works upstream, applying multipliers that account for power plant inefficiency and transmission losses. The default electricity factor is 9.008 kBtu/kWh, derived from EIA data, which is why source EUIs always look alarmingly high next to site EUIs. It's not wrong. It's just accounting for the full chain.
Greenhouse gas emissions converts consumption to CO2-equivalent using fuel-specific factors. Defaults are 1.2 lb CO2e/kWh for electricity and 19.96 lb CO2e/therm for natural gas (both from EPA). This is the metric most sensitive to local inputs. Regional electricity emissions vary by a factor of five or more across the U.S., so a jurisdiction with access to eGRID subregional data will get meaningfully different carbon BPFs than one using the national average. That's the point.
BPF Approach: "As Published" vs. "New Approach"
When calculating custom BPFs, you choose between two sets of underlying prototype simulation results.
"As Published" reproduces the prototype results used when 90.1-2019 was developed. Here's the part that always gets a reaction: the published 90.1-2019 BPFs are based on prototype models originally built for 90.1-2004. True Appendix G baseline prototypes weren't available when the 2019 edition was finalized, so they used what existed. It's a historical artifact, not a modeling error. Choose this if you need to reproduce Table 4.2.1.1 exactly or maintain backward compatibility with prior submissions.
"New Approach" uses updated Appendix G baseline prototypes that follow the Appendix G baseline rules as currently written, including corrections made after the 2019 edition was published. These come from the PNNL Technical Support Document on 90.1-2019 Appendix G PRM prototypes. If you're building a new jurisdiction compliance program, this is the more defensible choice. The PNNL authors say directly that they consider it more technically sound, and based on the underlying work, that's a fair assessment.
Inputs
All conversion factor inputs represent annual blended averages. Where a jurisdiction requires time-of-use or hourly pricing data, calculate the annual average externally and enter that single value. Annual energy models don't optimize dispatch against time-varying rates, so a blended figure is the right input regardless of how your utility structures its bills.
Conversion Factor Units by Metric
Energy cost
$/kWh
$/therm
Source energy
kBtu/kWh
kBtu/therm
GHG emissions
lb CO2e/kWh
lb CO2e/therm
If the project uses fuels other than natural gas, enter equivalent values in the same units.
Default Conversion Factors (90.1-2019)
Pre-populated in the workflow. To reproduce Table 4.2.1.1 exactly, use these cost values with the "As Published" approach.
Electricity
kWh
1.2
9.008
$0.1063
Natural gas
Therm
19.96
109.0
$0.98
How the Calculation Works?
The BPF for a building type and climate zone is the average proposed-to-baseline regulated energy ratio across all prototypes of that building type:
Np is the number of prototypes for that area type. This applies to all four metrics. You're just swapping in site energy, source energy, cost, or carbon as the unit of measure.
When you supply local conversion factors, BPFs are recalculated using pre-computed site energy coefficients (A, B, C) from the prototype models. No simulation reruns needed:
EC is your electricity conversion factor, GC is your gas conversion factor, and the coefficients are looked up by building area type i and climate zone j. The three coefficients encode the fuel mix ratios from the prototype simulations, all normalized to the proposed electric site EUI:
A
Proposed regulated gas site EUI / Proposed regulated electric site EUI
B
Baseline regulated electric site EUI / Proposed regulated electric site EUI
C
Baseline regulated gas site EUI / Proposed regulated electric site EUI
Because everything is expressed relative to proposed electric EUI, any combination of electricity and gas conversion factors produces a valid BPF from the same underlying data. It's a small piece of elegant math in a standard that doesn't always have a lot of it.
Published BPF Reference Values (90.1-2019)
Selected climate zones shown below. Full 19-zone tables are in PNNL TSD Tables 50, 51, and 52.
Site Energy BPFs
Multifamily
0.76
0.76
0.76
0.69
0.71
0.68
0.67
0.67
Healthcare/Hospital
0.71
0.74
0.72
0.71
0.72
0.74
0.73
0.80
Hotel/Motel
0.75
0.74
0.75
0.76
0.75
0.74
0.72
0.72
Office
0.61
0.58
0.57
0.55
0.55
0.59
0.59
0.54
Restaurant
0.65
0.64
0.66
0.68
0.72
0.76
0.78
0.79
Retail
0.53
0.48
0.47
0.48
0.59
0.66
0.67
0.60
School
0.58
0.55
0.57
0.50
0.47
0.53
0.54
0.52
Warehouse
0.24
0.23
0.27
0.19
0.40
0.49
0.52
0.46
All Others
0.66
0.59
0.58
0.61
0.61
0.64
0.66
0.64
Source Energy BPFs
Multifamily
0.72
0.72
0.70
0.61
0.70
0.68
0.69
0.68
Healthcare/Hospital
0.73
0.74
0.72
0.71
0.72
0.74
0.73
0.77
Hotel/Motel
0.72
0.70
0.70
0.70
0.70
0.70
0.69
0.68
Office
0.61
0.58
0.57
0.55
0.56
0.58
0.57
0.55
Restaurant
0.62
0.61
0.61
0.61
0.65
0.68
0.70
0.72
Retail
0.53
0.48
0.47
0.47
0.50
0.54
0.55
0.51
School
0.57
0.55
0.57
0.48
0.48
0.51
0.52
0.51
Warehouse
0.24
0.23
0.27
0.20
0.30
0.36
0.40
0.37
All Others
0.64
0.57
0.56
0.57
0.58
0.59
0.60
0.60
Carbon BPFs
Multifamily
0.73
0.73
0.72
0.63
0.70
0.68
0.68
0.68
Healthcare/Hospital
0.73
0.74
0.72
0.71
0.72
0.74
0.73
0.78
Hotel/Motel
0.73
0.72
0.72
0.72
0.72
0.72
0.70
0.70
Office
0.61
0.58
0.57
0.55
0.55
0.58
0.58
0.54
Restaurant
0.63
0.62
0.63
0.63
0.67
0.71
0.73
0.74
Retail
0.53
0.48
0.47
0.47
0.53
0.58
0.59
0.54
School
0.58
0.55
0.57
0.49
0.47
0.51
0.53
0.51
Warehouse
0.24
0.23
0.27
0.20
0.33
0.41
0.44
0.40
All Others
0.64
0.58
0.57
0.58
0.59
0.61
0.62
0.61
Last updated
Was this helpful?