Since 1993 BPI has developed industry standards that foster quality and consistency throughout the nation’s home performance and weatherization workforce. BPI standards are periodically updated in response to advancing knowledge and industry needs and are freely available for use.

BPI-2400 is the Standard Practice for Standardized Qualification of Whole-House Energy Savings Predictions by Calibration to Energy Use History (Delta Standard). It specifies the requirements and process for the calculation of standardized predicted savings using approved building energy simulation software and the actual energy usage of the building.

BPI-2400 is referenced in the HOMES Energy Efficiency Rebate Program, part of the Inflation Reduction Act of 2022 (IRA).
In an effort to ensure that public monies achieve the desired results, the legislation specifies that State Energy Offices to use “procedures…for determining the reductions in home energy use resulting from the implementation of a home energy efficiency retrofit that are calibrated to historical energy usage for a home consistent with BPI-2400, for purposes of modeled performance home rebates.”

Understanding BPI-2400

Like all BPI standards, The Delta Standard was developed by a working group of Subject Matter Experts (SMEs), representing a wide variety of interest categories and geographical locations, in a consensus-based process.

This standard specifies a process to calibrate the model to the actual energy use of the home, using an approved building energy simulation software tool and actual energy bills. It provides a set of criteria to be used in the final calculation of standardized estimated savings that may be considered in compliance with this standard. 

Coming Changes for BPI-2400

BPI-2400 will be reviewed by SMEs in early 2023 to ensure the standard meets industry needs related to the IRA. The current standard specifies 12 months of good data on energy usage for calibration. Unfortunately this information is not always available, as when homeowners have owned their homes less than 12 months, do not retain good records on usage of delivered fuels, or when data on connected fuel usage from utilities is not available, or is not available in clean, usable formats.

The review will likely provide a proposed alternative pathway to compliance when good data is not available; no new requirements will be added to the standard. There will be clear indications for the alternative pathway’s use to ensure that all preferred sources of highest-quality data are explored before it is used.

How Additions to Standards are Made

As a standards organization BPI convenes Standards Technical Committees of industry professionals, facilitates and records meetings, and hosts and maintains approved standards. Standards are supported and written by all-volunteer working groups from under the direction of the Standards Technical Committee and approved by the whole. BPI's Data and Modeling Standards Technical Committee (DM-STC) will be reconvened to develop and approve the additions.

Results to Expect

The additions will allow software vendors to develop products that meet the need of both contractors and program administrators of the IRA Funds. Contractors will be able to model the results of home performance retrofits with ease. States will gain confidence that the information on retrofit results is accurate and reliable.

Additions will also advance energy equity by allowing homeowners to access rebates regardless of fuel source, who may have previously been barriered by lack of reliable data.

BPI standards are freely available for use. Current standards may be found here. Standards under review may be found here. Watch this space for further news on the update to BPI-2400.