Residential EE Methodology

The general methodology for all energy efficiency measures can be found here. The sections below provide an overview specific to the residential sector.

Overview of Methods for Residential Sector

For the residential sector measures, most measures apply to a fraction of the building stock in a particular building type. For example, insulation measures are a function of the number of households with electric heat, refrigerator efficiency improvements are a function of the number of refrigerators that are replaced or purchase new each year, and the potential savings from heat pump water heaters are function of the number of homes with electric water heating. Details by measure can be found in the measure workbooks.

For every measure or practice analyzed, there are major methodological steps to go through establish number of units, baseline conditions, measure applicability, and measure achievability. For the residential-sector conservation measures, each of these is treated explicitly for each measure bundle.

One of primary inputs into the residential sector conservation assessment is the number of units that each conservation measure or measure bundle could be applied to in the region. Space conditioning savings are a function of both the characteristics of the structure and the climatic conditions where the home is located. Therefore, the Council’s assessment includes estimates of the number of new and existing dwelling units of each type (i.e., single family, multifamily, manufactured homes) in nine different climate zones. The Council defines climate zones by specific combinations of heating and cooling degree days. The table below shows the nine climate zones in the region, more information can be found on the RTF climate zones webpage.[1]

Regional Heating and Cooling Climate Zones

Physical Units for Residential

The conservation supply curves are developed primarily by identifying savings and cost per unit and estimating the number of applicable and achievable units upon which that the measure can be deployed. In the residential sector analysis, the applicable unit estimates for space conditioning, water heating, lighting, and appliances are based on the number of existing housing units and forecast of future housing growth from the Council’s Demand Forecasting Model. The housing units from the forecasting model were allocated to climate zones based on the population weighted average heating and cooling degrees for each county in the region. The housing unit data by state are contained in the Excel workbook entitled “2021P Forecasts.xls.” The estimates of physical units available include the number of units available annually. For example, for new buildings, the estimate of available new building stock is taken from the Council’s baseline forecast for annual additions by building type. Similarly, for equipment replacement measures the annual stock available is taken from estimates of the turnover rate of the equipment in question. For retrofit measures, the annual stock availability is a fraction of the estimated stock remaining at the end of the forecast period. Most of the unit saturations are from the 2016-2017 Residential Building Stock Assessment (RBSA), which provided a detailed analysis of homes across the region. These are incorporated into the individual supply curve workbooks as applicable. In addition, much of these data are also in the “Res_Master2021P.xls” workbook.

Residential Baseline Characteristics

Baseline conditions are estimated from current conditions for existing buildings and systems. Estimates of current conditions and characteristics of the building stock come from several sources. Key among these are the market research projects of NEEA, selected studies from utilities, Energy Trust of Oregon, and other sources, details are available in the individual measure workbooks.

For new buildings and new and replacement equipment, baseline conditions are estimated from a combination of surveys of new buildings, state and local building energy codes, and federal and state appliance efficiency standards. The RBSA, completed in 2017, is the source for saturations of most equipment and appliances.

Baseline characteristics for major appliances (washers, dishwashers, refrigerators, and freezers) are based on sales data collected by NEEA or, if those are not available, based on the products available in the equipment appliance database from the California Energy Commission. Cost data for appliances was obtained from NEEA or an analysis of the utility programs and Internet searches. Heating, cooling, insulation, and window cost were obtained from an analysis of program data from Puget Sound Energy and the Energy Trust of Oregon. The assumptions were often tied to those determined by the RTF in its development of unit energy savings.

Residential Measure Applicability and Achievability

There are hundreds of applicability assumptions in the residential-sector conservation assessment. Applicability assumptions by measure appear in the Res_Master workbook. The baseline saturation is provided in tab “BASE”, the technical feasibility is provided in the tab “FEAS”. The final applicability (the product of FEAS * (1 - BASE)) is provided on tab “APPLIC”. For example, if BASE = 10 percent, and FEAS = 90 percent, the final applicability = 90%*(1-10%) = 81%.

The measure achievability is provided in the Res_Master workbook, tab “ACHIEV”. The overall ramp rates are given on the top of the sheet, with the selected ramp rate for each measure listed below. In addition, the maximum achievable provided in Column X for each measure.

Guide to Residential Workbooks

The tables below provide a cross-walk between the measures included in the Council’s assessment of regional conservation potential in the residential sector and the name of the individual measure and supporting workbooks. The most recent versions of these workbooks are posted on the Council’s website and are available for downloading.

Residential Sector Supply Curve Measure Workbooks

Residential Supporting Workbooks

All of the individual measure files are linked to the “Res_Master.xls” file. This file contains the complete measure list, baseline data, applicability factors, and ramp rates (achievability rates). The reference data in ResMaster are primarily in matrices by measure bundle and building type. The primary reference data in the ResMaster file are listed and described in the table below.

Reference Data in ResMaster Workbook

[1] Heating and cooling degree days are daily, base 65 deg F