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Energy Consumption of Major Household Appliances Shipped in Canada – Trends for 1990-2003


Appendix A - Methodology

A.1  Data Preparation

A.1.1  Introduction

In an ongoing effort to improve the monitoring of trends in Canadian energy use, Natural Resources Canada’s (NRCan’s) Office of Energy Efficiency (OEE) proposed an annual data collection arrangement with members of the Canadian Appliance Manufacturers Association (CAMA) in 1996, as part of the National Energy Use Database (NEUD) initiative.

Under this agreement, CAMA members contributed their annual shipment data for six appliance categories – refrigerators, freezers, electric ranges, dishwashers, clothes washers and electric clothes dryers – for analysis. To keep each appliance manufacturer’s data confidential, appliance manufacturers suggested that a third party receive and prepare the database in a format in which no one (other than the third party) could determine the shipment data for an individual model or manufacturer. NRCan retained the services of Electro-Federation Canada (EFC), chosen by CAMA, as the third party to receive the data.

The following sections describe the database preparation process conducted by EFC.

The data presented in this report combine shipment figures from the major appliance manufacturers in Canada with the energy use information contained in NRCan’s annual EnerGuide Appliance Directory. Analysts from EFC matched the model number from the manufacturer with the corresponding model in the EnerGuide Appliance Directory. Thus, they arrived at the total energy consumption represented by all shipments of that model within each year. They aggregated these figures to provide the data presented in this report.

The analysts used the standard database and spreadsheet software to assemble the data, manipulate it as required and return it to NRCan for analysis and report generation. (For the reporting stages, the analysts stripped all data of any information that could identify the manufacturer or the model number.)

A.1.2  Manufacturers’ Data

NRCan sent initial letters to the appliance manufacturers, requesting annual shipment data for each model of refrigerator, freezer, electric range, dishwasher, clothes washer and electric clothes dryer on the Canadian market from 1990 to 2003. When the project began in 1996, only three manufacturers provided shipment data. The number of data contributors increased to eight in 2003, covering the vast majority of appliance models sold in Canada.

Manufacturers sent the data in various electronic and printed formats. EFC converted the electronic data to a common database format. The analysts key-edited the printed reports and then converted them to the same format.

The data consisted of the appliance type, model number and number of shipments in each year. Manufacturers supplied individual files for each year. As each manufacturer provided data in a different format, the analysts harmonized and amalgamated the files to produce a single file for all models by appliance type and model year.

The nature of the freezer market prevented EFC from obtaining a model-by-model breakdown of shipments. Instead, the analysts received total shipments and average energy use by freezer type. NRCan used this information to generate the freezer reports.

A.1.3  EnerGuide Data

The analysts used the size, type and unit energy information from NRCan’s EnerGuide ratings for each appliance to calculate the shipment-weighted energy use of each appliance type.

A.1.4  Data Matching

Analysts from EFC matched the manufacturer’s data for each model with the corresponding energy consumption data from the EnerGuide Appliance Directory for that model. They then multiplied the manufacturer’s shipments for each model by the corresponding EnerGuide model’s energy rating. This gave the shipment-weighted total energy consumption for that model. Each appliance category (e.g. refrigerator, dishwasher) and type and size category (as defined in the EnerGuide books) was then subtotalled so that the average consumption could be worked out.

The EnerGuide Appliance Directory shows the basic model numbers available on the Canadian market. Many slight model variants have the same energy rating, so the listings use symbols (such as * and #) to indicate model families. As some model numbers have additional prefixes or suffixes to indicate features (e.g. colour, door-swing) that do not affect energy use, there were relatively few direct one-to-one matches.

Analysts needed to manipulate the data to perform pattern matching. They wrote programs to compare the model numbers supplied by the manufacturers with those in the EnerGuide Appliance Directory. When a match was found, the corresponding energy consumption figure and the information on the type from the EnerGuide Appliance Directory were added to the record for the annual shipments of the model.

Because there were many combinations of character substitution, the analysts adopted a method to work from the closest matches to the least likely matches. Matches in which only one character differed were flagged and removed. Attempts were then made with a difference of two characters, and so on.

The analysts developed reasonability tests to ensure the integrity of the data-matching process. For example, if the manufacturer’s model number contained many characters but was matched by a model in the EnerGuide Appliance Directory that had considerably fewer characters, the model was flagged for manual checking. They also realized that manufacturers might re-use the same numbers for different models after several years. For example, 128 models of refrigerators in the file containing 1980 to 1993 data from the EnerGuide Appliance Directory have the same model number as those in the 1997 file, but with different energy ratings. They flagged these models for special treatment. During the matching process, analysts applied a "reasonability" criterion: a model would be checked manually if its shipments were reported more than three years after the last time the corresponding model appeared in the EnerGuide list.

Some difficulties occurred when the model number in NRCan’s EnerGuide Appliance Directory differed from the actual model numbers used by the manufacturers in their internal shipment recording systems. In some cases, for example, manufacturers used special codes to denote models that were branded for other companies (such as department stores). The manufacturers helped resolve most of these cases.

A number of models remained unmatched even after the automated processes were performed. Whenever one of these models represented a substantial number of shipments for that appliance type, analysts handled it on an exceptional basis. Manufacturers were again helpful in the identification of these models and the verification of energy ratings and types.

The process continued until all but a few minor models were matched.

A.1.5  Data Summary and Transfer

After the matching process, analysts summarized the data. To calculate the total annual energy consumption for each model, they multiplied the energy rating of the model by the number of shipments for the year. This yielded the shipment-weighted total energy used by that model for that year. For example, model XYZ has annual shipments of 5238 and an annual energy consumption of 683 kilowatt hours (kWh); its shipment-weighted total energy use for the year is 5238 x 683 = 3 577 554 kWh. This aggregate figure and the shipment figures were added as necessary to provide totals for appliance and type and size category as appropriate for each appliance type.

For refrigerators, the actual volume of each model was available from the EnerGuide Appliance Directory. Therefore, it was possible to monitor the trend of changes in the size of refrigerators over the years. Furthermore, it was possible to determine the amount of energy used by each size category. Analysts also summarized this information and added it to the database for NRCan.

The final database prepared by EFC consisted of such information as the appliance type, model year, total energy consumption and average unit consumption. Refrigerators were further categorized by type and size. All the information was transferred to a spreadsheet and sent to NRCan for analysis and reporting.

A.2  Analysis

The shipment-weighted average annual unit energy consumption (UEC) by category was calculated as total energy consumption of all the refrigerators sold in Canada in that category divided by total number of shipments in that category. The following gives an example of the shipment-weighted average energy consumption for the refrigerators:

Example of the shipment-weighted average energy consumption for the refrigerators.

As mentioned in the "A.1 Data Preparation" section, data were obtained for some appliances by size category. Therefore, unit energy consumption per cubic foot was calculated by dividing the UEC of a given size category by the midpoint of the category.

Calculating the incremental energy savings for each appliance type involved a three-step process.

  1. Baseline levels of energy consumption were estimated for each appliance type for each year between 1990 and 2003. For all appliances, baseline levels of energy consumption reflected our assumptions about how much energy each appliance type would have consumed without the energy efficiency improvements made by manufacturers and the minimum energy performance standards (MEPS). To estimate baseline levels of energy consumption, we assumed the following:

    • Without the implementation of Canada’s Energy Efficiency Regulations and general energy efficiency improvements made by manufacturers, the UEC for all appliance types would have remained constant at the 1992 levels.

    • The number of units shipped would have remained the same between 1990 and 2003 even in the absence of the general efficiency improvements made by manufacturers and the implementation of the Energy Efficiency Regulations.

Even though the MEPS were not introduced until 1995, the baseline year used for all estimates of energy savings was 1992. This is because energy efficiency began to improve almost immediately after the Energy Efficiency Act came into force in 1992, thanks to market forces such as the regulations expected from the Act and U.S. regulations.

  1. "Actual" or current levels of consumption for all appliances were calculated in an identical fashion. The average annual unit energy consumption for each appliance type for each model year was used, instead of holding it constant at 1992 levels, to determine the actual levels of energy consumption.

  2. Incremental energy savings for all appliances were then calculated as the difference between baseline and actual levels of energy consumption.