M e m o r a n d u m
FROM:
Jeff Romberger, SBW
TO:
Mark Kendall
DATE:
February 15, 2012
RE:
Deemed Measure Detail Review and Update Recommendations: Residential DHW –
Efficient Tanks
CC:
Tom Eckman, Charlie Grist and Adam Hadley
This memo documents the results of KEMA’s detailed review of the deemed measure category
Residential DHW – Efficient Tanks. This measure category covers savings from installation of efficient
electric storage water heaters between 25 and 120 gallons in new or existing residential sectors. KEMA
reviewed the RTF supplied file ResDHWFY10v2_1.xls. The review focused on the measures tabulated on
the “MeasureTable” worksheet and the derivation of those measures’ Unit Energy Savings (UES).
Summary Recommendation. This measure category should be classified under review. The measure
sunset criteria should be changed to March 2013 (at which time new data should be used to develop the
baseline and efficient-case EF values). In addition, there are minor workbook structure and
documentation improvements that should be made. Once these have been implemented or resolved,
the measure can be returned to the classification active.
Limitation of Review. None
Additions to Workbook Documentation.


A sheet called “Summary” has been added to the workbook. This sheet describes how measures
are identified, lists important constants and their sources, describes the savings estimation
algorithm and the associated baseline and efficient case parameters and their sources for each
measure and UES component.
A note was added on the “Cost – Residential” spreadsheet (Cell BZ20) to clarify the measure
threshold efficiencies (“Cost – Residential” spreadsheet cells BZ21:BZ27) are arbitrary and based
on RTF judgment.
Workbook Calculation Errors. No calculation errors were found.
2820 Northup Way, Suite 230
Bellevue, WA 98004
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Recommendations for Updates. The RTF should consider the following findings and recommendations
for additional updates:
1) Workbook Structure and Formulas
a) Consider removing material and worksheets related to commercial water heaters. Worksheets
that have both residential and commercial specifications (e.g., “Federal Standards” and “EF to
Standby Loss” worksheets) can have commercial related material removed. Commercial-specific
worksheets like “AHRI Comm Data”, “CBSA analysis for interactions”, and “6th plan lighting
Interactions” can be removed without affecting the residential measures’ UES or
documentation.
b) Consider repairing the broken links on the “EF to Standby Loss” worksheet; or as an alternative,
consider moving the Water Heater Analysis Model reference and equation material to the
“Constants and Assumptions” worksheet and removing this worksheet entirely.
c) Consider removing the “Measure Specifications” and “HVAC Interactions” sections on the
“Constants and Assumptions” worksheet. They appear to be unused in the workbook and create
inconsistencies in documentation, specifically with the electric net heating and cooling
interactions and the residential “deltaEF”.
2) Documentation
a) Document the assumed water heater rated input power (Pon) used to calculate hourly standby
losses from the Water Heater Analysis Method (WHAM) standby heat loss coefficient equation.
The rated input power assumed in the workbook is 4.4 kW1.
b) Document the date that the AHRI dataset was retrieved and introduced in to the workbook. This
is important to estimate the vintage of the water heaters being used from that dataset in order
to develop baseline and measure standby heat losses (i.e., EF values).
3) Measure Definition
a) No changes recommended
4) UES Savings Estimation Method
a) No changes recommended
5) Input Parameters
1
A PowerPoint presentation given to the RTF June 1, 2010 shows that the 4.4 kW power rating comes from
the “average of all residential electric storage units in AHRI directory”.
http://www.nwcouncil.org/energy/rtf/meetings/2010/0601/
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a) The current datasets used for baseline and efficient case EF values should be reviewed and
updated in 12 months (March 2013). The 2008 Summit Blue data will be five years old and will
no longer represent the current regional market availability of electric water heaters. Explore
the following options for updating the datasets used for EF values:
i)
Use an updated AHRI dataset exclusively for EF values rather than a mix of the two datasets
currently used (a possibly outdated AHRI dataset and a 2008 Summit Blue regional in-store
DHW dataset). An AHRI dataset is already part of the baseline and measure average EF mix
and the Summit Blue in-store dataset may be outdated and will no longer appropriately
represent the regional market. An updated AHRI dataset is a reasonable replacement of the
in-store data to estimate the baseline and efficient-case market weighted average
efficiencies.
ii) Consider performing another regional in-store data collection (Similar to the Summit Blue
study) study in order to update the baseline and efficient-case market-weighted EF values.
The sample size of the data collection should be larger (i.e., number of stores visited and
expand regional coverage) than the 2008 study in order to increase precision of the market
average for each size range, but to also capture the low and high tank volume ranges that
the current workbook has to supplement with AHRI data.
b) Another sunset period should revolve around new federal standards for electric storage water
heaters that will become effective April 16, 2015.2 The dataset should be reviewed and updated
again to ensure that average baseline and efficient case EF values reasonably represent available
market efficiencies.
2
Federal Register Volume 75, No. 73. April 16, 2010 (10 CFR Part 430)
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