Heat Pump Research Project

Sponsored by the

Heat Pump Working Group

April 5, 2005

CheckMe!® Billing Analysis

Project Goal: Evaluate impact of refrigerant charge separately from CheckMe!® tune up.

Sample Distribution and Attrition

Raw Data Received

Complete Data

Analysis Set

Participants 598 334 322

Non-Participants 372 131 80

Participants were dropped if any one of several factors was noted:

•Customer turnover •Otherwise incomplete billing records•Participant record included a comment of “withdrawn”.

Analysis Methodology

• Weather-normalized pre- vs. post-consumption methodology

• Same difficulties using PRISM® as in C&RD analysis (wood heat, missing data, a/c).

• Used a simplified engineering model, EZSim®

• Initial plan to use “Test Only” group as control for comparison failed due to similar savings

• Group of 80 non-participants used as comparison instead

Fit of Model to Bills Example

Analysis Results: Savings Estimates

Analysis Results: NAC Difference (kWh/hr)

Group Mean StdDev

n 90% C.I. t-test

Refrigerant Adjust 310 3,410 100 677 0.92Test only 508 2,585 183 379 2.66Adjust plus repair 553 2,757 20 1,223 0.90Repair only 265 2,582 19 1,175 0.45All Participants 446 2,875 319 319 2.77

Note: Grayed rows indicate statistical significance.

Distribution Profile

Control Group Consumption

Note: n=80 2001 2002 2003Mean NAC 13,084 13,629 12,913

SD 5,330 5,231 5,415

90% Conf Interval 981 963 996

Annual Change -545 716

Average Change 86

Conclusions

• EWEB’s CheckMe!® program provides an effective average savings of 360 annual kWh. These savings are small but statistically significant.

• There are no additional savings associated with refrigerant adjustment. The savings appear to result from improvements made by the technician during the course of testing and examining the unit.

C&RD/ConAug Billing Analysis

Project Goal: Evaluate realization of anticipated savings from C&RD and ConAug heat pump programs in various climates.

Sample Distribution & Attrition

Group Region Expected Received Complete AnalyzedTreated TriCities 834 551 514 472

NW, Kitsap 749 638 533 383Central OR 481 121 124 96Coast 502 194 194 134Portland 403 403 300 279C&RD 1,521 1,009 808 740Non-C&RD 967 777 733 528Total 2,488 1,786 1,541 1,268

Untreated TriCities 250 167 167 154NW, Kitsap 249 251 225 81Central OR 209 124 124 96Portland 39 37 12 11Total 747 579 528 342

Reasons for High Attrition

• Billing procedural change at utility• Data collection change (Energy Trust)• Partial vacancy• Occupant turnover• Incomplete data

Billing Analysis Methodology

• PRISM® Regression – Proved Impractical Wood Heat Air Conditioning Missing data

• Multivariable Regression – Successful Regression run over range of balance

temperatures Balance temperature optimized for both years

together Individual case review for outliers

Heating Only Temperature Regression Example

Heating / Cooling Temperature Regression Example

Billing Analysis Results

• Statistically significant (with 90% C.I.)• Normalized annual data robust• Space heat, cooling and base load

disaggregation less robust• Little difference between C&RD & non-C&RD

groups• Tri-Cities represents the only cooling zone

Normalized Annual Consumption (NAC)

By Region By Equipment Type

Savings Estimates by Region

NAC 90% C.I. Est. Space Heat Use

90% C.I.

TriCities 3,795 492 3,197 338

NW, Kitsap 5,100 587 3,789 463

Coast 3,985 927 3,780 772

Portland 4,380 768 4,373 736

C&RD 4,354 328 3,620 255

Non-C&RD 3,851 626 3,803 477

Total 4,263 292 3,653 226

Savings Estimates by Equipment Type

System Type NAC Savings (kWh/yr)

90% Confidence Interval

Heat Pump 4,810 928

Forced Air FurnaceWith Central AC

2,979 825

Forced Air FurnaceWithout Central AC

4,625 603

Zonal 5,362 1,023

All Sites 4,263 294

Disaggregation

Normalizing VariablesCity HDD CDD

Richland 4,828 883Pt. Angeles 5,671 28Hoquium 5,164 31Astoria 5,116 18Portland 4,520 346Not C&RD 4,520 346Weighted AverageC&RD Group 5,203 343Total Study 5,091 344Cool 1 5,191 137Cool 3 4,828 883C&RD Cool 1 5,008 320C&RD Cool 3 5,008 990

System SF 90% CI

Heat Pump 2,193 129

FAF w/CAC 2,126 155

FAF no CAC 2,106 74

Zonal 2,121 164

All Sites 2,012 45

Vintage Bin Svgs (kWh/yr)

90% CI

Pre 1988 4,722 460

1986-1993 4,051 645Post 1993 4,140 1,080Average 4,263 294

Control Group Consumption

Note: n = 342 2001 2002 2003Mean NAC 20,160 20,467 19,932

SD 8,712 8,096 8,036

90% Conf Interval 775 721 715

Annual Change -307 535

Average Change 114

Realization Rates by Program Year Base

Prog Year

Area n Gross NAC

kWh/yr

Net NAC

kWh/yr

90% CI Antici-pated

kWh/yr

RR

2003 Cool 1 518 4,698 4,584 490 7,288 63%

Cool 3 318 3,795 3,681 590 6,815 54%

All C&RD 836 4,354 4,240 382 7,108 60%

Realization Rates by Region

Conclusions

• Study population was smaller than expected due to inability to obtain all the requested data. However, the study group of 1,022 cases is large enough for a relative precise estimate of mean savings. Breakdown of estimates into subsets of the study population suffers from missing information and small sample size for sub-categories.

• Best estimate of net savings is 4,149 kWh per year and is highly significant. Best estimate for only the C&RD participants is 4,240 kWh per year.

Conclusions (continued)

• Savings are approximately 60% of the predicted amount. There is ambiguity because specific ex ante savings estimates are not available.

• There is little difference in overall savings between climate zones. However, Cooling Zone 3 exhibits more cooling consumption and savings, as would be expected.

• There are significant differences between the type of equipment that was replaced. These differences do not show higher savings for furnace over zonal, as would be expected. The equipment codes also appear to be highly unreliable. Thus, no conclusions are suggested based on equipment type.

Purdue University Lab Tests

Project Goal: Establish the charge in heat pump performance resulting from sub-optimum refrigerant charge and air handler flow.

TXV and FEO Comparison

• Biggest impact in higher temperature bins 47° shows a 10% degradation with FEO & 5%

with TXV• Much smaller impact in lower temperature

bins.• At some temperature point, performance is

actually degraded by TXV and lower charge variation

TXV vs. FEO System at 47° F

2.62.652.7

2.752.8

2.852.9

2.953

3.05

60% 70% 80% 90% 100% 110% 120% 130% 140%

Charge of Norminal [%]

COP

at 4

7 F

TXV

FEO

Comparison of COPs of TXV system and FEO system at 47 F outdoor temperature , 1300 indoor CFM and different charges

TXV vs. FEO System at 35° F

Comparison of COPs of TXV system and FEO system at 35 F outdoor temperature , 1300 indoor CFM and different charges

2.52

2.54

2.56

2.58

2.6

2.62

2.64

2.66

2.68

60% 70% 80% 90% 100% 110% 120% 130% 140%

Charge of Norminal [%]

COP

at 3

5 F

FEO

TXV

TXV vs. FEO System at 17° F

Comparison of COPs of TXV system and FEO system at 17 F outdoor temperature , 1300 indoor CFM and different charges

1.982

2.022.042.062.082.1

2.122.142.162.18

60% 70% 80% 90% 100% 110% 120% 130% 140%

Charge of Norminal [%]

COP

at 1

7 F

TXV

FEO

Impact of Different Charges and Temperatures on COP

1.5

1.7

1.9

2.1

2.3

2.5

2.7

2.9

3.1

60% 70% 80% 90% 100% 110% 120% 130% 140%

Charge of Norminal [%]

COP

of H

eat P

ump

usin

g TX

V

17 F

35 F

47 F

COP of heat pump using a TXV at 1300 CFM indoor air flow rate, different charges and outdoor temperatures

Impact of Frost Formation on Heating Capacity

Degradation of heating capacity due to frost formation

81%82%83%84%85%86%87%88%89%90%91%92%

700 900 1100 1300 1500 1700

Indoor Air Flow Rate [SCFM]

Degr

adat

ion

Ratio

in H

eatin

g Ca

paci

ty [%

]

70% charge

100% charge

130% charge

Impact of Frost Formation on COP

Degradation of COP due to frost formation

85%86%87%88%89%90%91%92%93%94%

700 900 1100 1300 1500 1700

Indoor Air Flow Rate [SCFM]

Degr

adat

ion

Ratio

in C

OP

[%]

70% charge

100% charge

130% charge

Lab Tests: Preliminary Results

• Degradation of COP for TXV and FEO will be less than that seen at 47°.

• Impact of defrost is potentially significant, although low charge seems to improve performance

• CD tests more inclusive, but results seem to suggest higher values than those used in tables.