Memorandum to: Scott Dimetrosky, eeb evaluation Consultant From



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Scope of Work


NMR developed IE factors for use in program savings calculations by:

  • Developing a REM/Rate model for each of the 180 sites in the sample that is identical to the as-built model except for a 25-bulb efficient lighting upgrade;

  • Calculating IE factors based on primary heating fuel and cooling configuration;

  • Calculating statewide electric and heating fuel IE factors.

Sampling


The same 180 single-family homes which NMR audited for the Weatherization Baseline Assessment were used to model interactive effects for the Lighting Interactive Effects study. The Baseline Assessment focused exclusively on single-family homes, both detached (stand-alone homes) and attached (side-by-side duplexes and townhouses that have a wall dividing them from attic to basement and that pay utilities separately). More details regarding the sampling plan for this study can be found in .

Analysis of REM/Rate Data


NMR incorporated lighting data which was gathered for the 2012 Connecticut Efficient Lighting Saturation and Market Assessment4 into each of the 180 REM/Rate models.5 Each model was assigned a number of bulbs consistent with the home’s size, and the bulbs were divided between inefficient and efficient6 types. Two models were developed for each of the 180 sites: a baseline or “as-is” model, and an upgrade model.

In order to create the upgrade models, the baseline models were altered by changing the wattages of a maximum of 257 of the inefficient bulbs to the average wattage of CFLs found in the Saturation Study. This is consistent with Home Energy Solutions (HES) program guidelines, which limit the number of efficient bulbs installed at any given home to 25.8 The HVAC impacts per bulb are the same regardless of how many bulbs are upgraded in the models, and therefore the IE factors are the same.


Peak Demand and Coincidence Factors


In order to assess peak demand savings, NMR used REM/Rate demand estimates as a starting point. After reaching out to Architectural Energy Corporation (AEC), the developers of REM/Rate, NMR determined that REM/Rate assumes coincidence factors when assessing peak demand. NMR removed these pre-existing coincidence factors and applied Connecticut-specific coincidence factors to provide a more accurate estimate of the peak demand impacts.

Table displays the coincidence factors applied in this study. The heating and cooling coincidence factors are from the 2013 Connecticut Program Savings Documentation.9 The factors for lighting are taken from a recent Northeast Residential Lighting Hours-of-Use Study conducted by NMR and DNV GL.10

Table : Peak Coincidence Factors11


End Use

Summer

Winter

Heating

0.00

0.50

Cooling

0.59

0.00

Lighting

0.13

0.20


Interactive Effects Factors


This section describes the four types of IE factor. Examples of how to adjust savings to account for interactive effects using these factors can be found in .

Electric Energy Interactive Effects


The electric IE factor is a unitless multiplier used to adjust electric savings from lighting retrofits to account for changes in space conditioning requirements.

  • For homes with no electric heating or cooling equipment, the electric IE factor will be equal to 1.0, indicating that lighting savings require no adjustment.

  • For homes with electric heating equipment, the factor is usually less than one—because Connecticut is in a heating-dominated climate, electric savings for cooling are generally less than the increased electric usage for heating associated with the lighting retrofit.

  • For homes with electric cooling equipment but non-electric heating equipment, the factor will generally be greater than 1.0, indicating that the electric savings resulting from the lighting retrofit will be greater than the savings achieved at the lighting end use alone.

The electric IE factor is calculated in the following manner:

Table describes the results of the electric IE factor analysis. Overall, the statewide electric IE factor is 1.04, meaning that CFL retrofits will actually result in 104% of the electric energy savings achieved at the lighting end use alone.

Table : Electric Energy IE Factors by Cooling Configurationa


Cooling configuration

Number of Homes

Avg

Min

Max

Overall

180

1.04

0.61

1.19

Central air conditioner

77

1.10

0.71

1.19

Room air conditioner(s)

68

1.04

0.61

1.14

Heat pump

13

0.96

0.63

1.12

No cooling

22

0.99

0.91

1.00

a Proportionally weighted to reflect statewide saturation percentage

of ducted central air conditioning systems—see Section .

Table presents electric IE factors by cooling configuration and heating fuel type. When electric heating equipment is absent or is not the primary heating mechanism in the home, the average electric IE factor is greater—about 1.07 vs. 0.73 for electrically-heated homes. Sites heated primarily with something other than electricity comprise 166 (92%) of 180 sites in the sample.

The electric energy IE factor is 1.0 among homes that heat with fossil fuels or biomass12 and have no cooling equipment, indicating that the electric savings due to lighting retrofits in these homes require no adjustment.

Table : Average Electric Energy IE Factors by Cooling Configuration & Heating Fuela


Cooling configuration

Overall

Primary Heating Fuel

Oil, LP, or Biomass

Natural Gas

Electric

Overall

1.04

1.07

1.08

0.73

Central air conditioner

1.10

1.1

1.11

0.71

Room air conditioner(s)

1.04

1.08

1.09

0.69

Heat pump

0.96

1.06

1.1

0.82

No cooling

0.99

0.99

1.00

-

Number of homes

180

118

48

14

a Proportionally weighted to reflect statewide saturation percentage of ducted

central air conditioning systems—see Section .


Electric Energy Impact Per Bulb


Table displays the additional electric savings due to interactive effects in annual kWh per upgraded bulb. The analysis shows that each efficient bulb replacing an incandescent bulb will result in 1.72 kWh/year in electric energy savings over and above the savings attributable to the new bulb itself. For homes with no electric heating equipment, those savings are greater—in these homes, lighting retrofits will result in extra savings of about 3 kWh/year per upgraded bulb.

In homes without electric heating equipment, interactive effects lead to each bulb realizing 108% of the electric savings attributable to the bulb by itself. In homes that primarily use electric heating equipment, however, interactive effects result in a bulb that only realizes 93% of its expected savings. Statewide, the analysis showed that each bulb upgrade results in savings of 104% of the savings attributable to the bulb itself due to interactive effects.

Table : Average HVAC Electric Energy Savings Per Upgraded Bulba


Cooling configuration

Number of Homes

Annual Extra Electric Savings in kWh/bulb

Overall

No Electric Heating

Has Electric Heating

Overall

180

1.72

3.02

- 2.71

Central air conditioner

77

3.69

4.24

0.43

Room air conditioner(s)

68

1.58

3.41

- 3.13

Heat pump

13

- 1.53

3.07

- 6.89

No cooling

22

- 0.21

0.00

- 1.55

Average lighting kWh savings per bulb

180

38.0

38.0

38.0

Actual per-bulb savings accounting for IE as a percentage of per-bulb lighting savings

180

104%

108%

93%

a Proportionally weighted to reflect statewide saturation percentage of ducted central air conditioning systems—see Section .

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