Heat pump water heaters
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Heat Pump Water Heaters. Provisional UES Proposal Regional Technical Forum October 4 th , 2011. Introduction. More time for discussion today than at the last meeting Decision today? We’ll see how it goes. What changed from last meeting 45 gal/day

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Heat pump water heaters

Heat Pump Water Heaters

Provisional UES Proposal

Regional Technical Forum

October 4th, 2011



  • More time for discussion today than at the last meeting

  • Decision today?

    • We’ll see how it goes.

  • What changed from last meeting

    • 45 gal/day

      • (was 40 gal/day for small tank and 60 gal/day for large tank)

    • Aggregated many measures (from 108 to 15 measures)

    • Tank size definitions

      • Small: 50 to 75 gallons

        • (was 55 gal or less)

      • Large: more than 75 gallons

        • (was greater than 55 gal)

    • Other more minor changes (we’ll point them out)

Measure summary

Measure Summary

  • Measure name: Heat Pump Water Heater

  • Measure description

    • Installation of a heat pump water heater instead of a standard electric tank water heater in single family site built homes.

  • Measure type: UES

  • Today’s Request: Discussion, Review, (Decision???)

  • Change in measure status: Proposed Provisional

  • Change in measure savings: n/a

  • Change in measure cost effectiveness: n/a

  • Other or follow-on work for RTF: Tier 2 interior

Ues analysis summary

UES Analysis Summary

Measure cost

Measure Cost

Measure life

Measure Life

  • 15 years

    • Same as standard RTF water heater measures.

    • Northern Climate Specification warranty requirements:

      • Tier 1: 6 years (Energy Star)

      • Tier 2: 10 years

Intermediate values measure aggregation methodology

Intermediate Values & Measure Aggregation Methodology



Heat pump water heaters

Note: These values do not take into account space heat interaction.

Heat pump water heaters

Eight Interior Tier 1 Measures

  • Annual Savings (kWh/yr)

One Unheated Buffer Space, Small Tank, Tier 1 Measure

One Unheated Buffer Space, Large Tank, Tier 1 Measure

One Unheated Buffer Space Tier 2 Measure

Four Interior Tier 2 Measures

Heat pump water heaters

  • B/C Ratio’s



Plans for additional ues s

Plans for Additional UES’s

  • Tier 2, Interior, with required Exhaust Duct

    • Plan to model within revised version of SEEM

      • New SEEM model (available this month) will perform a more detailed hourly simulation of whole house infiltration

        • This will include the ability to input exhaust fan schedules.

Study design

Study Design

From the Guidelines, for provisional UES status:

“A study design has been developed that is likely to result in data on efficient-case energy consumption that will support RTF approval for active UES values.”

Study design1

Study Design

  • Goal: Collect data useful in determining the next iteration of provisional UES for heat pump water heater measures.

    • Intentionally straying from Guidelines’ purpose of provisional data collection due to:

      • measure’s potential importance to the Region

      • expected evolution of HPWH technology over the next few years

  • Three primary data collection areas

    • Hot Water Consumption

    • Space Conditioning Interaction (model inputs)

    • In-field COP

  • Study Dates

    • Site/Participant recruitment

      • Program participants through 3/31/2013

      • Overlap of site selection across data collection areas expected

    • Study data collection period: 6/1/2013 – 5/31/2014

      • Installation of monitoring equipment would occur well before 6/1/2013

    • Provisional UES Sunset Date: 12/31/2014

Study area hot water consumption

Study Area: Hot Water Consumption

  • Data Collected

    • Monthly hot water consumption (gallons)

  • Sample

    • 200 sites

      • Random/representative sample of program participants

Study area space heat interaction

Study Area: Space Heat Interaction

  • Data Collected

    • Unheated Buffer Space-to-House UA

    • Unheated Buffer Space estimate of internal gains (equipment audit)

  • Sample

    • 50 sites

Study area in field cop

Study Area: In-Field COP

  • Data Collected

    • Hot water consumption (gallons)

    • Unheated Buffer Space-to-House UA

    • Unheated Buffer Space estimate of internal gains (equipment audit)

    • HPWH energy consumption

      • Compressor and Fan

      • Electric resistance

    • ΔT of water delivered

    • Ambient temperature

    • For tier 2 (assumes constant speed fan):

      • Two-time measurement of

        • airflow

        • incoming air temperature

  • Sample

    • 75 sites

      • Site selections weighted by program occurrence of HPWH model, installation location, and heating zone.



Open issues 1

Open Issues (1)

  • Baseline Energy Use Reliability

    • RCDP cycle 2 data too old? (from early 1990’s)

    • Is the 2.5 people/house assumption reliable?

    • Applying 45 gpd to both tank sizes

      • Will it “reliably” represent the future program participants?

Open issues 2

Open Issues (2)

  • Study Design

    • Adequate Study Areas?

    • Sample sizes?

      • Need input/statistics applied

      • Operating modes – will study design capture the “average” operating mode?

    • Length of study

    • Need a Control Group?

Open issues 3

Open Issues (3)

  • Analysis Approach

    • Gallons Per Day versus Household Size

      • Current proposal does not distinguish between household size.

    • Gallons Per Day versus ODT

      • Current proposal assumes the same volume of water every day of the year.

      • RCDP (kWh/month) and EPRI (gal/month) data show significant variation by month; DOE TSD shows significant variation by season.

      • Study Design allows future analysis to vary gal/day by outdoor temperature.

    • Space Heat Interaction

Open issues 4

Open Issues (4)

  • Sunset Date

    • 12/31/2014

      • Expected timing for study results and analysis completion

    • Also

      • New/revised equipment expected

      • New Federal Standard effective April 16, 2015

  • Measure Life

If there were to be a motion today it might look something like this

IF there were to be a motion today, it MIGHT look something like this:

“I _________ move that the RTF approvethe UES for Heat Pump Water Heaters under provisional status with a sunset date of December 31st, 2014.”

(Tier 2 interior location heat pump water heaters will be pursued/added at a later date.)

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