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Energy Savings from Electric Water Heaters in Commercial Applications

Energy Savings from Electric Water Heaters in Commercial Applications. June 1, 2010. Ryan Firestone Navigant Consulting. Danielle Gidding Bonneville Power Administration. Purpose.

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Energy Savings from Electric Water Heaters in Commercial Applications

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  1. Energy Savings from Electric Water Heaters in Commercial Applications June 1, 2010 Ryan Firestone Navigant Consulting Danielle GiddingBonneville Power Administration

  2. Purpose • Propose energy savings for high efficiency electric water heaters in commercial applications, for both residential and commercial style water heaters. • Presentation Outline: • Efficiency metrics • Residential water heaters methodology and inputs • Commercial water heaters methodology and inputs • Measure savings and cost effectiveness

  3. NW Water Heater Presence in Commercial Buildings CBSA, all buildings 20,000 sq. ft. or less 43% (405M sq. ft) of small commercial building space has electric water heating Plus 9% (651M sq. ft.) of larger commercial buildings

  4. Water Heater Efficiency Metrics • Energy Factor (EF) • Used for residential standards • EF is the ratio of useful energy output from the water heater to the total amount of energy delivered to the water heater. • EF testing procedure: 64 gallons drawn in six equal amounts over 24 hours. • Standby Loss • Btu/hour or % per hour • Standby loss is the energy loss due to heat transfer from tank to ambient environment • Tank temperature = 135°F • Ambient air temperature = 67.5°F

  5. Energy Efficient Electric Water Heaters • Qin = Qrecovery + Qstandby • Where • Qinis the energy consumed by the water heater • Qrecovery is the energy consumed to raise the temperature of the supply water • Qstandbyis the energy consumed to maintain the temperature of the stored water • Qrecovery = Qout / RE • Where • Qoutis the thermal energy of the hot water used • RE is the recovery efficiency • RE is fairly constant across all electric water heaters (~98%) • Thus, Qrecovery is constant across water heaters for the same load. • For a given site, Qin (and therefore energy efficiency) is only a function of Qstandby

  6. Standby Loss as a Function of Energy Factor Assumes 4.4 kW power rating (average of all residential electric storage units in AHRI Directory) and 0.98 recovery efficiency

  7. Standby Loss as a Function of Energy Factor • Standby Loss (Btu/hour) = UxAx(Ttank – Tambient) • Where • U is the overall heat transfer coefficient (Btu/hour per ft2 per °F ) • A is the heat transfer surface area (ft2) • Ttank is the temperature of the stored hot water (°F) • Tambient is the temperature of the ambient air (°F) • UxAx(Ttank – Tambient) can be derived from EF, RE, and rated capacity (Pon)[1] • Heat loss is independent of tank size [1]Residential Water Heaters Technical Support Document for the January 17, 2001, Final RuleAPPENDIX D-2. WATER HEATER ANALYSIS MODEL (WHAM)http://www1.eere.energy.gov/buildings/appliance_standards/residential/waterheat_0300_r.html

  8. Residential and Commercial Water Heater Definitions • Residential [1] • 20 to 120 gallons • Up to 12 kW • 180°F or less • Typically 240V or 120V, single phase • Commercial • Anything not meeting all residential criteria [1] Federal Register, vol. 63, No. 90. Monday, May 11, 1998. 10 CFR Part 430 Energy Conservation Program for Consumer Products: Test Procedure for Water Heaters; Final Rule. Section I, 1.12.1. The Federal Register does not mention the voltage specifications, but manufacturers do market commercial water heaters meeting the first three criteria, but not the fourth.

  9. Current Federal Standards for Residential and Commercial Water Heaters

  10. Residential-type Water Heaters

  11. Current Federal Standards for Residential Water Heaters • Energy Factor (EF) • EF ≥ 0.97 – (0.00132 x Rated Storage Volume in gallons) • Effective January 20, 2004 • New standards will be effective April 16, 2015

  12. Residential Energy Savings Savings = StandbyLoss (EFbaseline) – StandbyLoss (EFactual)

  13. Residential In-store Product Distribution • Data from Summit Blue in-store cost research in OR and WA in 2008 • Each row shows the proportional representation of water heaters of the specified size range, by EF (relative to the Federal minimum), in the dataset

  14. AHRI/GAMA Directory of Certified Product Performance - Residential • Air Conditioning, Heating, and Refrigeration Institute (AHRI) • Formerly maintained by Gas Appliance Manufacturers Association (GAMA) • Residential Water Heaters: • certification status (approved/discontinued) • energy source (gas, electric, oil) • heater type (storage, instantaneous) • first hour rating (GPM) • storage volume (gallons) • rated power capacity (kW for electric models) • recovery efficiency (0.98 for all electric models) • Energy Star certified (yes, no) • 4258 models, 906 approved electric storage models

  15. Residential AHRI/GAMA Directory Distribution • Each row shows the proportional representation of water heaters of the specified size range, by EF (relative to the Federal minimum), in the directory Almost half of registered water heaters are rated at the federal minimum EF

  16. Residential Baseline and Measure Cases • Federal standard not an appropriate baseline given the number of products available above the standard • Sales and/or saturation data on EF not available • Use Summit Blue OR and WA in-store cost research (2008) as estimate of market • Data on 146 electric water heaters from big box retail stores • Supplement with data from AHRI/GAMA directory for less common sizes (30 gallon and 120 gallon) • Baseline - Use average EF based on Summit Blue and AHRI data by size • Measure – Select threshold such that the top ~25% of available units qualify as energy efficient • Average EF of measure qualifying units is the EF used for savings and incremental cost determination

  17. Residential Baseline and Measure Cases • Results from In-store and AHRI data Values in blue indicate a hypothetical case

  18. Residential Baseline and Measure Cases • Blended results: In-store, supplemented by AHRI

  19. Residential Costs • Data from recent (2008) Navigant Consulting/Summit Blue Consulting field research in WA and OR • OLS Regression: Cost = B0 + B1*∆EF + B2*Capacity • Capacity is the tank volume, in gallons • ∆ EF is the difference between the rated and the federal minimum EF • On average, a 0.01 increase in EF costs $24.60 • Incremental cost (per EF) not correlated to capacity

  20. Lifetime Assume 12 year lifetime

  21. Interaction Factors • CBSA – buildings 20,000 sq. ft. or smaller, with electric heating • Interaction Factors – 6th Plan for lighting • Conservative estimate because some water heaters are in unconditioned spaces

  22. Load Shapes • Electric – Flat 00-24h by 7d • Gas (interaction) – CommHEAT

  23. Residential Water Heater Cost Effectiveness

  24. Commercial-type Water Heaters

  25. Standby Loss (SL) SL ≤ 0.30 + 27/Vm (%/hr) Where Vm is the measured tank volume (gallons) Standby loss is expressed as the tank thermal energy lost per hour, relative to the ambient temperature. Standby loss typically specified by manufacturers as Btu/hour Current Federal Standards for Commercial Water Heaters

  26. Commercial Energy Savings Savings = StandbyLossbaseline - StandbyLossactual

  27. Commercial AHRI/GAMA Directory of Certified Product Performance • Air Conditioning, Heating, and Refrigeration Institute (AHRI) • Formerly maintained by Gas Appliance Manufacturers Association (GAMA) • Commercial Water Heaters: • certification status (approved/discontinued) • energy source (gas, electric, oil) • heater type (storage, instantaneous) • storage volume (gallons) • rated power capacity (kW for electric models) • Standby Loss (Btu/hr) • 1298 models, 81 approved electric storage models

  28. Commercial AHRI/GAMA Directory Distribution • Each row shows the proportional representation of water heaters of the specified size range, by Standby Loss (Btu/hr), relative to the federal maximum, in the directory

  29. Commercial Baseline and Measure Cases • Use AHRI/GAMA directory data (in-store data not available) • Baseline – use average standby loss (Btu/hour) in each size range • Measure – select thresholds (Btu/hour) such that ~25% of units in database qualify and use average standby loss of all qualifying units within each size range • Thresholds that obtain significant savings only include 15% of units

  30. Commercial Incremental Cost • Phone survey with plumbers and plumbing contractors • No awareness of commercial electric water heater efficiency • For baseline and measure descriptions and standby losses derived from AHRI, back calculate the equivalent EF. • Assume same incremental cost as a function of ∆EF as for residential type water heaters.

  31. Commercial Interaction, Lifetime, and Load Shapes • Use same values as for residential type water heaters • Lifetime: 12 years • Interaction: • -0.10 kWh per kWh of enduse savings • -0.0092 therms per kWh of enduse savings • Load Shapes: • Electric – Flat 00-24h by 7d • Gas (interaction) – CommHEAT

  32. Commercial Cost-Effectiveness

  33. Proposal • Approve savings for residential and commercial water heaters in commercial settings

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