This calculator is used to determine incentives amounts from the California TECH HPWH Program when installing load shift capable central heat pump water heating (CHPWH) systems in multifamily buildings. The tool is designed to be easy to use and support appropriate design and controls for CHPWH installations. However, it does not negate the importance of manufacturer supported start up, commissioning, and ongoing maintenance.

Also make sure to check out the Ecosizer tool (link at top of page), which helps engineers determine the capacity and thermal storage required to meet the buildings load and achieve load shifting.

More Information
how to use this tool
  1. Before using the tool, you need to know what equipment you will be installing. If you need to size the system and select equipment, the best place to start is the Ecosizer sizing tool.
  2. Enter the project zip code. This information tells the simulation tool what weather file and CO2 emissions data to use.
  3. Provide number of apartments by bedroom type. This input is used to estimate annual load - both hot water usage and recirculation load.
  4. Select a primary water heating configuration type.
  5. Select a temperature maintenance system.
  6. Enter equipment information. Select CHPWH models from the drop down; enter storage volumes; enter electric resistance element information as required.
  7. Input load shift controls strategy. This includes the location of the temperature sensor and HPWH outlet temperature for each mode of operation. Grey fields are recommended setpoints and not user adjustable.
  8. Click “SIMULATE YOUR SYSTEM” and wait 5 to 10 seconds for results while the simulator runs baseline and load shift models and calculates emissions savings.
  9. Download a PDF of the results and send it to the TECH HPWH program portal to reserve your incentive.

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Peak Gallons per Day per Person calculated based on the expected 98th percentile of the specific combination of apartments sizes

Primary HPWH Configuration

Multi Pass

Not available in California
Specification Mode

Single-pass systems heat water to storage temperatures in one pass through the HPWH whereas multi-pass units heat water in several passes.

Temperature Maintenance System

Swing Tank

Not available with Multi Pass selected

Parallel Loop Tank

Not available with Multi Pass selected

Single Pass - Return to Primary

Not available with Multi Pass selected

Single Pass - No Recirculation

Not available with Multi Pass selected

Multi Pass - No Recirculation

Not available with Single Pass selected

Multi Pass - Return to Primary

Not available with Single Pass selected

A temperature maintenance system provides hot water to the taps in a timely manner.

Equipment Selection

Load Shift Controls

Single Pass

Multi Pass

Ecotope, Southern California Edison (“SCE”), Sacramento Municipal Utility District (“SMUD”), Bonneville Power Administration ("BPA"), Northwest Energy Efficiency Alliance ("NEEA"), and Oakridge National Laboratory ("ORNL") provide this software program (“Ecosizer”) for the intended “educational and informational” purposes only, and none of these funders guarantees that the information provided by the software is correct, complete, or current. While the computational results of the software may be used only for your design considerations, they should not be used for determining compliance with any applicable federal, state, or local laws or regulations. Please consult a professional to ensure accuracy for your particular requirements.

It is a condition of us allowing you free access to this Ecosizer software program that you agree to the following:

  • None of these funders, nor any of their employees, directors, owners, contractors or subcontractors, will be liable for any action you take in reliance on the information provided by the software. Additionally, you understand and agree that none of these funders makes any warranty, express or implied; or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any data, information, method, or results disclosed in this Ecosizer software program; or represents that its use will not infringe any privately-owned rights including, but not limited to patents, trademarks or copyrights.
  • Ecotope, SCE, SMUD, BPA, NEEA, and ORNL are providing this information in good faith for the intended “educational and informational” purposes only.

By using the Ecosizer software program and downloading results, you agree to the above conditions, and if you provide comments and suggestions for improvements to the software program they may be used for any purpose without restriction, obligation or remuneration of any kind.