Flexible-Voltage (120V/240V) Heat Pump Water Heaters Field Study

Advancing Gas Replacement and Equitable Electrification in the Pacific Northwest  

What Are Flexible-Voltage HPWHs? 

Flexible-voltage heat pump water heaters (HPWH) are a new generation of efficient water heaters designed to operate on either 120 V or 240 V power. Unlike traditional HPWHs that require a dedicated 240 V circuit, these units can initially be installed on a standard 120 V outlet, avoiding costly electrical upgrades. Later, if greater performance is needed, they can be converted to 240 V hardwired operation. This dual-voltage capability provides unmatched flexibility for retrofit and replacement applications. 

Why They Matter for Gas Replacements 

Most existing gas water heaters are not located near 240 V power, so traditional HPWH replacements require running new circuits and sometimes electrical panel upgrades — adding time and cost and can be a significant barrier in same-day, emergency replacements. 120 V plug-in HPWHs have already shown that they can dramatically reduce these barriers, enabling many homes to switch from gas to electric without major electrical work. Flexible voltage HPWHs go a step further by combining the simplicity of 120 V installs with an option to add the faster recovery of 240 V systems. Flexible voltage HPWHs also have innovative features such as integrated mixing valves and the ability to store water to higher temperatures, which are likely to improve performance and user satisfaction. 

 

This flexibility: 

  • Enables rapid gas to electric replacement at the point of failure. 

  • Reduces upfront cost and complexity, especially in older homes with limited electrical capacity. 

  • Expands deployment to underserved and low-income communities where panel upgrades are less feasible. 

AWHI Pacific Northwest Field Study

Objective

Building on emerging dual-voltage technology, the Advanced Water Heating Initiative (AWHI) is conducting the first field study in the Pacific Northwest to evaluate how flexible-voltage HPWHs perform in occupied homes — particularly in low-income households transitioning from gas water heaters. 

Partnerships & Implementation

  • Community Energy Project (CEP): Partnering to recruit and support low-income households. 

  • Great Northwest Installations: Serving as the certified installer. 

  • Pacific Northwest National Labs: Leading monitoring, data collection, and analysis. 

  • AWHI Research Team: Leading project management and funding  

Study Scope

  • 10 flexible-voltage HPWH units installed across diverse home types. 

  • Monitoring of energy use and performance over a full year. 

  • Tracking installation cost, contractor experience, and homeowner satisfaction. 

  • Documenting frequency and drivers of voltage upgrades (120 V to 240 V). 

  • Identifying how these systems perform as emergency replacements and in high-demand households.  

Key Research Questions

  1. Does flexible voltage HPWH technology maintain adequate hot water supply across typical and larger (4+ people) household usage?

  2. How often do installations start at 120 V and later convert to 240 V, and why?

  3. Does the flexibility enable faster, simpler emergency replacement of failing gas water heaters?

  4. What are the relative costs, benefits, and energy savings compared to conventional 120 V or 240 V HPWHs?

Expected Outcomes

This study will produce actionable insights including energy usage data, installation best practices, cost comparisons, and user satisfaction. These findings will directly inform the viability of this new type of heat pump water heater.  

Timeline

Installations are expected to occur in Q1 and Q2 of 2026 with the final report due by Q2 of 2027.