PV-GEMS demonstration

PV-GEMS—Photovoltaic (PV)-powered, Grid Enhanced Mechanical Solution (GEMS)—is a whole building retrofit measure. PV-GEMS is an especially appealing retrofit option in cases where achieving significant energy savings through enclosure-based load reduction measures such as wall, window, and roof retrofits are considered not economical, too invasive, or otherwise problematic. 

Finding effective ways to retrofit existing and older buildings to be more energy efficient is critical considering there are 130 million buildings in the United States today and about 75% of them are expected to still be standing in 2050, according to the U.S. Department of Energy. Upgrading older homes is often expensive and intrusive, which makes homeowners less likely to make the investment.

How It Works

The PV-GEMS features a small, grid-independent photovoltaic (PV) system designed to partially power a high efficiency heat pump water heater, which replaces the home’s existing water heater, and a high efficiency minisplit heat pump, acting as an enhancement to a home’s existing central space conditioning system. PV-GEMS can also be configured to replace an entire central space conditioning system with heat pump technology. With PV-GEMS, no energy generated by the PV array is sent to the utility grid, minimizing grid instability, and pre-packaged deployment options minimize disruption to occupants and the home by delivering and installing a “pod” that is largely assembled off-site. 

The retrofit strategy provides a deep energy, whole building retrofit achieving 50-90% reduction in energy use intensity for heating, cooling, and water heating in single family detached and attached homes in all but very cold climates, when deployed along with cost effective, non-disruptive shallow retrofit measures including enclosure air sealing, duct sealing, and improved ceiling insulation.

In addition to energy savings, the PV-GEMS platform provides additional value through demand response capability, renewable electrification of space and water heating fuels, and resiliency through operation of critical loads when the grid is down.

PV-GEMS can work with most single-family attached and detached housing, however, the team is initially targeting older manufactured homes, which are often difficult to retrofit using traditional approaches.

There are more than 6.7 million manufactured homes nationwide and 45% of residents who live in manufactured homes are highly energy burdened.


The FSEC Energy Research Center (FSEC ERC) at the University of Central Florida, and its partners are working to retrofit eight manufactured homes and four single-family homes with the pod technology. A commercialization plan to manufacture and deploy the retrofit strategy at scale will be developed, as well as training materials for installers.

FSEC ERC will demonstrate the retrofit strategy in six states across different climate zones:

  • Colorado
  • Georgia
  • Massachusetts
  • North Carolina
  • Oregon
  • Texas.

The pod system holds promise because it is expected to reduce energy use by 50-75% and is less disruptive to install, according to researchers.


  • National Association of State Energy Officials (NASEO), a national non-profit association for the governor-designated energy officials
  • ROC USA,  a non-profit social venture scaling resident ownership, management, and improvement of manufactured home communities
  • Rheem, a global leader in the manufacture of high-quality, sustainable, and innovative water heaters, tankless water heaters, air conditioners, furnaces, pool heaters, and HVAC systems for residential and commercial applications

PV-GEMS is also engaged with:

Pilot Systems

In the initial testing of PV-GEMS in summer 2020, FSEC ERC conducted research on two different building types:

Large Capacity Pilot System

Small, one story commercial building painted in blue with yellow vents and red poles.
Building Science Lab
  • Designed for larger houses
  • Central space conditioning system replacement
  • 2.5 Kw Photovoltaic Array
  • 6 kWh of LiFePo4 battery storage

Smaller Capacity Pilot System

Manufactured Housing Lab
  • More economical solution
  • Applicable to most single family homes
  • Pilot lab is a 1,600 sq. ft., 3 bedroom, fully furnished manufactured house
  • 1.2 Kw Photovoltaic Array
  • 3 kWh of LiFePo4 battery storage


U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy

Research Period: 2021–Current