US thermal networks are heating entire communities. Ontario should be next

National Observer

01-08-2025

Ontario is going through an energy transition that requires a creative approach to balancing affordability with the need to reduce greenhouse-gas emissions. To ease the upcoming energy crunch expected from industrial growth and new housing construction, infrastructure will need to expand over the next two decades. It won't be easy.
While most of the focus to date has been on natural gas and electricity, particularly nuclear power, overlooking thermal energy networks (TENs) would be a missed opportunity. These systems can cleanly and efficiently heat and cool buildings, using energy that's already around us — no fossil fuel imports required.
Thermal energy is in the soil and rock beneath our streets and buildings and in the wastewater that flows through our sewer lines. It is shed as heat from industrial facilities and data centres. It's abundant, local and emission-free.
The concept of tapping into thermal energy isn't new. For years, homeowners and building operators have used heat pumps to convert energy from the air or ground into space heating in the winter.
Now imagine if all the heat pumps across hundreds of buildings in a community were connected by a shared underground network of pipes, like a natural gas distribution network but instead filled with water. The heat pump in your home would pull the energy from the shared network, concentrate it, and deliver the warmth you need in the winter. In the summer, it would operate in reverse, taking heat out of your home and putting it back in the network.
This system, in essence, would act like a big battery bank, with hundreds of energy deposits and withdrawals happening across an entire community every day. Local businesses, industry, schools and community centres could connect to it, too. They'd need to pay a monthly fee to the utility that builds and operates it, but other than that it would be hassle-free, safe and reliable.
South of the border this model — often called "networked geothermal' — has gained traction, largely through the pioneering work of a Massachusetts-based organization called HEET. In 2017, it began conducting studies and working with regional utilities and legislators to promote the concept.
Thermal energy is in the soil and rock beneath our streets and buildings and in the wastewater that flows through our sewer lines. It's abundant, local and emission-free, write Tyler Hamilton and Audrey Schulman
It's arguably the most efficient way to electrify how we heat buildings. Every kilowatt of electricity used to power such a system is estimated to get the equivalent of more than five kilowatts back in the form of heating or cooling.
This, some studies show, is more than double the efficiency of air-source heat pumps that have been growing in popularity, meaning roughly twice as many buildings can be heated with the same amount of electricity. That leaves more electricity available for industry and electric vehicles and helps slow the need to expand costly electricity infrastructure.
Perhaps most compelling, these networks can use the same utility model already in place for natural gas services. This is why more than 26 gas utilities across the United States have joined a coalition co-founded by HEET to learn more. Even labour unions are embracing the opportunity. Taking the lead has been Eversource Energy, which provides gas, water and electric services in Massachusetts. It launched a first-of-its-kind pilot project in Framingham, Mass., moving 36 buildings and 135 customers off of natural gas service to a thermal energy network that became operational in 2024. If all goes as planned, the utility will apply what it has learning to other parts of its service territory.
We need to do this in Ontario.
To explore this opportunity, MaRS partnered with Black Swan Lab, previously known as HEETlabs, (a spin-off from HEET) and convened an 18-person working group of industry experts, who brought their expertise and diverse perspectives to the table, drawing from the energy utility, construction, housing, government and non-governmental organization communities. After six months, we released a roadmap report that includes recommendations on how Ontario can scale these networks province-wide.
The province seems open to the idea. It recently released a long-term energy plan where it asks the energy regulator and electricity system operator to study opportunities to 'enable responsible growth' of district thermal networks. We need more data and analysis of where these networks make sense for energy consumers and more experience building them to reduce economic and technical risk.
We also need municipal champions and provincial leadership. New York State and Massachusetts have passed legislation to restrict the expansion of natural gas infrastructure and enable TENs. That kind of leadership sends a powerful signal to the market.
Energy systems are complex. Nobody is suggesting TENs represent a silver bullet. It's also critical to recognize that natural gas will continue to play an important role, as it currently heats 75 per cent of Ontario homes. But GHG emissions in the province are rising, up about seven per cent since 2000. Natural gas is a big reason why.
If we're serious about reversing that trend, TENs must have a bigger seat at the planning table in Ontario.