Rooftop solar has the potential to transform Canada’s energy landscape by cutting costs and emissions, but it needs better homeowner incentives and effective grid planning to prevent the surplus energy issues recently faced by utilities in Australia.
Right now, just one in 200 Canadian households is equipped with rooftop solar panels, reports CBC News. Analysts at Dunsky Energy + Climate say [pdf] current policies can bring that to one in 12 homes by 2050, and with more financial support, one in nine homes is possible. With an even bigger push—expanded policy support, financial support, permitting and grid interconnection enhancements, and mandates for solar in new homes—one in three homes would have solar arrays. That’s the 20- to 40-fold increase that Canada needs to get to net-zero by 2050, the Dunsky team says.
Rooftop is Greener
With much lower levels of embedded carbon, rooftop solar systems generate 18 to 59% fewer carbon emissions than their utility-scale peers, found a recent study from Western University. While utility-scale solar needs platforms of carbon-intensive concrete or steel, rooftop solar uses pre-existing infrastructure, explained study lead Joshua Pearce, an engineering professor at the university.
“You just have fewer materials involved.”
The Ontario Clean Air Alliance found [pdf] that many single-family home rooftops can accommodate a 10-kilowatt solar array or more—generating enough electricity for the household while avoiding 1.5 tonnes of carbon emissions per year. “That will increase to 3.9 tonnes per year by 2030 by displacing electricity from Ontario’s increasingly gas-reliant electricity grid.”
A ‘Massive’ Hedge Against Inflation
But rooftop solar comes with high up-front costs, writes CBC News. An average 7.5-kilowatt solar array would cover a family’s electricity needs, but at a cost of around C$22,500 in British Columbia and $25,000 in Ontario.
The payback period on that investment varies, but averages 10 years in provinces with fossil-heavy power mixes, like Alberta and Saskatchewan. The OCAA report placed the payback in Ontario at up to 27 years.
Western’s Pearce said homeowners running the numbers on rooftop solar should factor in inflation. “When you do that, you see that solar is actually a massive inflation hedge and all of your ‘income’ coming from it is not taxed because it’s savings.”
Utilities can also compensate customers with rooftop solar for the power they generate, but they have little scope to do that in Canada. Most provinces “limit the power generation of a rooftop solar system to the amount you consume, and customers can only be compensated in bill credits, not cash,” CBC writes. Those credits often have a very limited shelf life of less than two years. The approach penalizes rather than encourages rooftop solar, even though households are helping utilities control costs and cut emissions.
Complications from Curtailment
In contrast, a sunny winter Saturday in Australia found rooftop solar accounting for 46.5% of the main grid’s supply, which led to a dramatic drop in electricity prices, reports RenewEconomy. Prices across the grid averaged between minus AU$30 and minus $68 per megawatt-hour between 8 A.M. and 4 P.M. that day.
To avoid financial losses, wind and solar utilities curtailed output, highlighting a key issue: when too much solar power is produced, it can lead to excess supply and the need to limit generation.
Canada has faced similar curtailment issues, such as in 2019 when Ontario took 6.5 terawatt-hours of clean electricity offline, reports McMaster University’s The Powerline. The billion-dollar loss of electricity could have powered more than 650,000 average homes over an entire year.
Addressing these challenges will require more energy storage, plus other technologies and policies to shift demand or create demand through mechanisms like sector-coupling (i.e. power-to-heat, power-to-transport), Renew Economy writes.
California-based GridX has more on curtailment here.
