Only eight of the 61 provincial power utilities will offer the new rate on the May 1 launch date. The rest have up to six months to get on board.
That means it will be available to 20 percent of the province's five million electricity customers, the Ministry of Energy confirmed to CBC News.
The Ford government's new overnight pricing was pitched as a money saver for Ontarians, undercutting its existing overnight rate from 7.4 to 2.4 cents per kilowatt hour. Both rates are set by the Ontario Energy Board (OEB).
"We wanted to roll it out to as many people as possible," Kitchener-Conestoga PC MPP Mike Harris Jr. told CBC News. "These companies were ready to go, and we're going to continue to work with our local providers to make sure that everybody can meet that Nov. 1 deadline."
Enova Power — which serves Kitchener, Waterloo, Woolwich, Wellesley and Wilmot — won't offer the reduced overnight rate until the fall.
Enova merger stalls adoption
The power company is the product of the recently merged Kitchener-Wilmot Hydro and Waterloo North Hydro.
The Sept. 1 merger is a major reason Enova Power isn't offering the ultra-low rate alongside the first wave of power companies, said Jeff Quint, innovation and communications manager.
"With mergers, a lot of work goes into them. We have to evaluate, merge and integrate several systems and processes," said Quint.
"We believe that we probably would have been able to make the May 1 timeline otherwise."
The ministry said retroactive pricing wouldn't be available, and Harris said he doesn't expect the province will issue any rebates to customers of companies that introduce the rates later than May 1.
"These organizations were able to look at rolling things out sooner. But, obviously — if you look at Toronto Hydro, London, Centre Wellington, Hearst, Renfrew — there's a dynamic range of large and smaller-scale providers there. I'm very hopeful the Region of Waterloo folks will be able to work to try and get this done as soon as we can," Harris said.