The impact would be as bad or even worse in Alberta, Saskatchewan, Manitoba and much of the Maritimes, regions with generating stations powered by fossil fuels - coal, oil and gas.
The giant Ontario Power Generation Corp., the province's main electrical utility, claims no one really knows how much Dion's tax scheme would drive up the average family's cost of keeping the lights on.
A spokesman says the utility would not comment on any political party's proposed policy, but "obviously someone would have to pay for increased costs."
One thing is certain: Under Dion's plan to impose a tax of $40 per tonne on greenhouse gas emissions, the increased costs to industry and ultimately consumers would be onerous.
For example, last year, Ontario's five generating stations that run on fossil fuels produced just over 28 million tonnes of greenhouse gas emissions.
As a result, Dion's scheme would slap a whopping tax of $1.1 billion just on those five power stations, increasing the cost of operating them by a staggering 80% or more.
As the spokesman for Ontario Power says, someone would have to pay.
In this case, that would be either Ontario consumers or provincial taxpayers who would be zapped for more than $1 billion a year, an increase of at least 20% in the operating costs of the utility, including its nuclear and hydro-electric facilities.
Environmentalists argue with some reason that the aging fossil-fuel generating stations are eco-monsters whose belching smokestacks should have been capped long ago.
In fact, Environment Canada lists the Nanticoke station on Lake Erie as the worst single source of greenhouse gas emissions anywhere in Canada.
The latest figures we have show Nanticoke alone belched over 16 million tonnes of emissions into the air in 2006, roughly the equivalent of half of all the regular cars in the country.
The problem is Nanticoke and the other four eco-offending facilities also generate about 30% of Ontario Power's total annual output of electricity, and throwing the switch on them anytime soon would leave much of the province in the dark.
Alberta would be even harder hit by the Dion tax plan with more than half of the promised $15 billion in annual revenues coming from that one oil-producing province.
Much of that would be from the oilsands - two Syncrude plants alone would have been smacked last year with over $1 billion in Dion's "green shift" taxes.
But like Ontario, ordinary Alberta families would be hit with soaring electrical bills to cover the environmental taxes on coal and oil-burning generating plants.
According to federal figures, seven electrical generation facilities in Alberta together produce almost 80% more greenhouse gas emissions than Ontario's worst five.
Were Dion's tax applied, Albertans would be stuck covering almost $1.8 billion on their monthly electricity bills.
By coincidence, the one province where electricity bills won't be touched by Dion's plan is the one with all that hydro power - Quebec.
Imagine that.