When soaring heat baked Ontario six years ago, the rising temperatures and high humidity sent power consumption to a record level and prompted public warnings to turn down the air conditioners and try to save electricity.

Fast forward six years to the recent hot spells in the province and no such warnings filled the airwaves. Power consumption didn't come anywhere close to that record usage of 27,005 megawatts on Aug. 1, 2006.

'We have more generation available in Ontario now to meet our needs but we've also seen demand come down.' —Alexandra Campbell

And, according to the folks who keep watch over the province's power grid, Ontario should have plenty of electricity throughout the summer to withstand any spikes in demand.

Rolling blackouts like those Alberta experienced earlier this week are not in the cards.

So what gives? How did Ontario go from fretting about keeping the lights on to the current power scenario?

There's no one reason, says Alexandra Campbell, spokeswoman for the Independent Electricity System Operator, the provincial government agency that oversees the power grid.

"It's a combination of things," she says. "A number of years ago, we were relying on importing power from our neighbours to meet our needs during the … extreme demand periods. We have more generation available in Ontario now to meet our needs but we've also seen demand come down."

That falling demand is a reflection of, among other things, the decline in the economy. Ontario's industrial and manufacturing sectors took a big hit with the international downturn in 2008, and less power is needed after companies scaled back or shut down operations.

"One of the biggest things that's changed is that some of the big industrial consumers have either left the province or have downscaled and are no longer using nearly as much power," says Warren Mabee, an energy policy expert and professor in the department of geography and school of policy studies at Queen's University in Kingston, Ont.

"And that just means that there is more power to go around."

Less steel and auto production

Mabee points in particular to reductions in steel production and auto manufacturing.

In the automotive sector, "we don't have as many shifts and I don't think we have as many plants in operation now with some shutdowns around Windsor, a shutdown in Oshawa and the associated parts manufacturing and things like that that go along with it."

Manufacturers have also upgraded and retooled plants with systems that don't require as much electricity.

"The industrial users get better with their power," says Mabee.

Overall in Ontario, peak demand for power consumption on extreme weather days has fallen by 2,500 to 3,000 megawatts, says Campbell.

So far this summer, Ontario's peak day was June 20, when 24,107 megawatts were consumed. The second-highest consumption came during the most recent heatwave: 23,900 megawatts on July 4.

"We could go as high as 25,000 — we wouldn't expect to go much higher than that," says Campbell.

While declining manufacturing has reduced demand since those peak days of 2006, other factors at play in Ontario's current situation include power conservation measures that residents have adopted as well as incentives offered to try to encourage people to use their dishwashers or washing machines at off-hours when the cost of electricity is lower.

Determining the relative impact on demand of each of those factors is difficult.

"It is pretty tricky to divvy up exactly how many megawatts are from the conservation or the demand shifting or the economy," says Campbell.

Still, she says there's evidence that people are taking advantage of the time-of-use rates, where they are available.

"A lot of what you're seeing is shifting to the weekends. So where people can do laundry and other things on the weekend, they're doing that, but there's also people waiting until 7 o'clock before they plug in their phone to recharge it or have their shower or that kind of thing."

Big load

Mabee says such shifting can be helpful for the overall power-generation footprint because "we do tend to get lots of nuclear power and excess wind power at night," and if it's not used, then "we end up … selling it at less than what we'd like."

"Nuclear is really the big culprit there because it is such a big load, 50 per cent of our power supply, and we can't shut [the reactors] off."

Mabee agrees there's no single trend to explain the current power situation; it is instead the result of a combination of reasons. He also points to changing living habits as a contributing factor to the decreased demand.

"From 2002 or 2004 until now, we've seen a big increase in the number of condominium dwellers, [and] not so much of an increase in terms of the number of single-family homes, which is going to bring power consumption down."

While demand has decreased, within Ontario there is also the ability to generate more power.

Ontario's electricity supply

Summer 2012:

Nuclear: 11,446 megawatts

Gas: 9,987 megawatts

Coal: 3,504 megawatts

Hydro: 7,947 megawatts

Wind: 1,511 megawatts

Other (wood waste, biogas, etc): 122 megawatts

Total: 34,517 megawatts

Summer 2006:

Nuclear: 11,397 megawatts

Coal:  6,434 megawatts

Oil /Gas: 5,103 megawatts 

Hydroelectric: 7,768 megawatts

Miscellaneous: 68 megawatts

Total: 30,770 megawatts

Source: The Independent Electricity System Operator

"Since we were in those tight periods … we've had some nuclear units refurbished and come online, and there has been a number of gas plants that have been built," says Campbell. Renewable sources such as wind power have also been added to the grid.

Campbell says the province expects to be able to meet its power needs in high-demand periods, although the weather can be notoriously unpredictable and have an unexpected impact on the power grid, as happened in the eastern U.S. recenty, when hundreds of thousands of people were left without power for days after severe storms swept through the region.

"If Mother Nature decides to start physically damaging equipment, then that's something that … is hard to protect against."

While Ontario appears poised to be able to handle whatever power demands are placed on its grid, Alberta ran into big problems earlier this week. Rolling blackouts hit Edmonton, Calgary, Red Deer and Lethbridge.

"I think that what's happened in Alberta is that they've had an awful lot of growth in a short period of time and that when you have that kind of growth pattern, it's difficult to ensure that your systems are going to be able to cover every eventuality," says Mabee. "They just got to the point they were pushed to the peak. It could easily happen in other jurisdictions."

Mabee says there's been a lot of planning for long-term power supply in Ontario that stands the province in good stead, even if something unexpected happens.

"There could be some kind of a seismic shift that would change … if suddenly a lot of heavy manufacturing flowed back into the province for some reason, that would change power demand and may drive calls for new nukes or for more gas-fired generation or things like that," says Mabee.

"But right now, based on demographics, based on what we know about our demand … and where we think we're going, it looks like we've got things well in hand."