It's not at all obvious why you think this question is so obvious that it doesn't require a bit more context.

Why would it?

Manitoba has spectacularly cheap and plentiful hydroelectric power.

But is there enough surplus?

Yes. Manitoba already exports a lot of electricity to the Minnesota, Wisconsin, Saskatchewan, Ontario. It'll soon be bringing online the Keeyask dam as well which will add capacity for 400,000 more homes.

For today. But I presume when these reactors are completed, the question is will that surplus be enough for the energy needs of ~2030. And there the answer is "we need to build more generation". No?

Canada is a surprisingly unconnected federation of almost independent provinces. We don't have a great east-west interconnection between the provinces.

I mean, we have trade barriers between provinces. It's insane.

A big reason that Ontario can't / doesn't is that the demand centers in Southern Ontario are ridiculously far from the generation centers in Manitoba. Toronto is 1800 km straight from the new Keeyask Dam. This is over unpopulated muskeg that is expensive to build on in the first place and difficult to access for maintenance.

Yeah, Southern Ontario is for the time being not possible but perhaps Northern Ontario.

I imagine because it is cheaper to produce locally, or Manitoba does not have spare capacity. Why do you think they should import from Manitoba?

If it's cheaper to build these nuclear reactors as compared to "importing" hydro power from another Canadian province (these comments make it sound like it's another country) remains to be seen. Maybe it even looks that way from current estimates, but from past experience most estimates on the cost of building nuclear power plants are a bit optimistic...

This article suggests nuclear costs will go down as long as regulations are not changed mid-construction, or if grandfathering is allowed. https://constructionphysics.substack.com/p/why-are-nuclear-p...

Manitoba exports huge amounts of electricity to Ontario, SK, Minnesota, Wisconsin, and with the new Keeyask dam coming online it'll have capacity for 400,000 new homes. There's also still 1000s of MW of untapped potential in Manitoba, if investments would be made in dams and transmission.

The recent hydro project mentioned in the article is a lot more expensive than the Nuclear Options, although they may have cherry picked their data. It amounts to ~ 2x the cost. "BC Hydro’s 1,100 Mwe Site C dam is expected to cost $16 billion"

Probably to diversify and be somewhat self-sufficient.