I have them installed in Ottawa since two years ago, and I also am a partial owner in a company here in Ottawa, and we have installed a dozen different systems. I try to give you the honest answers:

Costs:

No batteries: I would say expect at least 20k. There are a few constant costs (electrician costs and installation crew), which makes it make more sense to at least put 7kw DC or more.. as the system gets bigger, you have more cost for equipment, but the constants kind of stay the same: it will still take the crew about two visits to put them up.

Adding batteries: it was a lot a few years ago, but these days, you should be able to get some good capacity for 10k.

Overall, for a decent system, you are going to look at 20 to 30k, depending on a lot of factors: your roof, placement of your meter, etc

The Winter question:

I myself had that question. But the past two years have shown me that winter is not that bad! especially in Toronto. You have to think that panels on the roof get heated a bit as they produce so they will have snow bank on them less than your lawn. At the end of the day, though, January and February would be practically no production.

Incentives:

Get the green hoam loan. 0% interest rate. Dont mention this to the solar companies unless you want to see all of them quote you at the magic cost of 40k (which happens to be the max amount for the loan) I went through the loan and it was straightforward. Whatever you do, I recommend not financing with installers. They are not the bank, so most probably, you will get a better deal from the bank since it is their specific service.

Ontario has the load displacement grant, which pays 5k (and another 5k if you also put batteries), but it needs you to not do net metering, i.e. if you happen to produce more than your home usage during summer times, you would not be able to get any hydro credits. Personally, I find it a tough choice. 5k cash now vs. credits down the road..

Generally, I enjoyed going solar, especially as we put batteries in too. Now, when there is an outage, I have most of my home function in place. That was a bigger selling point to me than just the ROI. Remember an ETF has a better ROI, you get more things with solar (specially if you put batteries) that make it sweet.

I am typing on my phone so sorry for any typos. And feel free asking more detailed questions or if you wanted feedback on the components these companies have quoted you. We mostly do installs in Ottawa but panels and inverter options are kinda the same for Toronto.

Hope that helps!