Conclusion

At least for heating the environmental benefits are pretty hard to argue with: the technology significantly decreases CO2 emissions. That by itself made the project feel entirely worthwhile.

On the down side, I was a bit disappointed that the business case for these technologies wasn't a little better. All the caveats about measurement aside, I do think the picture is pretty clear:

1. Replacing a natural gas furnace with an all-electric solution isn't a bad financial choice, but (at least with the 2023 technology I chose) you need to completely cut off your natural gas connection to come close to breaking even.
2. There are savings to be had with solar in Ontario, but they are pretty marginal given current energy and commodity prices.

Given where we were at even 10 years ago where heat pumps and solar were considered wildly infeasible and impractical for anything besides bespoke use cases without massive government subsidies, an economic argument of “slightly better than break even” is not so bad.