Isn’t it important to right-size non-heat-pump installs anyway? Too large a system causes short cycling, humidity problems, temperature swings. I have read installers habitually guesstimate over size to over charge (rather than do the proper calculations).
They oversize because customers who have an oversized system generally don’t complain but customers who have an undersized system definitely will complain when it can’t get to and hold their desired temperature.
The reality is that this is all solving a problem that people don’t have.
Forced air is a terrible way to heat a building yet thats how most homes are heated, and it is good enough for most people.
If you perfectly size a furnace for the coldest days of the year, it is now oversized for the other 90% of days.
The cheapest way is to install a multi stage heating/cooling system that works on first stage most of the time, and second when it needs to, like having 2 small furnaces. This passes the ‘good enough’ test for the vast majority of homeowners.
