I guess you'll have to believe me when I said I've done the calcs when I first sized my system. The website link is a convenient way to let other people play around with the numbers and see for themselves.
FYI The contractors were all trying to sell me a bigger system based on their gut feelings and experience selling bigger systems for more money. Fortunately I built my house and have a better grasp on the heat loads and heat calcs than they did. My two smaller units provide more than enough heating and cooling capacity.
I am a little pessimistic when it comes to contractors as they tend to err on the side of profitability vs providing what I need. If I'm wanting to buy a Prius as a single person commuter car I don't want to walk out the door with a 8 passenger 3/4 ton Suburban with a gas guzzling big block V8, HD tow and plow package.
I have no doubt you did your research
The only reason why I'm responding so in depth to your comment is I honestly believe your research could have been skewed without you realizing it (I have no clue why a multi zone would be double the cost vs two single zones on your end as my profit would be included in both quotes and I can't think of a time where it was double the price for a multi zone).
Good HVAC contractors will at least do a block load which takes minimal time. If you explain your thoughts to a good HVAC contractor about oversizing, they should do a complete load analysis of the home and explain in detail why they came up with a larger system (put yourself in the contractors shoes, take the time and do a complete load, and you run a 50/50 chance that the homeowner will shop that contractors load around looking for a better price when the other contractors don't actually have to do the work).
I don't generally deal with homeowners (I really don't want to LOL) but when I do, I try to live by the golden rule of doing unto others as you would have done to yourself (I think of the homeowner as like I'm dealing with my own parents). The reality is a business is in business to make money, but the question becomes what are you getting for the price being offered vs others? GOOD HVAC contractors need to make money, but they know the market well enough that they may have the nearest highest install price, but they shouldn't be off by thousands as long as your comparing apples to apples.
On that note, the few times I do sell, I won't lie. I'm generally the highest price (perhaps by about 10%). However, I sit down with the homeowner and compare apples to apples to what others are proposing and what I'm proposing (per scope of work and exactly what is covered). The key is spending the time and explaining what and why in what you're proposing. End of the day, it's all about trust. It's that trust that allows the homeowner to allow the contractor to compare apples to apples IMO.
I do however stand corrected per my last post. The only time I would talk about ROI is dealing with geothermal over anything else. The irony there is when you deal with the most efficient HVAC system on the market, you aren't comparing SEER ratings for ROI. Go figure
Not that it matters, but if I were selling to you, I'd do exactly what you did with two single zone systems over a multi 2 zone system, but not exactly for the same reasons
Tell me at least if someone sold you on Mitsubishi, someone at least offered you the MHK1 or newer MHK2 thermostat (should be a standard add on with ANY Mitsubishi system offered by a contractor IMO).
