You have an older system. New systems can provide 100% rated capacity well below freezing. Mine is -5F and not specifically a "cold climate" unit. The unit in OP seems to offer 100% nameplate capacity at 5F.
These are brand new heat pumps. I don’t think it’s possible to have high efficiency at cold temps because of the need for a defrost cycle. I just check and mine are around 2 COP at 8F and 5 COP at 40F.
It is not clear why your heat pump cuts over at 40 degrees if it still has COP of 2 at 8 degrees. Presumably a cost-effectiveness calculation if gas is cheap in your area. If you had heat strips instead of gas, the "cut over" temperature would be much lower. If your unit is capable of operating at full capacity below 8F, it would likely only use resistive heating below 5F. For most climate zones, that is fine and your unit does not sound like one specifically deemed a "cold climate" heat pump, the which now regularly achieve full rated output down to -15F. Of course, it's only rarely that cold even in "cold climate" zones so operating down at a COP of 1 for these short durations is not a real problem. The impetus for systems designed for lower temperature operation is not really aimed at those with cheap gas but at those living where heat pumps were previously only feasible for heating if using much more expensive ground source systems. Achieving year-round heat with only the heat pump eliminates the need for a furnace so you have to include this missing gear and installation cost in your analysis.
Sizing heat pumps by the sq. ft. is hairy reasoning. Load calculations take into account climate zone, insulation, building materials, orientation, ceiling height, etc. Any recommendation based on 2D area is sketchy. For replacement of existing professionally installed systems, going by the capacity of the installed unit is a better shortcut.
There is actually good reason to bump up capacity by half a ton to ton, unless currently installed unit was sized recently. The reason for this it's that design temperatures jumped up, sometime in a big way in a recent ashray published design conditions (and many companies don't even know that this is the case and use those from 10 years ago or more).
And even the published numbers tend to be off and they usually use one specific weather station in a region that may or may not have same weather as you.
When I replaced hvac a couple of years ago, I retained company to make manual j calcuation as none of hvac contractors were willing to do it. I provided it with design temperatures that I calculated after scrapping data from a bunch of private weather stations in few miles radius
Regulation has helped a lot! Government can act as the unifier of buyer's not that long ago central systems scored 6 now this lowballs at 18.
If you increase the time of operation you can earn greater return on the costs invested. Commercial water heating is storing heat cheaply now to avoid storing water warm that will be used as that causes biofilms and disease.
Healthy sleep in room you want to work in upon rising creates a challenge for live pumping of heat. A sudden heat is best and that means storing from day before. We thrive sleeping in cold being woken by warmth.
$20,000 on a four ton heating load is compromised by this design tragically.
"Cold climate" air source pumps have been available for years. Even my cheap MrCool Universal has 100% output down to -5F and it is not even really a "cold climate" heat pump.
Big resistive elements sitting in the air handler. Think big toaster oven coils that are used when the outdoor temperature drops too low for the heat pump to handle the load.
I recently purchased and installed a 3 ton MrCool Universal (Gree Flexx, I believe) with lineset for ~$4K shipped: https://hvacdirect.com/mrcool-universal-36-000-btu-heat-pump... Worked just fine during the Christmas arctic blast. We will see about longevity but at 1/3 of the price of your proposed units, I'm not worried about slapping a new one at any time. I am essentially on my own for service as no contractors will work on it but it seems your units would present the same problem.
My hats off to you for doing a DIY install. This is not a bad route to go if you enjoy/feel comfortable doing the work and don't care about air quality, smart thermostat integration, etc. Re contractors, we will have local contractor partners do the install and handle servicing, so you won't be left with an unserviceable system.
Are you able to say more about that? "We will have local contractors" sounds great but in my area I don't think you will be able to find anyone to work with you. The local contractors and supply houses have closed ranks to fend off internet sales. I can't even buy sheet metal from the local supply houses without presenting an HVAC license. These folks are seeing their livelihoods threatened by a looming shift toward the "appliance" model (which I for one surely welcome) so they would see partnering to service a model like this as slitting their own throats.
Agree 100% (I have my EPA cert and do my own installs)
Trying to bust into the HVAC company cartel will be the death of this idea. Most HVAC companies are highly local and have built their business around partnerships with supply houses and the US big-boy manufacturers (e.g. Carrier, Trane, Lennox). The Asian brands (Mitsubishi, Midea, Gree) have taken years to start penetrating the US market, and even then, many have done so through partnerships with the above US brands.
No reputable HVAC company is going to install a 'no name' dotcom branded unit that they won't be able to service with parts from their local supply house. They, and their suppliers, won't be getting the typical kickbacks or be able to mark up the unit costs and they likely won't offer any kind of warranty (at least on labor). To them, this is no different from Joe Homeowner ordering his MrCool/Goodman unit online and expecting them to install and service it for a low hourly fee. It's not worth their time or potential risk when the customer raises a stink a year later when that company reminds them they have zero warranty and parts aren't readily available.
There are ways of working with local HVAC contractors that provides value to them and doesn't just undercut their current way of business. Electric Air can provide lead gen, tools to support install, improved payment terms on jobs.
> This is not a bad route to go if you enjoy/feel comfortable doing the work and don't care about air quality, smart thermostat integration, etc
You're insinuating that doing the work yourself means you'll have poor air quality, poor thermostat integration etc. That's not true at all. If you've gone to the trouble to do a DIY install then you're now already experienced enough to install a heat-recovery ventilator to get fresh air into your home via an independent system. I installed my own ecobee thermostat with my heat pump and electric furnace and it works with HomeKit so is integrated with my entire ecosystem.
Reading their comment slightly overly charitably vs what was written (but almost surely in-line with what was intended), they were contrasting their unit that has a HEPA filter bundled as part of their unit and that is not part of the Mr Cool unit.
Exactly. There's lots of stuff you can stitch together yourself, and if you're a DIY person, its more fun/rewarding to do it that way. I think the majority of homeowners will want something that doesn't require doing the install themselves, or having to worry about overall system integration.
mr. cool has it's own smart thermostats/apps. you can use it also with nest/ecobee.
with regards to air quality, usually this kind of stuff better managed by dedicated systems.
