My opinion is that for a climate like Minnesota you should be looking at condensing furnaces. That climate has really cold / long drawn out winters. Efficiency in heating systems is where it's at for that climate. I think most condensing furnaces will be of the 2 stage variety.

You should shoot for efficiencies of 96% to 97% for your climate, you will only reach that in a condensing furnace. Where I live something like that would be over kill. Although newer builds here are often built with condensing furnaces.

Here where I live a 2 stage would be considered more as a comfort option, so you don't get blasted with high level heat all the time. 2 stage heat is a more gradual increase as 1st stage heat puts out less heat.

Outside of efficiency --- it's all about 'comfort'.

I service the Katy, Texas area.

The 2-stage is better in that it is more comfortable and will be quieter when operating in the low stage. There is some energy savings, but not enough to justify spending the extra money. There are 2-stage 80% efficiency furnaces available, but they given your climate I would not consider anything less than 95% efficiency.

In terms of reliability one could argue that the single stage may be more reliable since it is a less complex machine. But on the other hand a single stage could be cycling on more frequently which creates more wear and tear. If it fits the budget then go with the 2-stage furnace.

Is there an option to add a basement to this house? A basement in a very cold climate like Minnesota will be more comfortable and reduce the heating load of the house. Is the HVAC contractor doing a heating and cooling calculation?

Thanks everyone for the reply, this house does not have an option for a basement and the they only giving me the option to use Carrier in either 1 or 2 stage.

In terms of reliability one could argue that the single stage may be more reliable since it is a less complex machine.

They are both as reliable, assuming proper installation & proper maintenance. A 2 stage furnace uses a gas valve that has 2 stages of openness in 2nd stage it is wide open, in first stage is it partially closed.

The only 'real' difference from a single stage to 2 stage is almost always the gas valve itself and maybe the control board to the furnace. Outside of that, there isn't any difference until you step up to a condensing furnace--- condensing furnaces start at 90% efficiency and higher.

A gas valve whether it's two stage or single stage doesn't cause it to wear out any quicker. In most cases a furnace lasts around 20 years. Although you will probably start making repairs to it once the part warranty runs out.

Those repairs will come with either variety of furnace, not due to complexity -- but wear and tear from using it.

Wouldn't the variable speed motor be considered more "complex". While it should be reliable, I replaced a few Carrier ones in 8 years (on a 2 unit house). The pressures weren't too high in second stage and it ran 95% in first stage..

And then there is the cost when it does fail. Not truly a measure of reliability so i should have made that clear.

In my experience, a single stage motor got fixed for $300 and the ECM (of a Carrier 2 stage) was $1300. But you would have a far better handle on those costs.

Now - it certainly maybe that a basic "tract house" Carrier 2 stage doesn't use an ECM. And I think there are also 1 stages that use a variable speed motor. So the stage thing may not matter.

Mike - I totally agree. Maybe Minn has area where basements aren't done but a slab seems unusual from what I have heard. Slab can be plenty efficient but you are always better off putting some space underground from a HVAC run cost perspective. Hope the slab is well insulated.

David Cary, As of last year all newer furnaces come with an ECM motor at least currently. PSC motor *furnace* models have been discontinued.

So in terms of complexities around that of a blower motor, there isn't much difference in that check box any longer.

The motors you're describing are PSC motors. If I had to guess, these will slowing making their way to the junk yard. Maybe with in the course of 5 - 10 years this type of motor will likely be the minority. The HVAC market is constantly changing. It's slow, but it does change.

I wouldn't consider changing a blower motor complex PSC, ECM or Variable Speed, unless of course you put the furnace in first and then build the home around it, thinking you will never need to work on the furnace. Yeah, I've seen that too.

PSC motors tend to last much longer, but are the least efficient in operation. Not that you'll save anything in terms of replacement costs, by having the more efficient ECM or Variable Speed motor.

ECM motors can last a good while. Like anything else it's life is determined by a multitude of factors. I would say if you do everything right and with a little luck an ECM should last around 10 years or more, depending on system use. Things they are more susceptible to would be power surges and or operational heat.

The higher end variable speed motor is not much different in that regard.

David you bring up a good point. When homeowner on this forum asks which item is more reliable, they really want to know which will cost more to fix in the event it has to be repaired.

a two stage var speed would be better for a two story home...HVAC supply with adequate return though should be balanced between the two floors which can be problematic as far as good comfort...

A two story home would be better with two separate HVAC systems or *if possible* at least a 2 zone system for heating / cooling both levels appropriately.

A 2 story home with a single HVAC system will always be fighting itself with areas in the home too hot or too cold.

*heat rises / cool falls. The 2nd story of a 2 story home could be 10 degrees or more warmer than the lower level of the home.

This plays into the design of the comfort system. If you short change the design, that doesn't spell comfort when extreme weather comes.

In NC at least, you have to have separate floors be separately zoned. Of course we are more mixed than Minn. In my tight house, the upstairs unit is off all winter. And we have a closed bedroom door.

In the summer, the upstairs runs more than the down.

I wondered about modern furnaces and the variable speed motors. It is amazing how much electricity a blower motor can use.

So there probably isn't a reason to not do 2 stage other than initial cost. On the subject, how about 2 stage a/c? And is the OP also getting that?

" It is amazing how much electricity a blower motor can use. "

This depends on what kind of motor is in the furnace or air handler. The more efficient ECM units, which became required this past summer for all HVAC equipment, use substantionally less power than the type they replace. Something like 1/3 less power or more. The higher product lines of the various companies have had ECMs for a number of years but mid and lower tiers didn't always have them. Now all do.

Two ECMs in my main house running at the same time seem to together draw about 500-600 watts.

Austin can probably contribute the wattage he sees on motor labels for the equipment he sells.

Austin can probably contribute the wattage he sees on motor labels for the equipment he sells.

The advantage PSC motors have over ECM and Variable Speed is: long life. I've seen units upwards of 20 years old and older in which the original PSC motor still works. In most cases that PSC motor will probably last as long as 2 ECM motors. Maybe out live 3 ECM's in some cases.

The ECM motors, CIRCA 2020 cost much more than a PSC motor. So because you replace the ECM more often, and it costs more --- it is not likely to pay for itself in the way of reduced energy usage in most cases.

Worse case for variable speed I've seen is 3 years none other than Trane brand. Those motors -- you'll never recoup the cost via electric savings. Forget it.

So because I know it's not going to pay for itself, I don't pay that much attention to wattage... kind of out of sight out of mind.

One advantage ECM and Variable speed have over PSC is that they are quieter and do a better job in aiding the AC remove humidity. But with the recent Bosch Inverter AC, the jury is still out on that.

Maybe in 5 or 10 years--- more motor manufacturers make the ECM and prices come down things might change. But cost wise currently it's not going to save you enough to recoup the cost of the motor itself, in my opinion.

If you value a quiet furnace, then it would be worth it.

On the subject, how about 2 stage a/c?

For Minnesota this would be over kill. The cooling season is too short. It would be nice to have, but you'd only be doing it for better comfort.

Climate like Minnesota you'd never recoup the cost of a 2 stage AC. If you were considering heat pump for that climate like duel fuel gas and heat pump then it would make sense to go with Inverter Heat pump, like the Bosch as an example.

The Bosch has as many as 75 stages depending on the model chosen. So this would beat a 2 stage unit, like a dead horse. LOL.

As cold as it gets in this climate, I would want gas heat as a back up for sure though.

I agree - not worth it. But is the OP talking about a/c also? I have to imagine that in most climates, a 2 stage a/c doesn't pay for itself - mostly a comfort thing.

I am a bit confused on the ECM issue - is it required now or not?

I have Tranes in multiple locations. All single stage heat pumps. From 2009, 2011, 2019. I think I actually have 6 Trane 2 ton heatpumps - 3 houses, each with 2. Are these ECMs? Should I keep one around? - Probably not now since most are still under warranty.

My Carrier ECM drew 300 watts on low stage. I thought that was a lot but obviously that is perspective. My dad learned the hard way during a wildfire prevention induced power outage when his blower drew 600 watts and his inverter couldn't handle it. .

Here's a link I found for a Carrier page on the subject. I believe the ECM part is now required.

Carrier status report

The power draw of the blower is small compared to the power used by the condenser (compressor) when in A/C or heat pump use.

I am a bit confused on the ECM issue - is it required now or not?

yeah, this became effective this past July 2019. But the manufacturer's were allowed to sell remaining PSC motor furnaces left in stock. So it's possible if you bought a furnace this past year it could still be a PSC type blower. By now though I doubt you would find one if you wanted it.