Does Variable Flow Save Much Electricity in a Dry Climate?

[TangoFoxTrot]

In a dry, hot climate, do the variable flow setups really save much in the way of electricity? My understanding is where the savings kick in is when they can run at a low level and dehumidify a house and make it more comfortable.

If it's something like 110 and dry and it's running at full power to cool a home, is there much in the way of cost saving versus a traditional single speed?

 

[HoosierBuddy]

Tango...I don't know the answer to your question...but the thing I noticed on my setup was how much quieter it is (normally) as the fan is slow and the vents are puffing out air instead of blowing it out in a gale. The few times I've heard it spool up to 100% I've been very glad that it isn't that loud all the time.

It was an unexpected benefit of a 2 stage system with the DC variable speed blower.

Phil

 

[TangoFoxTrot]

Tango...I don't know the answer to your question...but the thing I noticed on my setup was how much quieter it is (normally) as the fan is slow and the vents are puffing out air instead of blowing it out in a gale. The few times I've heard it spool up to 100% I've been very glad that it isn't that loud all the time.

It was an unexpected benefit of a 2 stage system with the DC variable speed blower.

Phil

I'm not discounting that it's a nice benefit to not "hear" the AC when it's running and other creature comforts, just curious on whether some climates it might not be much in utility savings.

 

[ericm]

I don't think savings is the main point of the variable speed. Especially when it's running flat out. My understanding is that the point is comfort due to a more consistent temperature. That's what we noticed.

However newer systems are generally more efficient than older ones whether the new ones are variable speed or not. We did not notice a reduction in electricity costs after replacing our 28 year old system but we set the thermostat's cooling point a couple degrees lower now. We're more comfortable for the same cost.

It probably does not pay off in electricity cost savings alone. The added comfort is nice though hard to put a number on. And in any case our old blower died so we had to replace at least part of it anyhow.

 

[HoosierBuddy]

Tango....here's a calculator:

http://www.hvacopcost.com/

Just use the left side there and put in some numbers. Use your seer for both and on the standard leave it set on "A/C" and on the High efficiency choose "A/C Variable speed".

I just put in some garbage numbers and it kicked out $57 savings on cooling.

It's not going to be a lot. But the DC motor on these units uses a fraction of the energy. It's just that the fan motor isn't the big energy hog here...that's going to be the compressor motor...so potential savings is limited.

When I bought my equipment several years ago...I had a buddy in the trade get it for me at cost and he was worried that if I ever had to replace the motor it would be expensive...but that was like 10 years ago and I've had zero issues.

Phil

 

[yeldogt]

The multi speed systems are indeed very good at removing humidity .... but that's a byproduct of operation. It really the ability to match the load needed at the time where you see the benefits .... in energy savings --- but really comfort.

It always more comfortable when there is conditioned air being delivered -- be it hot or cold.

The more varied the temps .... the more you will fell the benefits. Yesterday it was 95 and sunny ... today it is overcast w/ rain and much less temp. The units in my house are matching the load --- no on and off.

Even most of the mid tier stuff today would be viewed as quiet .. the higher end stuff is silent. With my 3T carrier 5 speed -- I need to see the fan to know it's working.

In very cold weather .... say 5 degrees. I can hear it make some noise when it goes into defrost (it will make an occasional ... whoosh) .... and when it's running flat out. I can never hear it inside ...