Garage shop air conditioning

[longview]

About 2 years ago I insulated most of my detached garage, and added a 1 ton ductless minisplit heat pump, that I installed myself.
Since I have been completing the insulation, to the point the AC unit can keep the space comfortable even on the hottest days.
This next week in my area is going to be about the hottest of the year, with temps near 100 F and no rain.
My minisplit just has a 110v plug, So I plugged it into a power meter, at 8:00 PM last night, and will let it run until 8:00 pm tonight,
to record the 24 hour consumption, (I was up to 8 kWh at 6:00AM this morning.)
The garage started very hot, so there may be some extra consumption just cooling the garage down.
I am trying to get a feel of what it will cost to run the minisplit full time, at 73F, 74 F, 75F, as I will be spending a lot of time
in the garage when I retire, (soon).
Any thoughts on if the 24 hour test is good, or should I check the second 24 hours with the garage starting cool?

 

[Chock Full o Nuts]

Of course it's going to work overtime for a few to get down to desired temp. I'd say monitor it at least a couple days or so as you deal with cooler temps at night and daytime heating to give a good average.

 

[humbolt]

You could use heating and cooling degree day calculations to get a somewhat accurate picture of consumption once you have a baseline for your HVAC equipment. If you’re looking to establish a budget, that would be close enough.

 

[iliveonramen]

I think a 24 hour tests sounds good. One thing I wouldn't do is test in extreme temps. You're trying to control for as many variables as possible, when temps get above 95%, you can see a large loss of efficiency for AC's and that will create a lot more variability that will mess up your results. 95 degrees compared to 96 degrees is going to show a bigger difference than 92 and 93.

If the goal is to budget and find a temp you can keep it for during the summer that wont break the bank, I'd choose a different outside test temp than 100 degrees. I don't know about Texas though, maybe you guys get a lot more 100 degree days than we get here in Florida.

 

[longview]

I think a 24 hour tests sounds good. One thing I wouldn't do is test in extreme temps. You're trying to control for as many variables as possible, when temps get above 95%, you can see a large loss of efficiency for AC's and that will create a lot more variability that will mess up your results. 95 degrees compared to 96 degrees is going to show a bigger difference than 92 and 93.

If the goal is to budget and find a temp you can keep it for during the summer that wont break the bank, I'd choose a different outside test temp than 100 degrees. I don't know about Texas though, maybe you guys get a lot more 100 degree days than we get here in Florida.

A follow on experiment will involve serving this load with solar panels and batteries, so I want to know what the peak is also.
I ran it last summer during a big heat wave, and it was able to keep the temps in the high 70's, but have completed a lot of insulation since then.

 

[Rexedgar]

I have two outbuildings with mini-split systems. Both are masonry, one 900 sq’ and the other 1500 sq’. They both retain the night cooler air and do not take very long to make the shop area comfortable. Both building have ceiling fans to move the air around. I rarely run them for 24hrs. One is a heat/AC unit one just a/c.

 

[longview]

I have two outbuildings with mini-split systems. Both are masonry, one 900 sq’ and the other 1500 sq’. They both retain the night cooler air and do not take very long to make the shop area comfortable. Both building have ceiling fans to move the air around. I rarely run them for 24hrs. One is a heat/AC unit one just a/c.

Yea I do not think I will run it 24/7 ether, this is more of a test.

 

[longview]

Yea I do not think I will run it 24/7 ether, this is more of a test.

Quick follow up, From 8pm on 7/21 to 8pm 7/22, I recorded 23.4 kWh of use.
and the garage held at 73F, a little cold.

 

[Checkerboard Strangler]

About 2 years ago I insulated most of my detached garage, and added a 1 ton ductless minisplit heat pump, that I installed myself.
Since I have been completing the insulation, to the point the AC unit can keep the space comfortable even on the hottest days.
This next week in my area is going to be about the hottest of the year, with temps near 100 F and no rain.
My minisplit just has a 110v plug, So I plugged it into a power meter, at 8:00 PM last night, and will let it run until 8:00 pm tonight,
to record the 24 hour consumption, (I was up to 8 kWh at 6:00AM this morning.)
The garage started very hot, so there may be some extra consumption just cooling the garage down.
I am trying to get a feel of what it will cost to run the minisplit full time, at 73F, 74 F, 75F, as I will be spending a lot of time
in the garage when I retire, (soon).
Any thoughts on if the 24 hour test is good, or should I check the second 24 hours with the garage starting cool?

We didn't install an AC unit, but we DID install a hybrid heat pump electric water heater.
The output of the heat pump is cold air, so without even trying, we have the equivalent of an air con in the garage.
Yesterday it was in the upper 90's and our garage was about 80.
Close enough!

 

[longview]

We didn't install an AC unit, but we DID install a hybrid heat pump electric water heater.
The output of the heat pump is cold air, so without even trying, we have the equivalent of an air con in the garage.
Yesterday it was in the upper 90's and our garage was about 80.
Close enough!

Technically the mini split is a heat pump, as it both heats and cools.
I tried the heating function last year, and it works, but not as good as the AC.

 

[Checkerboard Strangler]

Technically the mini split is a heat pump, as it both heats and cools.
I tried the heating function last year, and it works, but not as good as the AC.

This is the former heat pump water heater we took out.
The fan is where the cold air comes out.
The new one is similar, just larger, same idea.
Heat pump water heaters use about 1/3 the amount of power compared to conventional electric water heaters.