New HVAC system.

[mgbbob]

In April of 2021 we installed a 24K DIY heat pump in our 900 sq.ft. garage with 12’ sidewalls. We did all of the work ourselves expect making the electrical connection. After a bit of experimentation we decided to run the unit all the time with the thermostat set on 82. We would adjust if working but most of the time that was a good number. Reviewing past years it appears the unit cost about $3 per day on an average. Overall less than $100 per month through the hottest months. Less of course in spring and fall.





This cold snap has allowed us to take a look a winter weather. Heat pumps loose efficiency below 20 degrees so we were curious how it would do. We set the thermostat on 62, the lowest setting available and let it run. Sunday morning with 6 degrees outside the shop was 57 and this morning with similar temperature outside the shop was 56. Through the day yesterday it was in the 60s and very comfortable working with a long sleeve shirt on. The defrost cycle on the machine was working overtime! On Saturday I fired up the 5000 watt forced air electric furnace to see the impact. I ran it for an hour and it warmed right up to above 65 and the energy use for that day showed a 4KW bump so that cost me about $.60. Overall comparing past records it appears the heat will be in the $3 to $4 per day range. Reasonable to me to have a warm place to work.





So far we are very happy with the unit. I will continue to monitor how it performs. If we get some 15 below weather like last year I am sure I will need to supplement with the electric furnace but that expense will be for a short duration.

 

[fitter30]

24k btu's heat pump below 15*f only puts out 24kbtu's of heat garage must be well insulated. 5000 watt heater 16200 btu's.

 

[yeldogt]

In April of 2021 we installed a 24K DIY heat pump in our 900 sq.ft. garage with 12’ sidewalls. We did all of the work ourselves expect making the electrical connection. After a bit of experimentation we decided to run the unit all the time with the thermostat set on 82. We would adjust if working but most of the time that was a good number. Reviewing past years it appears the unit cost about $3 per day on an average. Overall less than $100 per month through the hottest months. Less of course in spring and fall.





This cold snap has allowed us to take a look a winter weather. Heat pumps loose efficiency below 20 degrees so we were curious how it would do. We set the thermostat on 62, the lowest setting available and let it run. Sunday morning with 6 degrees outside the shop was 57 and this morning with similar temperature outside the shop was 56. Through the day yesterday it was in the 60s and very comfortable working with a long sleeve shirt on. The defrost cycle on the machine was working overtime! On Saturday I fired up the 5000 watt forced air electric furnace to see the impact. I ran it for an hour and it warmed right up to above 65 and the energy use for that day showed a 4KW bump so that cost me about $.60. Overall comparing past records it appears the heat will be in the $3 to $4 per day range. Reasonable to me to have a warm place to work.





So far we are very happy with the unit. I will continue to monitor how it performs. If we get some 15 below weather like last year I am sure I will need to supplement with the electric furnace but that expense will be for a short duration.

Using supplemental heat is a reasonable way to go -- especially if it would have required an oversized system when looking at AC.

Many years ago I got good advise to not oversize my shop heater .. get the correct size and modulate the odd days with electric. It worked and that's my system. A space is more comfortable with a constant heat source and the proper heater for a space will not overheat. It may not have as fast a recovery or do all you want (like your heat pump) on the coldest day. I have found having a simple electric to flip on when you need faster warm ups .... or in your case when they heat pump falls behind is a great way to go. It ends up costing a few extra dollars --- that all.

Now with a heat pump you still need to size them correctly so you are not running the resistance all the time in cold weather. In my case my shops always had propane ... so when younger the cost was a greater concern. My heaters could always keep the spaces comfortable -- but like many I would turn it down if not there for couple weeks. Having that extra capacity was a big help if I wanted to use the shop when I got there.

Internet control has changes some of the need

 

[PoorUB]

24k btu's heat pump below 15*f only puts out 24kbtu's of heat garage must be well insulated. 5000 watt heater 16200 btu's.

Many of them will not do that well.

People don't realize all heat pumps are not the same. some stop heating at 0F some will run down to -30F.
I am guessing the OP's heat pump will not cut it below zero.

 

[Hobby_Man22]

What's the point in having the hvac running all day? Yeah it feels good, but it costs a lot of money especially if your system is big.

 

[Bert_]

What's the point in having the hvac running all day? Yeah it feels good, but it costs a lot of money especially if your system is big.

24,000btu x 24hr or 96,000btu x 6hrs

Which is more?

 

[Hobby_Man22]

Interesting. It's the same. Which you think will be worn out first?

 

[Bert_]

Interesting. It's the same. Which you think will be worn out first?

The one that starts and stops more.

 

[American Locomotive]

$3/day cooling seems pretty high to me with the shop thermostat set to 82 degrees! That's over 1kW continous 24/7!

 

[mgbbob]

I agree. The 5000 Watt heater was rated for 17,000 or good for about 500 sq. ft. Last winter at -15F it struggled but kept the temperature at 38F. It warmed up during the day. The roof is spray foamed and the end walls down to the 10' line are spray foamed. Most of the sidewalls are 3.5" batts with either particle board or sheet rock. I started with particle board but prices went crazy. A 15' section has only two layers of double bubble insulation. I forgot to mention that the entire building was wrapped with double bubble to start with. Two layers of double bubble does remarkably well and I really can't feel any difference between that and the other. The garage doors are 10' x 10' roll ups with one layer of double bubble. The below zero heat pumps were a lot more money so I rolled the dice. I am sure I will have to run the electric furnace if it dips below zero but the number of those days is pretty limited around here.

$3/day cooling seems pretty high to me with the shop thermostat set to 82 degrees! That's over 1kW continous 24/7!

24,000btu x 24hr or 96,000btu x 6hrs

Which is more?

The unit doesn't run at full capacity(24,000 BTUs) all day. It is a 20 amp circuit and if draws 15 amps (I really don't know) that would be 3.5 KW per hour or $.40 to $.50 per hour or $11 or $12 per day. Most of the day there is a small fan running and that is it. As far as leaving it on or off and $3 per day. 1. I can afford $3 per day, 2. I am retired and may work off an on through the day on different projects. 3. In the summertime the humidity is down all the time so I don't have to battle that when I try to cool the shop. 4. In the winter time I have chemicals, a refrigerator, and other things I don't want to freeze in the shop. It is really more of another room of our house. Everyone to their own. 5. The wife really likes the car 60 degrees in the winter when it is 10 outside. One of life's little luxuries! LOL

 

[mgbbob]

24k btu's heat pump below 15*f only puts out 24kbtu's of heat garage must be well insulated. 5000 watt heater 16200 btu's.

A recap of this morning. 10 degrees outside and the shop is at 59 degrees with the heat pump running. I am sure if it slipped lower overnight I would see the efficiency fall. So far so good.

 

[mgbbob]

The current weather has been a test for the heat pump. Snow on the ground for several days. The morning temperatures the last couple of days around 5F. This morning the garage temperature at the furthest point away from the air handlers was 52F. It is obviously struggling a bit and I haven't tried to identify the increase in KW hours yet but that is really immaterial since I know it is way less than the 5000 watt electric forced air I ran last year. So far I think the unit is a complete success.

 

[LS6 Tommy]

The one that starts and stops more.

You beat me to it.

Tommy