Is it always cheaper to leave a heat pump on the same heat setting?


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Old 11-15-14, 03:59 AM
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Is it always cheaper to leave a heat pump on the same heat setting?

I'm curious of this as winter is approaching. My shop has a heat pump installed. It's a 25x25 shop with an 18' ceiling. The heat pump unit is sitting on the loft, up by the ceiling.

I normally keep it on 65 degrees which seems to be comfortable to work in but with the colder days coming(and now here mostly), I'm wondering what the cheapest way is to run this unit. The problem is that I usually don't work on the weekends, so all weekend I'm paying to heat the place to 65 degrees - seems wasteful. However, last weekend, I set it to 60 on Friday night and when I came in Monday morning, it ran for hours to get back to 65 so that seems like it was a bad gig.

Thoughts?
 
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Old 11-15-14, 04:46 AM
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You could disconnect the heat strips and just rely on the HP alone. It will take longer to raise the heat. I disconnected the heat strips on my HP mainly because my wife like likes to fiddle with the thermostat. I have a wood stove for when it gets too cold
 
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Old 11-15-14, 06:05 AM
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If the capacity of the heat pump is such that it ran "for hours to get it back to 65" I would say that it is sized fairly closely to the actual heating load.
Is it that the shop is fairly well insulated for the HP to not run that much when set to 65 but it's small capacity makes it take awhile to come up to temperature when you lower it for the weekend?

IMO the better your insulation the less savings you will achieve by lowering the temperature.
 
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Old 11-15-14, 08:20 AM
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Thanks for the responses!

When it ran for a long time that day, the aux heating wire was activated for a good time. I wonder how long this would have taken if I had that wire disconnected?

The shop is I-beam and corrugated steel construction but it does have very thick insulation on the inside walls. When it's very cold outside - 45 or below-, the pump does kick on fairly frequently but it holds 65 inside very well.

I had just wondered about this because it seems so wasteful to heat the shop for the weekend when I'm not there - but it might be even more wasteful to force the heat pump to run like mad on Monday morning.

My house has natural gas heat - it can warm the house very quickly, but I'm not really educated on heat pumps so I wanted to know if the old "set it and forget it" rule applies to my situation - that is, cheaper to just set it at 65 and don't touch it.
 
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Old 11-15-14, 09:10 AM
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Whenever the thermostat is raised more than a couple of degrees the heat strip kicks in which makes your elec meter spin The heat strip will also kick in when the temps get too low for the heat pump to keep up. I wonder if disconnecting the heat strips and using a programmable t-stat to kick in early monday morning would save you money ??
 
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Old 11-15-14, 09:18 AM
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Another thing to consider is that a heat pump is a mechanical device and usually slow and steady makes for a long and happy life.
I would suggest to just set the temp and leave it alone.
 
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Old 11-15-14, 05:10 PM
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Well, from a "cost to heat" perspective, if you're happy with leaving it at the target temperature 24/7 then so am I. I thought that was the most economical way to run a heat pump but I wanted a professional to agree with me on it. Thanks!
 
 

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