Setting back HP temp at night ?


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Old 04-08-18, 10:56 AM
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Setting back HP temp at night ?

Hello,

Running a HP with electric resistance aux backup. Operate under time of use Elctricty rates. More expensive rates during peak periods, in the winter, these occur between 7am-11am and 5pm-7pm.

Do folks set their Temps lower at night or try and keep temps constant? Iíve been running an experiment and itís tough to say which is better given the outdoor temp, radiant sunlight heat and other electrical appliance uses in the hous. Iím able to verify electricity usage by the hour through our utility providers website.
 
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Old 04-08-18, 11:35 AM
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It is always better to set the stat lower at night and during the day when you are not home. The rate of heat loss is less then if your heating system needed to keep the temp at a constant. For comfort, it is a good idea to have a programmable or smart thermostat so when you return home the temp will be at your comfort level.
 
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Old 04-08-18, 11:38 AM
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Unless you have a thermostat capable of locking out auxiliary heat, it’s best to leave the setpoint constant. The auxiliary heat will consume much more energy then then the heat pump would maintaining a constant temperature.
A lockout style thermostat prevents this issue by not allowing use of auxiliary heat above a certain outdoor air temperature.
 
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Old 04-08-18, 12:02 PM
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Looks like one vote for each option. Let the debate begin.

Setting back is obviously s good choice for gas or propane, but donít think the debate is so clear when using a HP.

Let the poll continue.....
 
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Old 04-08-18, 12:17 PM
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As roughneck said...unless you can lockout aux heat...setting it back could cause the strips to come on during the normal return to higher set point operation. That will likely eliminate any savings you may gain by setting back in the first place.
 
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Old 04-08-18, 12:17 PM
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I have GEO thermal HVAC which is a glorified heat pump. The problem with these systems is they do not have a big heat gain like a gas furnace.

At first we started setting ours back several degrees but found that it would then take hours of run time on the cold days just to get back to the higher set temps.

Now we just leave it at single temp and enjoy the savings!
 
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Old 04-08-18, 01:13 PM
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I do not live in the land of heat pumps so you should take that into account of my post.
 
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Old 04-08-18, 05:05 PM
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This really isn't a debatable issue. The electric reheats will eat up any setback savings. That is a fact. Yes.... you can change when the aux heat is active but if you don't have it come on.... it could take hours for the heat pump to gain the few degrees back.

Gas is a completely different issue.
 
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Old 04-09-18, 02:45 AM
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Here is my 2 cents; any time you need the "electric back-up heating coils" to correct the temperature in the house, any savings from a heat reduction will be compromised. The cost to run the back-up heat coils is much greater than the cost to run the heat-pump alone. What the difference in cost is, is determined by your geographical location, the overall design of your home, your cost for electricity and the age of your equipment. Newer heat pumps can be more efficient than older units due to design enhancements. Because of these variables guys that monitor this site can only guess on the cost savings for different scenarios of temperature set back and day-time set points. Myself, for the last 40+ years I have lived in houses with an oil furnace, heat-pump with oil back-up and natural gas. My winter temperature was a constant 72 degrees with no night time set back . I prefer comfort and do not want to get up at night for a bathroom call and freeze until I get back into bed. (JUST MY CHOICE)
 
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Old 04-09-18, 07:15 AM
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Newer heat pumps are more efficient, however electric heat is still electric heat. It has been and always will be 100% efficient.
 
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Old 04-09-18, 09:07 AM
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There is a big cost difference between BTU's from heat pumps and electric heating elements.

Electric heating elements provide 3412 btu per kilowatt. Heat pumps powered by electric motors typically provide three or more times that ....10,000 + btu

One of the spec's for heat pumps is COP or Coefficient Of Performance the ratio of heat output to the amount of energy (electric) input for a heat pump.

Electric heating elements have COP of 1.0 Heat pump COP varies with outside temperature. My Chinese splits have COP of 3.1 to 4.+ so cost per btu is about 1/3 of electric.
 

Last edited by doughess; 04-09-18 at 10:21 AM.
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Old 04-09-18, 07:20 PM
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Running a HP with electric resistance aux backup. Operate under time of use Elctricty rates. More expensive rates during peak periods, in the winter, these occur between 7am-11am and 5pm-7pm.

Do folks set their Temps lower at night or try and keep temps constant? I’ve been running an experiment and it’s tough to say which is better given the outdoor temp, radiant sunlight heat and other electrical appliance uses in the hous. I’m able to verify electricity usage by the hour through our utility providers website.
Are you by any chance in ontario, canada?

Super expensive electricity and the best way to save is to keep the heatpump for a/c only and install a gas furnace for heat if you have gas available.

The others are right, programmable thermostat and heatpumps don't mix; while some better thermostats can use an outdoor sensor to lock out the backup and also try to keep the aux heat off when recovering, the capacity to reheat just isn't there much of the winter in most cold climates.

One thing you can do is install a second programmable thermostat and wire the aux heat wire through it, then program it to keep the expensive aux heat off from 7am to 7pm or a variation of that with multiple periods.

Can have the aux heat set back from 7am, bring it on from 3 to 5pm to warm the house up if heatpump can't do it alone (presumably mid peak) and set back again from 5 to 7pm.
 
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Old 04-10-18, 09:12 AM
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Thanks. Yes in Ontario. No access to natural gas. Propane only. And from my calculations and research, it seems that electricity at 0.12 kwhr (what I average) is pretty close to propane at 0.70 cents litre.
 
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Old 04-10-18, 09:46 AM
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Keep the heatpump running, if you want find a way to keep the aux heat off.

0.12 kwhr (what I average)
After distribution cost per kwh it's more.

it will go up in the future once the "fair hydro plan" bs ends.
 
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Old 04-10-18, 03:19 PM
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0.12 kwhr is all in. Weíre pretty good at managing our time of use. Approx 75% is used at the lowest rate. I think fair hydro or something similar is here to stay. I paid over $600 in January alone for hydro. WiThout it, me and my neighbours would be well over $800. the local nat gas company doesnít want to bring service to my neighbourhood.
 
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Old 04-10-18, 07:09 PM
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The fair hydro plan - what they're doing is borrowing money against opg to temporarily lower the bills. It's going to come back and bite us in the ass in interest costs and the real cost of electricity will keep on going up by like 10% per year thanks to bad contracts and policies. Not only will the cost be higher, but in the future interest/servicing the debt will be rolled into the rate.

So hydro here is going to become way more expensive than it already is.

Best you can do is try and keep the aux heat off during mid and peak periods and make the house as energy efficient as possible when it comes to heat loss.

There are heatpumps out now that do a far better job of maintaining capacity as it gets colder without aux heat, but they're probably very pricey and wouldn't make sense to replace an existing unit that's still working.

The aux heat is the killer.
 
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Old 12-22-19, 07:23 AM
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If the outdoor temperature is at or below freezing, might it make sense to setback a heat pump?

You know for sure, the aux backup is gonna run all night to maintain the heat since the outdoor temp is so low. Wondering if it makes sense to set it back and have the temp (and aux heat) come on in the morning.

Traditional thinking says to not set back since the heat pump may be able to provide enough heat throughout the night without the aux. but if you know the aux is coming on throughout the night, it might make sense to setback.
 
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Old 12-22-19, 08:08 AM
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The heat pump will still produce heat at freezing. Let it run over night.
 
 

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