At what temperature is pellet stove vs head pump warranted

[slickcav]

Heat** pump warranted LOL

Trying to think this through in my head...

I guess what I have read some on here, is that I need to know when my "burning" season is, IE when to go full bore pellets with back up heat pump, vs no pellets all heat pump.

Electric heat pump costs X daily.

Pellet stove all day running burns 2 bags approximately in 24 hours @ 5$ even a bag @ 250$ a ton of Statesmen/50bags. 10$ a day, 300$ a month roughly if the pellet stove needs to run all day, each day, and there are no warm days in which I would shut it off.

I saw a calculator thread that talked about economics but it was from 2000 https://www.hearth.com/talk/threads/the-economics-of-a-pellet-stove-vs-electric-heat.38389/


So I do not have an electric bill of pure heat pump for a month, which maybe I should do? But here was my reading from my electric bill if you dont mind helping to interpret...

At what point in the Mid-Atlantic Region do you guys find the threshold where it is time to run your pellet stove vs no pellet stove and all heat pump? I live in a 1700 sq foot home with a walk out basement, walk out basement (unfinished side) has a Harman P38+, In the basement I have a vent on the return that will pull the warm air from the pellet stove and circulate through the house as I leave the fan on LOW instead of AUTO on the heat pump, I find optimal burn at feed setting 4, blower always stays max, those are my only controls. Burning Statesmen brand pellets. My house is 2002, well insulated, brand new HVAC systems and tankless propane Hotwater heater.

 

[slickcav]

 

[DBCOOPER]

Were you running the stove during this bill?

 

[SKOAL MAN]

The most pellets I have ever burned was 2 bags per day, give or take a couple pounds. It was -20 out out for 3 consecutive days. My home is a 1500 sqft elevated bungalow with a walkout basement R 12 in the basement R 20 upstairs R 32 attic. During those three days the house was 68 upstairs and 73 downstairs. I would love to have a ductless mini split system plus a pellet or wood stove but bank won't allow for mortgage on new build.

 

[Arti]

Lot's of variables, however as a general rule of thumb the heat pump will heat for less down to about 35 degrees F.
25 degrees and up the mini split will likely cost less than pellets.
Assuming that the heat pump is fairly modern and efficient.

 

[Deromax]

According to the manufacturer, my mini-split heat pump will work safely down to -4F, but there may not be enough actual heat produced in those conditions to keep up. In real useage, I found that below about 10F, the unit will defrost cycle regularly so I know it's time for the pellet stove to take over!

Calculating cost of operation is hard because we have no mean to know the actual efficiency of an heat pump at a given outside temperature. If the manufacturer would publish an efficiency chart, that would be easier to evaluate things!

 

[Snowy Rivers]

A heat pump with a good ground coil is good year round no matter what the outside temp

 

[Deromax]

But it's not the same upfront cost!

 

[SidecarFlip]

But it's not the same upfront cost!

+1 Thats Geothermal and raises the cost (install) substantially.

 

[hyfire]

I can make you a chart I just got my 32,000 btu heat pump today...I got all the specs and its not the most efficient model.

 

[hyfire]

Looks like your averaging approx 14 cents kwh.... My heat pump goes as follows:

80f outside temp= 11 btu/watt
32f " "=10btu/watt
0f=9 btu/watt

stove = 8400 btu x 40 lb=336,000 btu -20% stove eff=268800 btu

268800/3412 btu=78kwh

$5.00 /78,000 watts =.00641 cents per watt or 6.4 cents per kwh to run the stove equivalent.

to run the heat pump to give you 268,800 btu output at 0 F would cost you 268,800/9= 29,867 watts

Or 29.867 kwh x .13.8 cents a kwh = $4.13

At 32F it would cost you $3.72 to get the same as your stove!



But actually the stove cost more to run since it also uses hydro which is not factored in even yet. Which estimated at 200 watts =.33 cents hydro per bag, so now it cost you $5.33 per bag to run.

If its too cold the heat pump may not even give enough since the defrost cycle as mentioned...If its a ducted heat pump system with a furnace coil then it may not give you the output as a ductless split. We need the specs on your current heat pump system.


4.13/5.33= 22% cost savings over your pellet stove based on 0F outdoor temp

3.72/5.33= 30% cost savings over your pellet stove based on 32F outdoor temp

 

[hyfire]

According to the manufacturer, my mini-split heat pump will work safely down to -4F, but there may not be enough actual heat produced in those conditions to keep up. In real useage, I found that below about 10F, the unit will defrost cycle regularly so I know it's time for the pellet stove to take over!

Calculating cost of operation is hard because we have no mean to know the actual efficiency of an heat pump at a given outside temperature. If the manufacturer would publish an efficiency chart, that would be easier to evaluate things!

Senville would not give me that data either , I tried but they would not respond for some reason, so I moved on to a different manufacturer that would.

 

[hyfire]

Can you please change the topic..head pump sounds a bit strange...........

 

[DBCOOPER]

Here is my electric consumption compared to similar homes using heat pumps. I switch over at 32 degrees.

 

[DV]

I have never split hairs with calculations. I have a 3k square foot house. The year prior to installing my stove my electric heat bills were avg. 450 a month. And that's set at 66 and house cold. I installed the pellet stove and my avg bill is now 200 and my house is hot! I burn pellets from mid November to mid March so approx. 4 months of burning. Last year I burned 3.5 tons but this was on the high side because it was so cold. So if I burn 4 tons at approx. 250 per ton equals 1k bucks. Which is excactly what the difference in the 4 months electric bill is but....... the bonus is my house is actually warm. avg 70deg instead of 66. But to answer your question I usually don't burn pellets if it over 40 degrees.

 

[hyfire]

I have never split hairs with calculations. I have a 3k square foot house. The year prior to installing my stove my electric heat bills were avg. 450 a month. And that's set at 66 and house cold. I installed the pellet stove and my avg bill is now 200 and my house is hot! I burn pellets from mid November to mid March so approx. 4 months of burning. Last year I burned 3.5 tons but this was on the high side because it was so cold. So if I burn 4 tons at approx. 250 per ton equals 1k bucks. Which is excactly what the difference in the 4 months electric bill is but....... the bonus is my house is actually warm. avg 70deg instead of 66. But to answer your question I usually don't burn pellets if it over 40 degrees.

So your using electric heat if its 40F outside?

 

[DV]

So your using electric heat if its 40F outside?

Sometimes? It really depends on the daily high temp and if the sun is out. If sun is out and daily high is 45 I will shut stove down for the day. But if the high is 45 and cloudy will leave stove on. My house can heat up fairly well with sun beating on it.

 

[Wilbur Feral]

As others have noted, we find that for our air source heat pump (geothermal is not what most people think of when they say "heat pump"), it makes sense to switch over at about 32-35 degrees. Some newer and higher efficiency models will perform well a bit below freezing, and mini-splits likely do better than larger units as well, but there must be some reasonable amount of heat present for it to be "pumped".

We tend to turn on our family room stove at higher temps because the room it's in is much colder than the rest of the house, but that's a different story. However, it does bring up a point about losses from ductwork, etc. Many 1970's and earlier homes have inefficient ductwork that decreases efficiency of the central HVAC. For those owners, it may make sense to switch over at a point somewhere closer to 40.