# Pellet stove vs Heat Pump



## freeburn (Oct 22, 2008)

Question for all you heating and cooling experts. Tell me what you think and back it up with stats preferably. 

I have a new heat pump that is rated 14 seer/8.5 hspf?  I was wondering if it is more economical to run it during the 35-40 degree weather or the pellet stove? House is well insulated, and live in Wisconsin. I don't have any months to compare cost. 

I eagerly await your reply. Thanks.


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## BubbRubb (Oct 22, 2008)

What is the size of the area you are heating and what is your electric cost / kwH?


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## DiggerJim (Oct 22, 2008)

jburner said:
			
		

> Question for all you heating and cooling experts. Tell me what you think and back it up with stats preferably.
> 
> I have a new heat pump that is rated 14 seer/8.5 hspf?  I was wondering if it is more economical to run it during the 35-40 degree weather or the pellet stove? House is well insulated, and live in Wisconsin. I don't have any months to compare cost.
> 
> I eagerly await your reply. Thanks.


The balance point of your heat pump is right in that 35-40 degree range. That's the point where it will run constantly to keep the house warm. Below that temp is where the resistance coils kick in to supplement the heat it's able to extract from the air. The resistance coils are the most expensive way to heat electrically speaking and will cause your meter to spin really really really fast  Unless you've got really cheap electric (mine is 18.5 cents/kwh) and really expensive pellets, anything under 50 degrees outside temp is starting to be more expensive to use the heat pump - and below 40, definitely. OTOH, you have to offset the heat pump electric use with the electric you'll use with the pellet stove - you can find that consumption (usually a few hundred watts/hr) in your stove's manual. You also have to factor in the use of your heat pump as a whole house central heater (which means all rooms are warm) vs. the pellet stove as a space heater (where only some rooms are warm) in your decision making.


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## sbatzold (Oct 22, 2008)

I've found in the past 5 years it was more efficient to run my Heat Pump over my pellet stove here in upstate NY, than again I have a Geothermal Heat Pump:0)


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## freeburn (Oct 22, 2008)

Sq footage is approx. 2000 up and down. Price is 9.16 cents/Kwh That's the winter rate anyway. Oh, and my Heat pump is air source, perhaps that a given.


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## webbie (Oct 22, 2008)

I would say that the heat pump would be cheaper and more efficient at that temp.

Most heat pumps have a COP rating at various temps.....a very good one would have a COP of 3.0 at those temps.

That would mean we get 3x as much heat out of the electric than resistance heat.....so let's put a cost per KWH of 3.1 cents for the equiv heat.

That would be:
$8.79 per Million BTU of Heat delivered to home 
Let's add some fudge for a less efficient heat pump, etc. and say $11 per million BTU

Pellets - at $225 a ton - delivered to your house and put into the stove:
$19.93 per Million BTU of Heat delivered to home 
at 70% total AFUE efficiency

It would appear that in almost any case, a modern heat pump with high COP in 35-40 degree weather would beat pellets when electric costs were relatively low. Some of this is regional, since we pay .17 cents or so where I live - then again, pellets are currently $300.

But in your case, the Heat pump seems to be almost 1/2 the price.


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## jdlitwiller (Oct 22, 2008)

I stumbled on this forum with this very question in mind. Is a $1200 dollar stove and $250/ton pellets worth the investment (over x amount of time) versus keeping a 1700 square foot house warm with $.13 kilowatts?


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## freeburn (Oct 23, 2008)

I also got my pellets for $154/ton. Had the pellet stove already and didn't pay $1200. It was in place of putting in a fireplace. I call it a useful fireplace.


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## webbie (Oct 23, 2008)

jdlitwiller said:
			
		

> I stumbled on this forum with this very question in mind. Is a $1200 dollar stove and $250/ton pellets worth the investment (over x amount of time) versus keeping a 1700 square foot house warm with $.13 kilowatts?



I really doubt it - in terms of $$ alone. In fact, when hassle, service, parts, etc. are figured in, pellets would probably cost more.....over time.

Most purchasers of wood or pellet stoves have multiple reasons - enjoyment, recreation, backup, renewable, etc.


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## BubbRubb (Oct 23, 2008)

I have a heat pump w/ electric resistance backup.  However, electric is anything but a warming heat.  The heat pump is used until around the end of November and then the pellet stove goes on.  As Craig said, we all have different reasons.  With the stove, my wife isn't nagging me about how she is cold or how my toddler is in Stage 3 hypothermia.


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## ccwhite (Aug 15, 2009)

I've only had my new furnace with heatpump setup for one heating season. But What I've found so far is that With the new (R-410a) refrigerant I can let the heat pump run down to about 30 degrees. If it is going to go lower than that I fire up the wood furnace. My electric backup coils have only ever run for 5 minutes when we installed the furnace just to make sure they worked. They've not run since then.It seems to me that above freezing the heat pump doesn't use much more power than the draft and blower fans on the wood burner. This also stretches the wood pile very nicely. Again this is my observations from one heating season with the new equipment. Been heating with wood all my life but this is a new setup for me ... never had central air / heatpump before.


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## woodgeek (Aug 15, 2009)

I've been running an air source for one season....Webby's math is right on.  The HP is a LOT cheaper in the 30s outside temp, and probably still cheaper than pellets even down to the teens.  How the tstat is configured is key to savings.

The OP did not say what his back up was--is it only electric strip?  Or do you shut down the whole system and fire up some older furnace?

I've got an old oil boiler, and am in the situation that the HP is cheaper than the oil, which is cheaper than the electric strip. This is true (at current rates) even down to 0F.  So I run the HP at all temps, disconnect the strip completely (it runs on defrost cycle), and wire the boiler in as a second stage backup.  I dropped my seasonal oil usage by 70% using the HP this way, and netted about $900 at $0.10/KWH. A lot of people dis ASHPs because of old technology and bad installations.  They can deliver cheap heat in a lot of climates and temps.

If the OP only has HP, strip and pellet, he should make sure the tstat is configured such that HP compressor is still going at low temps, and just manually shut it down (with the "emergency heat" setting) under heavy ice/snow conditions that might clog the outdoor fan.  He should then burn pellets only at temps where the strip is getting energized as a backup (there should be a indication on the tstat), probably below 35-40F.


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## THE ROOSTER (Aug 15, 2009)

I have a Carrier Infinity heat pump and it is efficient to five degrees above zero, and with the price of pellets rising I can tell you that I will still be lighting my Harman when the temp. hits the 20's... There is nothing like the warm heat of these stoves and watching a fire burn when it's cold and snowing outside


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## dac122 (Aug 15, 2009)

If you have the COP chart for your Heat Pump and the AFUE of your pellet stove, and per ton cost of pellets, I can post back the exact calculations.  Contact the manufacturer for the COP chart.  Also, be sure your KWH includes taxes - just divide your total KWH used by your total bill.  And what is your backup heat: heat strips, gas furnace, etc., and its cost and unit efficiency?

With heat pumps there is the economical balance point and the comfort balance point.  The economical balance point is reach when it is cheaper to run another heat source such as when the COP reaches 1.  The comfort balance point, which is much higher, when the air temperature discharge is no longer comfortable or is reported by many customers as clammy/somewhat chilly.  Most HPs are set to fail over to backup heat around 35°F because of these types of customer complaints.  For the moment we will assume the comfort levels are the same between your stove and HP, but we know it is not, so you will have to factor that intangible into your decision.

I would not be surprised to find that your HP is good down to a certain temp, and your pellet more affordable after that, followed by your backup heat.  We can even calculate what temp that is depending on your COP chart, AFUE and fuel costs.  You will then know what temps to start lighting the pellet at, and even locking out the backup heat.


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