I have an oil fired forced hot air system for my home which is only about 4 years old ( the oil furnance, not the house). Anyway, I need to replace the old 10 seer AC system with a new 14 seer unit. I’m thinking about installing a heat pump system which uses the oil furnance as the cold weather back-up (below 35 degress). Does this make economic sense ( price of oil verses electric)? I’m in the Mid-Atlantic region.
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cold weather back-up (below 35 degress).
gotta know your electricity rates. At 10 cents kW-hr, it would not pay to run the oil until you are down to below 10F or even below zero.
That was the kind of reply I was hoping to get. Does anyone know of a chart where I can plug in the outside air temp, the price of oil, the price of electric, and do a comparison on cost? I know the new heat pumps are a lot more efficient but I'm still unsure at what temp to have the oil kick in. Thanks
here is a home-made excell spreadsheet, if you can open uS office stuff, you will have to figure out how to work it, dont have time this week for a tutorial.
This was for a house in Spfld IL, very low elec. rates, just about instant payback!
First you need to check with your power company and find the actual INCREMENTAL RATES for electric heat.There are all kinds of different systems. Where I am after a certain usage level the increment rates drop about 1/2 during the 8 "winter" months. And that is what I would be charged for a heatpump. Not the "average" per kWh rates..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I tend to disagree ... heat pump decision should start with ... is it right for the climate and THEN compare energy costs (be sure to include the relative efficiencies in calc'ing the cost per thermal Btu).
If I recall, heat pump efficiencies go south around 35-40 deg. If you have lots of time below that in the winter, it may not be worth it. If your climate is mild like Seattle, it's great (heat pumps)... but Minnesota would not be a good climate. Not familiar w/ winters in the mid-Atlantic.
I tend to agree with what you said. However, if in fact heat pumps lose their thermal advantage below 35,but are really efficient above 35 and you also have AC with the unit, what is the drawback to using a heat pump/AC unit with an oil or gas back-up below 35 if your winter climate has many days below 35?
Heat pumps can be 3-400% more efficient than resistance heat. The operative word is CAN.
Approximately a 1000 watt wall heater will give you about 3500btu's. Under optimum outside conditions a heat pump for every 1000 watts of energy to run the compressor and fan you should receive say 12000btu's of heat. Don't forget you are still paying for electricity for the heatpump and the furnace fan.
Outside temperature and moisture affects the heat pump efficiency. The cooler it get outside the efficiency start to go down immediately.
If you use an electric(back up) furnace as an example the outside temperature can go down until the efficiency of the heatpump matches the cost of running the electric furnace. So, the efficiency of the heatpump start dropping from 400% down to 200% down to 100%. Once it goes BELOW 100% THAT 'S the time for the heatpump to shut off and the backup heat to kick in.
Years ago when we installed those things they operated well into freezing temps but now they shut off above freezing. When asked an installer said "we shut them off because they are not as efficient". Of course they aren't but at 50F they weren't as efficient at 60F or if it is raining outside . A good chunk of the heating season is lost and I believe the so called payback time is greatly exaggerated. Add high yearly maintenance and high repair costs let alone getting qualified service people heat pumps are expensive.
As much as I don't like baseboard heat, they are 100% efficient (no heat lost) and almost maintenance free.
I still have most of my HVAC equipment, can buy wholesale, install myself, live on the west coast and I still won't put one in.
Just my opinion.roger
still have most of my HVAC equipment, can buy wholesale, install myself, live on the west coast and I still won't put one in.
You be throwin' money away. I'm just outside Seattle, it got to 17 F ( -8C) this winter and heat pump COP was still over 2.1.
Is BC hydro still under 3 cents kW-hr to still have only baseboard??? With DIY install of a split system, etc, your payback time even at 3 cents kW-hr would less than 2 years.
We are over 6 cents per Kilowatt Hour. All the heat pumps I have seen here (just a few) are cutting out between 5-7C and that is factory set supposedly. Apparently there would be warranty issues if you lowered the cutout temp too much. At least that's what I'm told.
If the pump isn't working a good chunk of the winter which is where your major savings would be, a pump doesn't make sense.
For the average person it would cost say 5 grand to install a pump into an existing ducted system. The yearly maintenance fee was about $185.00. I've seen quite a number of units out here die at about 10 years.
Over 10 years your maintenance contract, if prices stayed the same, would be almost 2 grand. Even if the system didn't die chances are you would require some repair in that 10 years but 20 years for a unit would be close to the limit. I know some last a little longer with heaps of service but I've changed a lot less than 10 years even after lots of service. The repair bills I would give to customers were high and yet they usually repeated the mantra that the pump was cheap to operate. NOT when you factor in repairs and maintenance
It's not as if a heat pump completely replaces other heat it is only and add on. People tend to factor their complete heating bill and then factor in their pump as though it worked all the time. It doesn't. Also if you had a furnace (oil, gas or electric) you would still have maintenance and repairs on that which is why I sort of like baseboard heat. Compare the cost to rarely if ever replace a baseboard heater to any other heating system. When dc motors came out in high efficiency furnaces, fan motors cost $800.00 and I think that was our cost!! All winter long we repaired gas furnaces. Day in and day out and we weren't the only company in this small town.
In Ontario where we had lived the hydro costs were very high and any form of electric heat was rare.
What I'm saying is that you do a numbers crunch on all the figures starting with getting at least some interest on the $5000.00 and not only focus on operating costs.
Now if I could get a pump REALLY cheap I might consider putting one in.
As I get older I tend to think that when I die I don't want to saddle the wife with a complicated heating system where the chances of being talked into a "more efficient) system is very real.roger
The 2 yr payback was for DIY install. Agree that if not DIY then cost can be 5X higher.
Did not know BC rates had gotten that 'high' <G>
Take a look at my spreadsheet on a very early post on this thread for calculations. For your own financial well being, think it would be worth your while to consider installing a HP.
Took the effort to get my EPA (USA) freon license and installed HP for slef, brother, mother, and son. Each system cost less than $1800 for 3 or 4T system. Mother got a rebate in central IL so total install cost (DIY) after was under $1K for a 4T system. Own system is 10 years old and not a bit of maintenance. edit: other than changing filters, of course!
I always disconnect (separate breaker and thermostat) for the resistance heat elements. Defrost does blow cold air that way, but bigger savings. I have never needed to connect the resistance heat in Seattle area.
Edited 5/28/2008 5:31 am ET by junkhound
I'm told that BC hydro rates are subsidized by the government and should be a lot higher. I think ONtario is around 8 or 9 cents but I forget. Another thing they do here (Canada) to keep the rates down they crank up the "transmission fees" or "accounting fee's. The hydro companies must apply to some government agency to be able to raise their KW rates but apparently not if it is those "other" fees.
I bought a house here on the island to flip and I put in all natural gas appliances ( I have gas licence). Hadn't checked into gas prices because I was going to flip it anyways. Stayed over a winter while renovating it and couldn't believe how high the cost was. Can't remember how much a gigajoule(metric cost) but it is higher than the mainland. Wife never liked gas anyways (she can smell a fly fart at 300 yards) so we don't have gas where we are now.
If a manufacturer would make a heat pump without the a/c mode I would really consider it. Here where I live a/c is not needed but heat is. I really like uncomplicated stuff and if a system didn't have a reversing valve and all the other stuff to make it work both ways it would be as simple as central air to repair. As I have been in repair service for different products I see things rather differently (maybe wrong) where even a relatively minor repair can cost hundreds and that cost should be factored into "heating costs". I seem to think a service call now is over $100.00.
Thanks for the response though, it gets me thinking.roger
Roger,
You're right ... if your HP doesn't work a large percentage of the winter, it's not saving you much. But the Seattle area is a fairly ideal climate. Not sure about how much colder up there in BC it is where you are at. I suspect it is still pretty mild relatively speaking.
Generally you shouldn't run the heat pump at colder temps ... especially in humid areas as the condenser can ice up ... and then you spend a bunch of money heating it back up to thaw it out.
In the right application, properly maintained, and properly operated, the heat pump should give you good service ... economically.
Your elec baseboard is maintenance free ... but you pay your money, you take your choice.
Also, if you have a cooling load, the HP provides that in the summer ... maybe you don't have to worry about that up there? But that is the other issue ... if you don't have a cooling load, using a heatpump for only heating seems a little pointless.
Are you sure that isn't minus 5 to 7 Celsius? If not, there must be a huge difference in different heat pump abilities and efficiencies. Our pump starts struggling around -12, but still doesn't require the propane backup. In fact the propane burners haven't run since testing at installation time. Our pump is a modest 11 SEER four ton American Standard.Here's an interesting article that suggests that even at -15, heat pump costs compare favourably with the cost of electrical resistance heating:http://www.oee.nrcan.gc.ca/publications/infosource/pub/home/heating-heat-pump/asheatpumps.cfmScott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.â€
No they are PLUS 5-7C. That is what shocked me so much. I'm used to them working as you describe. This PLUS 5-7C has to be manufacturer specs because they now come built in with an outside thermostat. We used to add them on if the customer wanted it. I guess they use thermistors also and can adjust the outside temp from the super-high-tech-no-homeowner-can-operate digital inside thermostat.
A friend of mine who has a brand new home called the builder who sent over the HVAC guy to adjust the outside temp from the inside thermostat. There was nothing in the thick operating instructions that came with the inside thermostat how to lower the outside temp.
This was being done ONLY because I had mentioned to my friend how stupid it seemed to me to be shutting off so early. The tech played with the Tstat and only lowered it to PLUS 3C because he didn't "feel comfortable" lowering it more! It would be interesting to see how low he could have lowered it.
I wonder if it is a manufacturers way of maintaining their warranty on the sealed system. Hell if they had a cutoff temp of PLUS 15-20 they could give a much longer warranty;)roger
Wow. That seems pretty weird to me.>>>Hell if they had a cutoff temp of PLUS 15-20 they could give a much longer warranty;)True enough.Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.â€
As others have indicated, it depends on your electric rates. I am in the Phila. region, and as a heat pump user ( with oil fired hydronic back up) I enjoy a whole house ( not just heat pump) electric rate decrease of aprox. 50% during Oct-March. Makes sense in my application.