Oil vs Propane
We live in Northwestern Connecticut in a circa 1800’s house, approximately 2500 sq. ft. The house is drafty in places although we have insulated various rooms along with the attic and have installed a number of new double pane windows. We have an oil fired forced hot air 14 year old Thremo Pride furnace (125 BTUs per hour). Our oil tanks are 30 years old and we have reached a cross road. Do we replace the tanks and continue with oil heat or do we replace the furnace and switch to propane? Regardless of that decision, we will be installing a whole house air sourced heat pump this year which will be used in the shoulder seasons. The furnace will be the sole source of heat during the winter months. The electric costs will be offset by a ground mounted 8.715 kWh solar electric system that we installed last year.
We welcome any thoughts or suggestions on the oil vs propane question.
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Replies
Why wouldn't you use the ducted heat pump for everything? It's a very good and efficient way to heat a house. I'm a designer in Maine and we use ducted heat pumps on more than half of our projects these days.
Hi Mike - We have not considered using only a heat pump for a couple of reasons. It can get very cold where we are depending on the winter and our house is insulated in spots but far from a newly constructed house. Also, we have not heated with a heat pump before and understand the heat delivery feels quite different than a forced hot air system. Overall, I think we’d be more comfortable sticking to our plan. However, you raise a good question and I’ll explore that as an option. Thanks. Jim
The newer heat pumps (such as the Mitsubishi HyperHeat units) are very much more capable of working in colder temps, and the old "heat pumps don't work in the cold" doesn't really apply anymore with those. The heat delivery is still warm air, but not so much hot. A conventional furnace blows relatively hot air for relatively short periods of time, which is how the furnace cycles. The cycles get longer and more frequent as it gets colder, because the amount of energy the furnace puts into your home is related to the length of time the furnace runs for in each "on" cycle. The furnace always produces the same number of BTUs.
A heat pump is different in that the air is warm, not as hot, but typically runs ALL the time. The unit will "modulate", varying it's operating parameters, rather than doing hard on/off cycles like the furnace. The end result is the same though, and the heat pump will maintain your set temperature indoors. The one thing heat pumps aren't so good at is doing things like setbacks, since heat pumps like to maintain a temperature -- keep it constant -- they are not as good with cycling between a high and a low setpoint (i.e. keeping it colder and night and warmer during the day).
Heat pumps generally get you air conditioning "for free" too as part of the system, which is handy to have even if you only use it ocassionally.
All that said though, if you still don't want to try a heat pump, and I really think you should (and keep in mind that Michael Maines is a long time contributor here who works in a pretty cold climate, so he has personal experience with what you're asking about), I would probably go with a propane system. Propane systems won't need burner cleaning the way oil often does, and propane gives you the option to use propane fired water heaters and cooktops too if you want. I don't think there is a big cost difference between the two fuels, but it will vary over time.
Bill
Jim, northwestern Connecticut is a considerably milder heating climate than where I am in Maine. We're around 7,500 HDD here versus roughly 5,500–6,000 in your area. Cold-climate heat pumps do lose efficiency as temperatures drop, including from defrost cycles, but they can certainly provide heat through a Connecticut winter. The system does need to be designed properly, ideally using a room-by-room load calculation rather than sizing it based on square footage alone. Your electricity costs are about the same as ours, and with your solar I'd at least look at the numbers before investing in new oil tanks or a propane furnace.
Connecticut has very expensive electricity. I helped a friend evaluate a heat pump vs heating oil there and we just couldn't make it pencil out.
Granted that was a couple years ago, oil has gone way up. But so has electricity.
It takes some getting used to heat from a heat pump I would be afraid that if one has the option to push a button and make 130° come from the registers instead of 90° air not everyone will resist the temptation to push the button long enough and adapt to the heat pump.
The other question is how much of the 125KBTUs do you actual need on the coldest day of the year. Consider clocking what percentage of the time the burner runs on the coldest days and or running the calculation from this article.
https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler
The low-cost option would be to put the existing tank in a containment pan.
I like my heat pump in my tight well insulated house.
Walta
Hi Everybody -
Thank you for all the information on heat pumps. You have given me information I had not considered and will use it in making our final heat pump decision. I still think we will probably use the heat pump for the shoulder seasons only.
Also, I’d say we may be leaning toward the propane furnace but it is still an open question in our house. We still need to get some quotes on the cost of purchasing a 500 gallon propane tank and whether it should be an above ground installation or an underground one.
Jim
Jim,
One advantage of propane is the resiliency it brings. In power outages you can still have heat, cooking fuel, and electricity if paired with a propane generator.
Note that nearly any natural gas fueled device, including generators, can usually be adapted to propane with an oriface swap. A lot of equipment is switcheable or includes what you need to convert it between those two gaseous fuel types, so propane does give you a lot of options here that you wouldn't have with oil.
For the OP, there is no reason aside from cost that you couldn't put in a heat pump AND an oil or gas fired furnace. You could then use the heat pump most of the time and the fuel-burning system the rest, in whichever combination is most comfy and/or most cost effective for you.
Heat pumps are generally most cost effective in areas with high fuel prices, especially if electricity prices are relatively low. In my area, we have very cheap natural gas available, and higher electricity prices, so heat pumps are not as economical in my area.
Bill
Propane is generally the highest cost per BTU on average and his the most price variability fuel.
The tank purchase / lease decision is a huge factor. Often a supplier will provide the tank for “free or leased” but only that supplier will fill the tank they own and they have a higher price per gallon for the customers with “free” tanks.
Seems like every fuel choice in Connecticut is going to be very high. Do the math and find your local prices for each fuel and divide by how many BTUs per pricing unit.
Walt