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Comparing oil fired boiler replacement options

harbin2 Member Posts: 2
I'm a little overwhelmed by all the options and variables involved in replacing my 14 year old EFM oil fired boiler with something that uses gas. I have a 2,000 sq. ft., poorly insulated, cape cod built in 1942 that has cast iron radiators. I live in south central PA and have been paying $500 per month for my oil heat and hot water. I've ordered gas.

I'm trying to calculate the 10 year cost for the following options:
1. A 95% high efficiency, wall hung "combi" boiler
2. Replacing the existing boiler and indirect hot water heater with new gas boiler and separate gas hot water heater (I'm assuming 85% efficiency).
3. Replacing the oil fired burner with a gas burner and keeping the existing boiler and indirect hot water heater (I'm assuming this will be 80% efficient)

My question is about how to convert efficiency into dollars. I realize there are variables like where I keep my thermostat set, the price of gas, etc. I'm roughly assuming that my monthly gas price will be half of what it is now (I WILL be raising my thermostat from 62 to 68). So, if my cost to run a high efficiency unit is $250 at 95% efficiency, what would the cost be for 85% and 80%?

Any thoughts or advice on the percentages I'm using or options I'm considering would be very much appreciated.


  • Jamie Hall
    Jamie Hall Member Posts: 16,596
    I presume you are talking about a hot water heating system? Otherwise a wall hung -- or any "high efficiency" mod/con boiler simply isn't available.

    May I give you a though from an old coot? Trying to convert efficiency into dollars is almost impossible. You are essentially making a bet on how fuel costs will vary over the next ten years, and how much maintenance will be, and variable costs of money, and so on.

    I will also say that the very best bang for your buck is going to be to do whatever you can reasonably do to get the house tightened up and insulated as much as is reasonable. That's the first thing to do.

    Second thing to do -- having done that -- is to figure out what the actual heat loss of the house will be (or if you plan on doing the boiler first, is) and, from that, how well the radiation which you have can match that heat loss. It may turn out that you have to run the radiation hot to keep the place warm -- in which case, again, a high efficiency boiler may not be appropriate.

    Then you can start looking at whether a high efficiency mod/con boiler will do the job for you, or whether you would be better served by a regular boiler, with its lower maintenance and first costs.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,188
    I'd spend the money on upgrading your building envelope, then size a new boiler to the new heat loss.
    For your size house, I'd recommend an Energy Kinetics boiler.
  • SuperTech
    SuperTech Member Posts: 1,670
    I agree with both of the above comments. Forget about a combi, a properly sized condensing boiler with an indirect tank is a better choice. It will require more work to install and will require more maintenance. Make sure parts are available locally. A cast iron boiler will last longer, cost less and requires more maintenance, but the AFUE ratings are lower. I believe Energy Kinetics makes a boiler that combines the best of both worlds, but finding a good installer is key.
    HVACNUT Member Posts: 4,084
    Agree with the other guys. Some utilities even offer a free energy audit. They'll do a blower door test and tell you what needs updating.
    Gotta due a heat loss calculation. Slant Fin has a free app so you can find out how many BTU's are needed to heat your home.
    Save for some applications, I'm not a fan of combi's. I just cant get past the fact that the boiler needs to be oversized to meet DHW demand. Kinda goes against what I was taught. But the earth keeps spinning without me I guess.
    Like @STEVEusaPA said, look at Energy Kinetics. Excellent boilers and many gas models to choose from.
    But you will need a certified EK installer.
    EBEBRATT-Ed Member Posts: 9,681
    I agree with all the above. If your existing boiler and indirect are ok for now the first step is doors, windows and insulation. Then an accurate heat loss to size the boiler to what your "new house" really needs. Put your $$ into that first

    Up grading the building envelope will save you more than switching fuels and changing the boiler

    Also look for energy rebates etc in your area. Sometimes the utilities offer rebates for upgrading the insulation, boilers etc.

    In that case your gas conversion may have to be done first or at the same time

    Post a few pictures of what you have now will give us a better clue
  • harbin2
    harbin2 Member Posts: 2
    Wow! This site is great and your responses are great too - THANK YOU! I'll take everything you say into account moving forward. I got a cheap infrared camera and have gotten insulation estimates but haven't started the process. That's going to cost more than a new heating source. I'm not in a BIG rush since the heating season is winding down. From your input, I think I should probably do a better job than I intended at quantifying my heat loss AFTER I insulate. I know gas prices could go up (seems like they would with increases in demand). Just changing the burner out involves some risks. I don't like the combi units either (water quality needs, high repair costs, still fairly new technology, etc.). When I take just the quotes I've gotten and MY VERY rough expected gas costs over the next 10 years, the costs are about the same for all three options. I just wasn't sure how far off my figures might be.
    Anyway, thanks again soooo much for your advice.