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Best options for replacing oil-fired steam radiator system in a 1850s home?

Joe Schmo | Posted in Energy Efficiency and Durability on

I just purchased a large multistory brick home built around 1850, located in Frederick, MD, and would like to replace the existing oil-fired boiler steam radiator system and electric AC system with a better arrangement to save money and safety.

There are two electric units currently; one in the basement serving the first floor and one in the walk-up attic serving the second floor. So far we are considering two new 16-SEER, 5-ton heat pump units but I am curious if you had any better suggestions. Any insight and guidance would be greatly appreciated.

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  1. Aj Builder, Upstate NY Zone 6a | | #1

    Schmo... nice name. Are you happy with the proposal? No matter what, the age of the home to me sets the cost you will always be paying for energy and for buying HVAC systems.

    What does "there are two electric units" mean?

  2. GBA Editor
    Martin Holladay | | #2

    Like A.J., I'm unsure what you mean by "electric units," but I'm going to guess that they are air handlers that distribute cool air for air conditioning.

    When it comes to heating and cooling an older house like yours, the reputation and skill of your HVAC contractor is more important than the type of equipment that is installed. Spend some time researching local contractors to get assurances that you have chosen a reputable company.

    As with any older home, there are probably opportunities at your house to improve the thermal envelope -- to reduce air leaks and perhaps to improve the existing insulation. These steps often represent important ways to save energy. If you are interested in getting this type of work done, you should consider contacting a home performance contractor or home energy rater to get an energy audit and energy retrofit advice.

  3. Joe Schmo | | #3

    What I meant was that there is a 4-ton electric air handler unit in the basement serving the first floor and a 3-ton unit in the attic serving the second floor. Both air connected to outdoor compressor units for AC and have electric resistance coils at the air handler units to provide back up electric heat capability. The house is surprisingly tight (relative of course) considering its age but my objective is to use the steam radiator/oil system only as a back up due to the large costs and safety concerns associated with using it. In this day in age, I think a well distributed, high efficiency system, e.g., dual unit, dual zone heat pumps, should be able to save us money over the oil-fired boiler and electric back up, no? In addition, insulation really isn't an option given the type of construction, i.e., two layers of brick with lath and plaster on the interior and no wall/stuff cavities/voids to insulate. I am considering some form of insulation in the attic though.

  4. Aj Builder, Upstate NY Zone 6a | | #4

    Joe what does a KWHr cost? Expect system COP 2. With mini splits and no ducts COP near 4 for your location as far as heating verses oil. What is your oil cost per gallon and gallons per year?

    One last thought. Not using your steam system it will still age....

  5. Kevin Dickson, MSME | | #5

    You may want to consider conversion from oil to natural gas, especially if there is no wall insulation in the house. Gas looks to be cheaper than conventional heat pump heat for now and many years to come. YMMV

    This has been discussed hundreds of times at

  6. Joe Schmo | | #6

    There is no gas service run to the house currently and that would still point combustion products in the house.

  7. Expert Member
    Dana Dorsett | | #7

    Any heating system upgrade starts with a heat load calculation, otherwise you won't know if the heat pumps are enough, too much , or (if dumb luck counts for something) just right.

    How old is the steam boiler, and what are the nameplate input & output BTUs?

    On a mid or late winter oil tank fill, look up the heating degree-days that occurred between the exact dates of that fill and prior fill. (You can download a daily base 65 degree-day spreadsheet from Try to find the weatherstation nearest you that has a complete dataset. ) Then we can figure out from fuel use against degree-days and the boiler's efficiency approximately how much heat pump it takes to get you there. If you have a regular filling service they will often stamp a "K-factor" on the billing slip, which is the same information, different format. (K-factor== heating degree-days per gallon, we're looking for BTUs per degree-day, which can be derived arithmetically.)

    If your house is on the gas-grid the cheapest solution would be to install a conversion burner, which would cut your source-fuel BTU cost by half. The efficiency as a system may still be pretty low though- some steam systems operate at less than 50% net efficiency (which would skew the fuel-use derived numbers too, but we can at least ball-park it.)

  8. Joe Schmo | | #8

    We pay ~5.429 cents/kWh and $4.3/gal of oil. The house is also roughly 4,200 sf.

  9. Expert Member
    Dana Dorsett | | #9

    If your electricity is truly that cheap (less than half average residential retail rete in MD : ) you could replace the steam system with resistance-electric heating and come out ahead. Take the electric bill, divide the dollars by the kwh, see if it's really that cheap. $0.05429/kwh sounds like the energy-only portion of the bill, not the delivery.

    For $0.05429/kwh you're getting 3412 BTU which so it takes 1,000,000/3412 = 293.1 kwh per MMBTU, at a dost of 293.1 x $0.05429= $15.91. If you were paying the statewide MD average of $0.1348/kwh it would be 293.1 x $0.1348 = $39.51/MMBTU, even without heat pumps. A ducted heat pump system with an average coefficient of performance of even 1.5 (the better ones would hit 3 in your climate), would come in at $39.51/1.5= $26.34/MMBTU. A better class ductless mini-split would average nearly 4 in your neighborhood, for a net heating cost of about $10/MMBTU.

    A gallon of oil has about 138,000 BTU, burned in an 85% burner it can deliver only 117,300 BTU/gallon, best possible case. That means it takes at least 1,000,000/117,300 = 8.525 gallons/MMBTU of heat delivered to the house, at a cost of $4.30/gallon x 8.525 = $36.66/MMBTU, which is BARELY cheaper than resistance- electricity at the average MD price. In reality with the standby and distribution losses of the steam system it would probably be slightly cheaper to go with resistance-electricity at the state average price. With 5 cent electricity you'd be paying well under half for heating than you are with oil. At a more typical 70-75% net operating efficiency your output per gallon is really more like 100,000 BTU/gallon, or 10 gallons/MMBTU, for a heating cost of about $43.00 / MMBTU.

    The square footage of the house is a somewhat meaningless data point. Heat loads are a function of exterior surface area (and material types, which have different thermal conductivities), air leakage, offset by internal heat sources ( humans & other warm-blooded animals, electric loads that run 24/7 like refrigerators, etc.) A 4200' house is probably not a likely candidate for heating solely by ductless heat pumps, but you might be able to heat 2-3 large zones with ductless, depending on the actual heat loads and the floor plan.

  10. Joe Schmo | | #10

    Without having the oil bill handy, I can tell you that we paid roughly $1,900 to fill (top off) two 275 gal tanks less than two months ago and those tanks are now empty. Our electric bill for this month was $1,400 (~15,500 kWh) so now you can see why we are considering what our options might be. The 5.429 number is the standard offer service electricity rate as of this month. The cost of two new 16-SEER heat pump units is just shy of $15k installed and the current AC units that the heat pumps would replace, which have an electric heat back up on them, were installed in 1999, for reference. The oil boiler is much older but in relatively good working order. As far as I know, the worst possible way to heat a home, especially one like this, is with oil and electric resistance heating.

  11. Dan N | | #11

    I'm just a home owner but I can tell you what I did after spending between $4500 - $6000+ a year on oil heat.
    I live in (N.J.) a house built in 1868 about 4000 square feet with hot water radiators ( not steam), when I bough the house, it had an oil boiler, I called in a guy who converted it to Natural gas, but also just as importantly, zoned the house. The house was originally on one big loop, now I have 5 zones and it makes a huge difference. I heat the rooms I need to heat, when I need to heat them, and the smaller loops are a lot more efficient and heats a lot more evenly. When the house was on one loop, the last few rooms on the loop were barely warm and the first few rooms were hot.
    Oh and I haven't broken the $1000 a year mark to heat - let alone the huge numbers I was spending.

    I'm not sure what your safety concern is with natural gas being combustible - but I suppose that's something personal for you to work out.

    but that's just my two cents, waiting on change

  12. Joe Schmo | | #12

    I would probably consider natural gas more if it were a easier option, i.e., there was a gas line nearby, but there isn't The products of combustion concern is just based on the fumes and products that are released into the house when used, mostly when cooking, but more so with having actual oil tanks in the basement. It really comes down to the fact that using oil for heat is almost cost prohibitive and not very sustainable and having everything electric might open the door to installing solar panels on the roof.

  13. Dan N | | #13

    Understood, but it might be worth it to see if the gas company will run a line, I know they did in my parents neighborhood after enough people on the block made a commitment to convert to gas - but it takes someone on the block to get people interested in change, something to think about.

    Also for cooking I went with an induction stove (electric) which I have to say was one of the best purchases I ever made - love it. It's amazing how fast water can boil - and no combustion .

  14. Aj Builder, Upstate NY Zone 6a | | #14

    I would never have bought that home if you could have bought another with natural gas and with more insulation, smaller whatever. Did you know that your utilities were going to be $20,000 annually when you purchased? And you figured when you purchased that somehow after the fact you could add in the cost of changing to heat pumps?

    Whole house air source heat pumps are not going to save you huge amounts.

    You best way to save would be to sell that home and buy something that has less costs. But you won't so... good luck Joe Shmo.

    Dan N, we did exactly what you posted, a neighbor started us all applying for NGas and we finally should be getting it after a few years waiting this year. Small homes with large central spaces should consider mini splits pellet stoves, zoning and of course lower temperatures is really needing to spend less. Pull out those sweaters that are tucked away.

    Joe Shmo, you may want to investigate ground source heat pumps... expensive but subsidized and they play well with ducting. I think GEO is by far your best bet if you don't sell.

  15. Joe Schmo | | #15

    I could live in a shipping container too but I won't. I could do a lot of things but selling a dream home that I just purchased is hardly a prudent move. The house is an amazing property that deserves to be lived in and preserved. It is an historic property that has stood many times longer than most houses being built today will. Its a challenge but one worth attempting considering it really is a matter of transitioning it from 19th century thinking to today's, i.e., tighten the envelope and incorporate modern technology for efficiency.

    We got estimates on the utility costs but they were either wrong, inaccurate (representative of fewer occupants), or otherwise misleading. We also suspect that our latest electric bill for $1,400 is an error. All indications are that we are much lower than that on usage, as in a third of that. My inquiry is how to go about waning the property off of fossil fuels and reducing costs in the near term. Suggesting that I install ng, when its not readily available, or a geothermal loop is cost prohibitive in the near term and seems a bit shortsighted in my opinion. Frankly, I am surprised that these suggestions are even being made on GBA. For instance, we might be able to install two new high efficiency, 16-SEER, air source heat pumps and a rooftop solar array for less than or about the same as a geothermal system and reduce both the electric expense overall as well as fossil fuel usage. I guess my question is whether anyone has a better idea.

  16. Kevin Dickson, MSME | | #16

    Here are your first two steps:
    1. Air sealing
    2. Tune up the steam system. Careful, 90% of licensed heating techs know absolutely nothing about steam.

  17. Expert Member
    Dana Dorsett | | #17

    "Our electric bill for this month was $1,400 (~15,500 kWh) so now you can see why we are considering what our options might be. The 5.429 number is the standard offer service electricity rate as of this month. "

    Do the math: $1400.00/15,500 kwh is 9 cents/kwh, not a nickel- the delivery charges make up the difference.

    A dumb non-modulating ducted heat pump with tested-tight ducts will cut that 15,500 kwh to under 5000 kwh for the kind of weather that occurred over the past month.

    Kevin Dickson has it at least half right- air-seal the HOUSE first, then air seal the DUCTS. Mothball the steam for now- see if the rest won't keep up with the load after building envelope improvements. With 9 cent electricity you're paying $26/MMBTU, which is quite a bit cheaper than the $36 / MMBTU you'd get out of a PERFECT oil-fired steam system. When oil hits $3 / gallon it would have a tiny edge against 9 cent resistance electricity in a near-perfect steam system but that's about it. It would take buck-fifty oil to compete with a heat pump at 9 cents/kwh.

    An out of tune steam system that you never fire up uses no more oil than a perfect steam system than you never fire up, so don't mess with it- you have better places to spend the money. Only if you HAVE to use the steam system to heat part of the house would it make any sense to work on it, but it might make more sense to install something else for heating those rooms/zones instead.

    Swapping out AC system + resistance heaters to full blown heat pumps with resistance backup you'd be well under $20 / MMBTU average, maybe even under $15, no more than half the best-case $36/MMBTU operational cost of the tuned up oil-fired steam system.

    As part of the air sealing effort, if you have a bunch of clear-glass windows that leak air (double pane or single), a tight low-E exterior storm window can make a huge difference in net performance at a much lower cost than a replacement window. A low-E storm can bring an antique single-pane wood-sash double-hung down to about U0.35 performance, and improves ~ U0.5 insulated glass windows to about U0.30.

    It would be an unusual house that presented NO opportunities for insulating walls anywhere without major renovation, and heat loss is a square feet x delta-T sort of thing- when you have R2-R3 walls every square foot counts. It's worth addressing the easiest stuff, and start at least thinking about what can be done for the next stage.

  18. Joe Schmo | | #18

    Thanks for the insight. And, yes, 9 cents is dead on for the net pricing. And to reiterate, the utility appears to be doing some highly questionable math to get that 15,500 figure. The total used for the house (on the electric heat mind you) for the last seven days (based on a new digital meter) is 1,000 kWh on the nose so there is no way we ever used the 15,500 thy're claiming. During the period where they claim we used 15,500, we used zero electric heat. We actually can't even run the steam and electric systems at the same time with the way things are currently wired. I suspect that if we do the heat pump install, the electric heating load will go up, perhaps add a couple thousands kWhs per month but will still be cheaper than the oil and will also reduce the cooling loads during summer.

    And I will certainly look into air sealing and insulation. There are a few opportunities in the attic and basement spaces but the walls of the house are two layers of bricks with lathe and plaster on the interior with no cavities in between so I guess I'm just not sure what, aside from rigid interior panels, would work for insulating the walls. The storms are certainly a good start though even though I am sure aesthetically they won't meet the boss's approval on every window.

    An interesting note is that when I was arguing with the electric utility, two separate people claimed to have never heard of "this new radiator heating system" that we had. I simply explained that it was how they heated houses for 100 or so years.

  19. Aj Builder, Upstate NY Zone 6a | | #19

    Why is GEO too expensive? What have you been quoted after rebates?

  20. Flitch Plate | | #20

    Go to if you like hot water.

  21. Flitch Plate | | #21

    Go to if you like hot water.

  22. Joe Schmo | | #22

    I haven't gotten a quote for this house yet but based on others' experience, I am assuming geo would be $30-40k.

  23. Expert Member
    Dana Dorsett | | #23

    I'd be very surprised (even suspicious about competence) if quotes for geo came in as cheap at $30-40K with loads as large as yours.

    A billing of 15,500kwh for a period which did not include any electric heating should be challenged. That much power use would show up as quite a lot of heat somewhere. That's 53 MMBTU, the equivalent of torching off 3 cords of hardwood in a wood stove, or 450 gallons of heating oil in a pretty-good steam system. You would HAVE to have noticed that much heat! (That is more than 2x the annual usage for my family of three, none of which is for space heating.)

    There are good/better/best storm windows. Harvey (a northeastern regional player) makes the tightest in the biz, and have a hard-coat low-E glazing option. Larson's "Gold" series low-E storms (distributed thought the blue & orange box store chains) are pretty good too. A low-E storm costs more than a clear-glass storm, but will pay for itself in about 1/3 the time on energy savings. (At your energy prices that would be about 3-4 years.) It'll pay for itself in one week on enhanced comfort levels. Larson also makes interior storm windows, but the net effectiveness on energy use isn't as high, and puts the original window at a slightly increased risk of rot/deterioration since it's now on the colder/wetter side of the assembly.

    Replacing 1500-2000 gallons of oil use with heat pump power will increase your power bill, but at ~$15 / MMBTU or less instead of $36+/MMBTU with the oil burner it'll be a significant overall cost savings.

  24. Joe Schmo | | #24

    The approach I am taking is to take the cost of electricity together with the cost of the oil and in doing so, I don't see how taking to two new heat pumps options doesn't save us money. It also sets us up to possibly power the whole house on solar later on.

    And I most certainly contested our recent outlandish bill. Somehow the number didn't strike them as high and they kept claiming that it was due to the cold winter but just couldn't understand how we were heating the house with oil and steam radiators. In the end, I convinced them that they had charged us for the previous owner's bad habit of running only the electric heat while the house sat vacant for many months. Our usage now (granted its not as cold) is on track to be about 4-5000 kWh per month and that is while using the electric heat.

    So it sounds like replacing the electric AC/oil boiler combo with new 16-SEER heat pumps is indeed the best course of action since natural gas is not easily available and oil is so expensive.

    Am I correct in envisioning us being able to power the whole house on rooftop solar for around $40k in addition to the cost of the heat pumps discussed above? I think that even if geothermal were more economical in our case, it only addresses the heating and cooling side of things whereas rooftop solar and the new heat pumps could be had for the same price leaving zero electric bills. I intend to explore the addition of some insulation and air sealing as well, e.g., attic insulation and storm windows.

  25. Expert Member
    Dana Dorsett | | #25

    At your heat loads it's unlikely that a PV array sufficient to cover your heating bill would fit on the roof. In Maryland you would get about12 kwh per year out of a square foot of south facing optimally pitched roof. If the heat pumps get you down to an average of 2500 kwh/month for 7 months of heating season, and after some air-sealing, duct sealing, low-E storms, plus attic insulation cuts it to 2000kwh month, that's still 14,000 kwh/ year, which would take 1200 square feet of optimally pitched south facing roof. (In fact I'm not convinced you'd get it down that low with ducted heat pumps and modest building improvements but you might get it down to 25,000 kwh/year.)

    In New England it takes a tight house with ~R40 walls and triple-pane windows and a highest efficiency ductless heat pump to be able to go Net-Zero with an array that fits on the house, and while your annual heating loads are only ~2/3 that of say Connecticut, your heat losses are 5-10x too big for that to be a credible option, and pretty-good ducted heat pumps run at about 2/3 the efficiency of a mini-split.

    Uninsulated brick walls are pretty lossy- you won't get there with air sealing, low-E storm windows, and attic insulation alone, but at least it's start.

  26. Joe Schmo | | #26

    So maybe we don't quite hit net zero but can we approach "pretty good?" We do also have the option of mounting some panels elsewhere on the property, maybe even on trackers. We have multiple fire places that could accept an insert or two to carry some of the heat load as well.

  27. Expert Member
    Dana Dorsett | | #27

    The multiple fireplaces are undoubtedly a significant part of your heat load, since they drive infiltration air 24/365, and drive hardest at the lowest outdoor temperatures. Not only are the flues themselves sucking air, the flue-chases are likely not well air sealed. Dealing with both the flues and the chases should be near the top of your air-sealing priority list!

    Iron flue dampers in the firebox literally never seal well. If you have smooth-walled terra cotta liners in those flues (possible, but not standard issue in 1850) they can be seasonally sealed with a "chimney balloon", but if it's brick that won't seal reliably. The flue chases are best sealed at every floor using sheet metal and fire-rated foam or mastic, but in many instances the best you'll be able to do is sealing it at the basement &/or attic.

    If you install a wood burning insert, insist on a sheet-metal air-barrier at the top of the old fire-box where the new code-required flue liner comes through. It's impossible to seal the liner your air barrier perfectly, but you can get it mostly there with an automotive type exhaust sealing putty. (It'll crack & crumble a bit over time, but better a small crack than a big hole.)

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