Reality check on oil vs propane vs electric boiler

johnsopaJanuary 24, 2012

My wife and I are purchasing an old (pre-1800's) farmhouse. It's had rooms added (out and up, it looks like) along the way, of course.

Total sf is about 2100. There is old blown insulation in the attic. Not sure yet about the walls. Current heat is via oil boiler to baseboard hot water. Central AC was installed (air handler is in the attic) awhile ago. House is likely pretty leaky so the guestimate is that it'll take about 4 tons (roughly 50k BTUs) to heat the place.

We really do NOT like forced air heat. We DO like floor-based radiant heat but likely will not rip up the floors to install it at this point.

New property has a 40x60 pole building that faces SSW. I am considering having solar electric installed (about 1200 sf generating about 15 - 18 kW) which I'm told will be around $40k - $505k less 30% tax credit and $7k of PA state rebate.

So, I'm considering adding a boiler in -- either electric or propane. We can't get a gas line to the house.

Here are the unit costs I am using based on research:



91k BTUs/gallon



139k BTUs/gallon



3400 BTU/kWh

Based on these calculations, I am getting costs of:

Propane: $0.0315 / 1k BTU

Oil: $0.0284 / 1k BTU

Electric: $0.0239 / 1k BTU.

I was always told that electric heat is going to be much more expensive than oil or propane, but this math is not showing this to be the case based on costs in our area.

In theory, on sunny days, it looks like the 15 kW solar system would fully run the electric boiler (50k BTU / 3400 BTU per kWh = 14.7 kWh) but of course we'd have some buy days and some sell days.

Am I missing something? This really seems like a no-brainer to me and whenever things seem that way, I get worried...


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Are you figuring in all the costs of the electricity, surcharges etc., and not just the raw energy price? If you are going to heat with solar, go with solar thermal. Solar heat with photovoltaic is too expensive by comparison.

I think that ground-source heat pump will be less expensive than an electric boiler in the long run, but it is a big investment up front.

    Bookmark   January 24, 2012 at 7:02PM
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Your PV is too shockingly cheap to believe. Where I am, you get about 6kw for $30k.

Nowadays, in many places electric is cheaper to heat with than oil and propane. Historically this was not the case. We have an unusual situation where NG is so cheap that electricity can generated with NG and still be cheaper than oil heat.

Obviously a heat pump is far cheaper to run.

Solar thermal is usually about 10% of the cost of PV for similar BTUs. PV prices are down enough that it might be 20% now. You have to balance that with the fact that PV is good all year around but in your area, solar thermal probably still makes more sense.

    Bookmark   January 24, 2012 at 7:22PM
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On second bought, in PA they might have to use evacuated tubes rather than cheaper panels for solar thermal. That would jack up the price considerably. It might still be less than PV.

I did not do the calks for the OP's PV price. I agree with david cary. Check solar for price trends.

    Bookmark   January 24, 2012 at 8:03PM
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I prefer calculations done on a cost per kW of heat delivered into the home. Your calculations don't seem to indicate at what efficiencies. We know that electricity is 100% efficient, but what about oil, propane and NG?

I would suggest investigating geothermal as well. Geothermal can heat without forced air and without ripping up your floors. What type of baseboard heaters do you have, aluminum fin or cast iron?

For the same cost of 'Electric: $0.0239 / 1k BTU', you could have Geothermal: $0.005975 / 1k Btu. Very hard to beat!

Geothermal also represents a system with much lower maintenance costs than either solar thermal or PV. No outdoor systems or components exposed to wind, hale, ice, vandalism etc.

Of course like PV, you would be looking at a lot of money for the installation.


    Bookmark   January 25, 2012 at 12:58AM
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I highly suggest taking a look at anthracite coal. Significantly less expensive to operate than the other options mentioned, historically stable prices, and 100% domestic fuel. With a modern EFM, Keystoker or other automatic stoker furnace/boiler heating with coal can be relatively hands-off and save you a lot of money over your ownership of the home. Check out Even if you're not too interested, it deserves a second look. most coal central heating systems can be configured from the factory to come with oil/ng/or propane backup.

As a backup, with NG not available, I recommend oil over propane or electric. Oil will always average less $$ per btu than propane and even high efficiency propane appliances don't make this up. I think you should double check your electric rates; I don't believe there's anyplace in the northeast (outside of plattsburgh ny and some other municipals) where your electric rates are in the $.08 range.

    Bookmark   January 25, 2012 at 2:51AM
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If you have central air, you should upgrade that to a heatpump. I know you don't like forced air heat but you should just go with it anyway. Its not that bad. You will save a bunch on energy costs. New single stage heatpumps are very efficient and will save you money on energy. They should atleast be used when its mild out.

    Bookmark   January 25, 2012 at 8:50AM
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berlin, why would coal need back up by another fuel?

neohioheatpump, the ac is likely set up to be cooling only and not work well for heat (attic hair handler and ceiling vents). Given that this is a very heating-intensive area, it might not be an acceptable solution. It is hard for me to accept any change from hydronic heat to forced air anything close to an "upgrade".

    Bookmark   January 25, 2012 at 11:04AM
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you need a "traditional" backup fuel for any kind of solid fuel heating. Solid fuel heating is considered a supplementary heat source (even if it's pretty much all you use) and a heat source that requires no attention is the primary heat source. Most homeowners' policies require something other than solid fuel heat to be present and be considered primary heat. Additionally, if you are away from home for an extended period, you will want to have a 100% maintenance free backup.

Often, these two fuel sources can be combined in the same unit - most on the market today offer that ability. Thus there is no need to have two furnaces or boilers sitting beside each other and the associated costs that would create.

With anthracite coal heat, the initial investment is usually far less and the payback much faster than most other "alternative" energy options. Anthracite coal heat is not for everyone, but, with the modern appliances on the market and the significant cost savings, it's an option that's worth looking into.

    Bookmark   January 25, 2012 at 7:19PM
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I know there is a bias against forced air. While an attic air handler and ceiling vents are not ideal in a/c or heat, the hit to efficiency is less than 20%. When you are starting at 300% with a heat pump, the 20% still puts you way ahead of the alternatives.

A well designed forced air system is not bad - it is fantastic really. Ok well - hydronic is better but I bet you can't tell when my system is on without you ear or foot on the register. The humidity is always around 40% with a humidifier. Sure hydronic is more efficient but given that you are sacrificing a heat pump, that is far more of an issue.

I think when you are looking at $5000 a year for hydronic vs $2000 with a heat pump, you might decide that forced air isn't that bad.....

And of course geothermal is a decent option.

I am just guessing that someone who is considering PV, it not someone who would heat their house with coal. But I could be wrong.

    Bookmark   January 25, 2012 at 7:37PM
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Not just "coal", david_cary, but anthracite. Phoebe Snow would certainly approve, and the OP appears to live in the land of anthracite.

All jokes aside, it would be interesting to know how many new coal furnaces and boilers are being installed these days.

    Bookmark   January 26, 2012 at 3:38PM
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