There was a period lasting a few weeks during which I had convinced myself to move to a propane system with a nice little modcon boiler. That abruptly ended when I realized that our house was somewhat under-baseboarded and we’d have to run the system at 180 degrees except for when temps were above 40 degrees or so.

If your situation is such that your house cannot efficiently take advantage of a condensing boiler, then propane becomes a tough sell, at least at the pricing levels here in southern NH.

BTW, I’ve been enjoying this site– lots of interesting content!

We use lots of condensing boilers up here because there’s so much radiant heat being installed. That runs a much lower water temperatures which makes those systems more efficient.

Thanks for all the input on an interesting conversation.

The U.S. Energy Information Administration says heating oil has 138,690 BTUs per gallon.

The U.S. Dept. of Energy says a gallon of propane has 91,330 BTUs.

If you accept these numbers, then heating oil has 51.8% more BTUs than propane. Put another way, a gallon of propane has 65.8% of the BTUs in a gallon of heating oil.

Also, (and I don’t mean to be annoying on this point), but it is a rare homeowner who will actually get (%% efficiency from a propane modcon boiler. You’d have to operate consistently in condensing mode, which would be impossible for any house with conventional fin-tubed baseboard, unless the installer put in at least twice the amount that is typical.

I called around and can’t find propane any cheaper than $2.89 in our area. Oil is $3.59. So I did some math based on all these numbers:

1200 gal of oil = 1200 * $3.59 + $4,308 at 100% efficiency, plus 15% extra for an 85% efficient boiler = $4,954

1200 gallons propane * 1.518 to get equal BTUs = 1,821 gallons @ $2.89 = $5,263 and added 10% (realistic annual efficiency of a 95% efficient modcon boiler would be about 90%)= $5,789

So propane would cost $835 more per year… or be 16.8% more expensive.

Using your pricing:

1200 gallons of oil = 1200 * $3.59 = $4,308 assuming 100% efficiency. Now add 15% to get to an 85% efficient boiler and you’ll be at $4,954

1200 gallons of propane * 1.36 to get equal BTU’s = 1,632 gallons. 1,632 * $2.92 = $4,765. Now add 5% to get to a 95% efficient boiler and you’ll be at $5,004.

This is based on your pricing. Where I’m at oil is running in the $3.75 range and propane last week was $2.75.

The point here is pricing is a wash in my cases. Always has been. If you look at BTU’s per dollar they are extremely competitive with each other. Price isn’t the issue at all.

Since it requires 1.53 gallons of propane to yield the same number of BTUs as a gallon of oil, that means you’d have to buy $4.46 worth of propane vs. $3.56 of oil.

Even if you allow that propane can burn 10% more efficiently than oil using a mod con, that still means that $3.59 worth of oil is the same as $4.02 of propane. So propane would be at least 11% more expensive.

But if you don’t get that full extra 10 percent of efficiency or buy less than 1200 gallons of propane a year (and have to pay more per gallon), it becomes even more expensive.