From the US Energy Information Administraion
Btu content of common energy units (preliminary estimates for 20211)
                  
- 1 barrel (42 gallons) of crude oil produced in the United States = 5,691,000 Btu
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- 1 gallon of finished motor gasoline (containing about 10% fuel ethanol by volume) = 120,238 Btu
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- 1 gallon of diesel fuel or heating oil (with sulfur content less than 15 parts per million) = 137,381 Btu
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- 1 gallon of heating oil (with sulfur content at 15 to 500 parts per million) = 138,500 Btu
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- 1 barrel of residual fuel oil = 6,287,000 Btu
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- 1 cubic foot of natural gas = 1,039 Btu
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- 1 gallon of propane = 91,452 Btu
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- 1 short ton (2,000 pounds) of coal (consumed by the electric power sector) = 18,934,000 Btu
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- 1 kilowatthour of electricity =  3,412 Btu
View attachment 772253
Fuel Oil No. 2     Gallon     $ 5.50    138,690   btu/gallon @75% eff. $5,287.57 per million btu.
Kerosene     Gallon          $ 7.59    135,000   btu/gallon @95% eff.  $5,918.13 per million btu.
Propane     Gallon            $ 3.12     91,333    btu/gallon @95% eff.  $3,595.86 per million btu.
Propane     Gallon            $ 3.12     91,333    btu/gallon @85% eff.  $4018.91 per million btu.
Electric (heat pump)  kiloWatt-hour (kWh) $0.18   3,412 btu/kwh @250% eff. $2,110.20 per million btu
or my supplemental heat being coal;
Coal   Ton(2000 lbs.)     $550.00    25,000,000 btu/ton @75% eff.  is $2,933.33 or just a bit more then my mini-splits
which are doing the heating at this time for me, coal will likely come on next week or so when it gets too cold for the mini-splits to maintain eff.
So yes this year propane would be less expensive then #2 oil,
So all I need to do is buy a couple of 1000 gallon propane tanks at $2500 -$4500 each,
And $2500 - $3500 for a new boiler plus installation and fill the tanks,
So for $10,000 to $15,000 I can have a new heat source that may save me $1500 a year