Comparing fuels

When it comes to heating there are several options of energy source. In New England, the most common are oil, propane, natural gas, electricity, wood, and the up-and-coming wood pellet. But how do you compare them? How good are they at providing heat? At what cost to the environment, or you wallet?

To do a comparison, you need to know how the fuel is measured (the unit):

Oil = gallons
Propane = gallons
Natural gas = cubic feet or therms
Electricity = Kwh (kilowatt hours)
Wood = cords
Wood pellets = tons

You also need to know the BTU (British Thermal Unit) per unit of fuel – the “heat value” per unit of fuel.

1 BTU = energy needed to change the temperature of 1 lb of water by 1° Fahrenheit.
1 BTU = approximately 252 calories.
1 BTU = energy generated if a 4”-long wooden match is burned completely.

So, the BTUs per unit of each of our fuels is:

Oil (No.2 and BioHeat) BTUs per gallon – 138,690
Propane, BTUs per gallon – 91,333
Natural gas BTUs per therm – 100,000
Electricity BTUs per Kwh – 3,413
Seasoned hardwood, BTUs per cord – 22,000,000
Seasoned pine, BTUs per cord – 15,000,000
Wood pellets, BTUs per ton – 16,000,000.

But of course, energy output is not the only thing to be considered. What about CO2 emissions?

Below is a list of how many pounds of CO2 each of our listed fuels emits per million BTUs (mBTU) generated:

Natural gas – 116.85 lbs
Bioheat (B20) – 131.04 lbs
Propane – 139.05 lbs
BioHeat (B5) – 153.80 lbs
No.2 (heating) oil – 161.27 lbs
Wood, dry – 213.01 lbs (if not from a sustainable reforestation source)
Electricity – (varies depending on fuel source)

Head spinning yet? The average 2,500sq.ft home in our region burns 800 gallons of heating oil each year. In so doing that oil generates 110.952 mBTUs and, as a bi-product, emits 17,893 lbs of CO2.

The table below shows how many units of each fuel will be burnt to keep the house at the exact same temperature as the 800 gallons of oil, and what the associated carbon emissions will be.

Natural gas | 1110 therms | 12,963 lbs CO2
Bioheat (B20) | 800 gallons | 14,540 lbs CO2
Propane | 1215 gallons | 15,424 lbs CO2
BioHeat (B5) | 800 gallons | 17,064 lbs CO2
No.2 oil | 800 gallons | 17,893 lbs CO2
Wood, dry | 5 cords | 23,634 lbs CO2
Electricity | 32,509 kWH | (varies according to source)

Of course, there are many other questions to ask: where does the fuel come from? Is it from a sustainable source? American produced? How was it transported? And how efficient is a particular heating system? All the above calculations assume 100% efficency, but even a brand new Energy-Star rated propane or oil furnace or boiler will be no more than 96% efficient and an older furnace or boiler, even one in good shape, could be as low as 75% efficient.

It’s a complicated business, but if you’re interested there are many energy calculators on the web and it’s fun to put in your consumption numbers and start doing some comparisons. One such is an interactive Excel spreadsheet provided by the Energy Information Administration. In the meantime – here’s to spring temperatures and turning off the heat!

Comments 2

  1. Kyler Brown

    I’ve actually been comparing different heating options for my cabin. This post was very helpful, especially because I love being able to compare different options. The table showing how many units of each fuel will be burnt to keep the house at the exact same temperature as the 800 gallons of oil is exactly what I needed to see. Thanks!

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