Sunday, February 22, 2015

2015 heating cost comparisons

A couple years ago I did some calculations to compare heating costs in Nova Scotia.  Since then energy costs have changed a bit, and I have more accurate information on the efficiency of oil boilers and pellet stoves.  As well I intend to add natural gas to the comparisons.

Electric heating costs have not changed much, with the cost of electricity now 14.95c/kWh.  This equates to a cost of 4.38c per thousand BTUs.

Furnace oil is now selling for 95c/L.  In my previous calculations, I assumed a 90% efficient condensing boiler.  These are uncommon in NS, so I'll use the 84% efficiency of an oil fired boiler with a tankless coil.  This equates to a cost of 3.14c/kBTU.  Pie anyone?

Instead of propane which is not commonly used for space heating in NS, I'll look at the cost of natural gas.  The current price of natural gas is $20.69/GJ.  When the $21.87 monthly charges is factored over my estimate of 42GJ/yr of gas consumption for a moderately energy-efficient residence, the total cost per GJ is $26.93/GJ.  With one gigajoule equal to 948 kBTU, and an efficiency equivalent to an oil fired boiler, natural gas heat costs 3.38c/kBTU.

For wood pellets, prices have increased so that 40lb bags are selling for at least $5.50.  I've also found out that wood pellet stove efficiency tops out at around 87%, and for typical units is closer to 75%.  After updating my calculations based on the higher price and lower efficiency, wood pellet heat costs 2.29c/kBTU.

With the recent popularity of air-source heat pumps in Nova Scotia, it is prudent to compare their cost of heat to other sources.  A high-efficiency unit with a COP of 2.4 will provide heat at a cost even lower than pellets - 1.83c/kBTU.  A lower efficiency unit with a COP of 1.4 will provide heat for about the same cost as oil - 3.13c/kBTU.

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