Comparing Heating Systems
A by-the-numbers look at the cost and efficiency of three types of furnace and two heat pumps
The big difference between all these systems is what powers them, but different kinds of fuel are measured in units that are hard to convert. To compare them meaningfully, we have to reduce them to a common unit: the British Thermal Unit, or BTU. (If you’re curious, it is the amount of heat required to heat one pound of liquid water by 1° F from a starting point of 39° F.)
With this yardstick, let’s see how some of the most common heating systems compare. We’re mainly going to look at unit cost, installation cost, efficiency, cost per million BTUs, and maintenance costs.
Heat pumps
Heat Pumps usually have a Coefficient of Performance (COP) of 2, which in furnace terms means 200% efficiency. Based on the approximate average cost of $.11 per kWh, the cost per million BTUs is $16.12.
Geothermal heat pumps are more expensive all around. Efficiency is on average higher than air source, with a COP of 3.5 on average. The 150% higher COP lowers the cost per million BTUs to about $9.21. The efficiency savings on a geothermal heat pump often allow homeowners to finance them and spread out the cost over time.
Air or geothermal, heat pumps are so efficient because they don’t have to generate all the heat they deliver. They instead take it from the outside air or ground, even when it’s cold. A heat pump that extracts the heat from the surrounding air becomes much less efficient when temperatures drop below 30 degrees F.
Oil
The heat conversion efficiency, which in conventional furnaces means how much of the energy put into the system is turned into usable heat energy, is about 80%. The cost per million BTUs $26.81.
Natural gas
The conversion efficiency depends on which system you buy, but on average is 85%. Every million BTUs cost about $14.47.
Propane
The heat conversion efficiency is 85%. The cost per million BTUs is $34.04.
The labor cost for furnace installation is about the same regardless of type; it’s basically the same work either way.
Unfortunately, there is still no universal answer to “what is the best heating system?” But if you’re looking at a new system and trying to compare types, we hope this has helped.