Comparing heating fuel costs

Last week I put up an article on the Basics of Home Heating as an overview of the different methods people employ to stay warm in the winter.  Today, I'm going to run some numbers showing a cost comparison of heating with natural gas vs. heating with electricity and provide a calculator that you can use to compare the costs of two different heating methods.  The calculator will give you an idea of how much it would cost you to heat with a different type of fuel, in order to get the same amount of heat output as you do with your current heating method.

Keep in mind this is for comparing two different fuels in a furnace.  The comparison gets a lot more difficult when looking at other heating methods like a air-source heat pump, geothermal heat pump, solar thermal radiant heat, etc.

You can press "Click to Edit" on the top of the calculator and then change the values in green if you have heating sources other than natural gas and electricity.  The values in orange will then update based on your changes.  In order to compare two different sources of energy, you are probably going to have to account for a conversion factor.  For example, in the below calculator the preset comparison is natural gas to electricity.  On my bill, natural gas is measured in therms, and electricity in kWh, so I had to use the conversion factor of 1 therm = 29.3 kWh.  To find conversion factors for all kinds of energy you can go to Online Conversion for Energy.  Using the conversions, you are able to convert all sorts of different energy sources including: Gallon of Residential Fuel Oil (U.S.), Gallon of Diesel Oil (U.S.), Therm, kWh, etc.

Please note that I am comparing electric resistance heating below, not an electric heat pump. (Refer to the comments for some information regarding this issue).

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Let's go over some of the items in the calculator above.

In the "Unit" column I put the units that the fuel source is expressed in on the bill.  If you use heating oil and buy it by the gallon, this would be in gallons. In the "Price/Unit" column I put the amount I pay the utility or fuel provider for each unit, not including any service fees or taxes.  You can find this stated amount on your bill.

In the efficiency column, put the efficiency of your furnace/boiler/space heater.  The DOE Energy Savers page has a nice section on furnace and boiler efficiency.  I know that my natural gas furnace is not super efficient, but it is relatively new, so it is around 80%.  I also know that electric furnaces (and space heaters) are almost 100% efficient because almost all of the electricity is converted to heat, so I used 97%.

When you are finished filling out all of the information in green, you can see the price comparison in orange.  If I were to use electricity, to get the equivalent heat output that I use in natural gas, it would cost me 4.44 (.097/.022) times more money (based on current natural gas and electric rates) !

One reason electricity is so much more expensive to heat with is that it has already been converted from a fuel once (at the power plant).  When you use it in an electric furnace, you are converting that electricity back to heat, which adds in inefficiency.  Not only that, but the electricity has to get to you from the power plant, which also means it loses efficiency. Natural gas is used right there in your house, so it doesn't lose any energy in transportation.  And while natural gas rates might fluctuate more than your electricity rate, over the long term, as natural gas rates rise, so will electricity rates because natural gas makes up about 20% of the nations mix on the electrical grid.

While it's not always easy to compare different heating methods, hopefully the calculator above will help you start to think about some of the variables; which include the cost of the fuel, how much "heat" the fuel contains, and the efficiency of the boiler.  When you are considering upgrading to a new heating system, ask your home contractor, energy professional, or sales person to help you with an analysis like the one above.  If they can't do that, then find one who can!

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Anyone familiar with ground source - geothermal technology knows that a properly designed system has 0 chance to freeze a neighborhood. There are many neighborhoods that are 100% zero and are having absolutely no issue. There is no chance on a residential application, unless the design and installation were both done improperly. Even in the worst case, only a small area would be impacted and could be rectified very easily.
Wow, what a difference they make... I've just phoned my mom and dad to have a discussion on their usage -they need help greatly to convert their old boiler room to more green efficient one. So using an electric heater for water pump would be ideal to save more money...? That's what my understanding is so far.
ckmapawatt's picture
Hasan, I don't think we're saying using an electric heater for water pump is the best way. What Eric was saying was than an electric, air-source heat pump is much more efficient than electrical resistant heating. Here's our post on an <a href="" rel="nofollow">air-source heat pump</a>.
ckmapawatt's picture
Great points Eric/Steve, I updated the following to let readers know this only includes the comparison of fuels burned in a furnace. In that case, all costs associated with the blower motor come in after the fact. When comparing a fuel in a furnace vs. a heat pump, things get a little more difficult and a more advanced calculation is needed, probably best done by a home energy professional!
There are lots of great back-of-the-napkin sketches in "Sustainable Energy - without the hot air" by David JC MacKay For example, discussing home heating &amp; cooling: He talks about the mini-split heat pumps: "One of these Fujitsu units can deliver 3.6 kW of heating when using just 0.845 kW of electricity. It can also run in reverse, delivering 2.6 kW of cooling when using 0.655 kW of electricity." He also points out that it may not be feasible for an entire neighborhood to use a ground-source heat pump; there is of course finite heat in the ground (it's not geothermal, not that deep) and you could well just freeze the ground, unless you put the heat back in in the summer... :)
ckmapawatt's picture
I really liked that book in how it simplified many of the calculations and brought logic into the discussion on clean energy and conservation: What the back of the napkin sketch can't tell you is how much heat you'll need when the outside air temp dips below 35 deg. F and your air source heat pump can't heat your home. It seems that this winter (in the U.S. at least) has been pretty nasty and those with air source heat pumps with electric back up may be worse off than if they had just gone with all natural gas to begin with!
Agreed. For some reason I was thinking about this as I put my kid to bed tonight, listening to the circulation pump run on my boiler ... ;) Could you integrate a heat pump with gas backup? Probably so, but expensive... might be the best of both worlds, though.
The only efficiency rating consumers ever get for their gas furnace is it's AFUE (Annual Fuel Utilization Efficiency). This number, expressed as a percentage, does not include the electrical energy the furnace will use to run the blower motor (in the case of a force air furnace) or the circulation pump (in the case of a radiant floor type system). The electric power to run these motors / pumps is not trivial. Eric has a good point regarding heat pumps, which this spreadsheet does not provide for. In the case of heat pumps, when you use the HSPF (Heating Season Performance Factor)which is also expressed as a percentage number, it includes everything, the compressor, supplemental heater(s) and the blower motor.
I think you need to specify whether you're talking about resistive heating or a heat pump ... a heat pump is much more efficient, if it works in your climate (air-source, or ground-source...) You can more 1W of heat into your house with less than 1W of energy, with a heat pump ... Thinking about a no-carbon future, electric heating has to be in the mix, but we have to do it efficiently....
Heating fuel costs are going up at the moment in europe (think in USA as well), so ditching the central heating and heating only the occupied room can make a positive change in energy bill amount. I recommend using radiant heater as spot or zone heater for a badly insulated space, but if your home is well insulated an oil-filled radiator with thermostat enabled would be the most energy efficient option. If you aren't able to decide, here are two articles which could shed some light on the pros and cons of different heater types: <a href="" rel="nofollow">comparison of convection heaters (oil radiators) and radiant heaters (infrared heaters, ceramic heaters)</a> and <a href="" rel="nofollow">comparison of gas heating vs electric heatring, pros and cons</a>

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