Electric Heat – Thermal Efficiency Disaster, part 1

For a long time, I have been wanting to do a post about the disaster that is electric home heating produced by coal-fired electric power plants.  Today, Pam Kasey over at Grounded gave me the opening I was looking for.  Her article about AEP’s electric efficiency programs includes the following paragraph about why WV residential electric bills are so high:

One reason may be older, less well insulated housing stock. In addition, a much higher share of Appalachian Power and Wheeling Power customers heat with electricity: nearly 49 percent, according to information shared by customers when they signed up for service, compared with 29 percent among FirstEnergy West Virginia customers in 2009.

According to power companies’ best estimates, 49% of AEP’s WV customers and 29% of FirstEnergy’s WV customers heat with electricity.

Every time you run a heating element, whether it is in your furnace, on your stove top or in your water heater, you are turning on the most energy intensive equipment in your home.  As anyone with an electric furnace or portable heater knows, heating is the biggest part of your electric bill.

In WV, we often hear that coal is the “cheapest” source of energy in our state.  While that may be true for the fuel itself in terms of BTU output, we also have to take into account other costs of turning that coal into useful energy in our homes.  When we start doing those calculations, coal’s costs rise dramatically.  Coal’s comparatively poor overall efficiency in the electrical heating process is the reason.

When coal is burned to run a steam turbine in the average coal fired power plant, only about 33% of the coal that is burned actually ends up as the power that flows out of the plant.  The most advanced coal fired power plants can run at 42% efficiency, but there are not a lot of them.  These ratings are referred to as thermal efficiency, because they are measures of the conversion of heat to the form of energy that is produced, in this case electricity.

To get to your house, that electricity has to flow through bulk transmission lines and substations and through distribution lines to your main breaker box.  In that process, the system, on average, loses about 7% of the electricity that left the power station.  That is referred to as line loss.  Deducting 7% of 33% (thermal efficiency of the coal plant), that leaves us with a thermal efficiency of 31%.

But that’s not all.  In order to turn that electric energy at your house back into heat again, you have to run it through an electric furnace.  An electric furnace is actually pretty good at keeping all of the electric energy that it takes in into home heating.  That is mainly because the electric heating element does not require exhaust or ventilation, so that all the heat it generates stays in the home.  The US DoE’s home heating calculator rates electric furnaces at 100% efficiency.

Multiplying the thermal efficiency of the coal fired electricity coming into the home by the 100% thermal efficiency of the electric furnace, we end up with an overall thermal efficiency for electric heat of 31%.

Now let’s look at the other main heat alternative available to most West Virginians, natural gas.  With natural gas, the combustion of fuel takes place right in the home furnace.  This makes a lot of sense, because, after all, we are talking about home heating.  If the burning of fuel takes place right where it is needed, the whole process is quite likely to be very efficient in terms of its conversion of heat to home heating.

Because we don’t have to calculate the efficiency of burning fuel to produce electricity or how much electricity is lost in transmission and distribution, the only efficiency that matters in calculating the thermal efficiency of gas heat is the efficiency of the home furnace itself.  The DoE calculator lists the thermal efficiency of a gas furnace at 82%.  It is less efficient than the electric furnace, because combustion gases are vented outside the home, and 18% of the combustion heat is lost in that exhaust.

In our home, we use a combination of unvented gas space heaters and high efficiency wood stoves for heating.  The DoE lists the thermal efficiency of unvented gas space heaters at 100%, because all combustion heat remains in the home.

So with gas heat, 82% of BTUs produced by burning the gas is converted directly to home heat.  With electric heat, only 31% of the heat from burning coal ends up as heat in your home.  Why did West Virginians end up with such an inefficient and wasteful system of heating their homes?

According to Phillip Schewe, in his great book The Grid, there is a good reason for it.  Back in the early 20th century, electricity was still pretty expensive.  Some power company managers realized that if they built huge new generating plants, they could actually sell electricity more cheaply, if they could sell enough electricity to pay for these new power plants.  If they could get enough customers, buying enough electricity from these big regional plants, the economics of scale from these larger plants would mean everyone’s rates per kilowatthour would fall.  Everyone’s electric bills might go up, because they were using more, but the new electrical uses, like heat, would be cheaper than a lot of competing heating sources.

Schewe recounts the story of how Commonwealth Edison gave away free electric clothes irons if people signed up for electric service.  Irons replaced a very dangerous and time consuming task of heating irons on coal and wood stoves, and, at the same time, generated a lot of new electrical use, because they used heating elements.  Encouraging home heating with electricity, for a while, actually contributed to falling rates, as long as power plant costs and fuel costs (mainly coal) were relatively low.

We no longer live in that transitional era.  Demand for electricity is now flat in the US.  Construction of new coal fired plants is now expensive and risky.  Coal is now a relatively expensive fuel.

So we are back to the question of the efficiency of our electrical system.  I would argue that we cannot look at efficiency in isolation from all forms of energy production.  Increasing the efficiency of electric heating, in the home, is not possible anyway, because the thermal efficiency of electric furnaces is already 100%.  Increasing home sealing and insulation is not really a thermal efficiency measure, because it does not increase the efficiency of the heating process.  Insulation and caulking are thermal conservation measures, because they reduce the amount of thermal energy needed to heat the same space.  These conservation measures do shave costs, but not on the scale of shifting heating from one technology to another.

The only way to increase the thermal efficiency of home heating is to shift home heating from electricity to gas heating or some other form of heat that is more thermally efficient than electricity’s dismal 31%.  The fact that almost half of AEP’s WV customers and almost a third of FirstEnergy’s customers heat with electricity shows that there is a huge opportunity here to dramatically increase WV’s home heating efficiency.

Of course, we also have the issue of fuel cost.  Gas is also very cheap now in WV, far cheaper than coal.  Even the most efficient gas fired power plants only have a thermal efficiency of about 60%.  Why burn that gas hundreds of miles away in an electric plant, and lose 7% of it to line losses, when you can burn that gas in your own home and benefit directly?  And all that gas delivery infrastructure is underground, unlike the power companies’ lines that are constantly going down, shutting down your furnace completely.

This post is long enough.  I will deal with some larger questions in my next post.

2 thoughts on “Electric Heat – Thermal Efficiency Disaster, part 1

  1. Just a thought. For the last few years, I abandoned oil heated baseboard hot water for heat. I use electric heaters, heating only the room I am using at a given time. I have insulated by pipes, and use my grandmother,s antique wood fired kitchen range to heat the basement. The wood comes from storm timber from the last few years and the Derechio (spelling). My last electric bills from November to now have been $134.00 and $101.00. Oil for the same period would have cost me over $3000 for the same period. LP gas would have been as bad. I switched from and LP gas range to an electric range, and this will eliminate a $400 per year propane (LP) bill. When economics allow, I will switch to a geothermal with an indoor heat pump, supplemented by solar panels and a windmill. That is if Jefferson County zoning doesn’t take the position of POTOMAC EDISON and rule me in violation of the height restriction. I know I can reduce my carbon footprint more yet, but that must wait until it is affordable. One must have income in order to take advantage of tax credits. Finally, I have an antique UNITED STATES SYSTEMS 500 KvA generator, powered by an in line flat head 6 cylinder Hercules natural gas engine and the disconnect switch. (Yes, that is KILOVOLT AMPERES!!!!) Does anybody have any suggestions about how to restore this antique to operating condition? It is a circa 1930 unit, which my father bought from VEPCO’s Mount Storm, WV facility in 1972. Sorry if this is TMI. Danny Lutz p.lutz007@gmail.com

    • Danny,

      One thing is certain, you are no longer thinking like a consumer. Wow. If you get that natural gas generator fired up, you could use it on a local microgrid with your neighbors.

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