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The U.S. Energy Information Administration lists data from 2022, saying that of energy demand in this country, 37.6% were electric, 27.3% were for transportation, 23.1% were for industry, 7.1% were for residential use, and 4.9% were for commercial use (https://bit.ly/Energybreakdown).
If we electrify everything, the share coming from electricity would be increased from 37.6% to 100%. That might seem to imply that the amount of electricity we need would have to grow to 266% (100/37.6) of what it is now. This, however, is not the case.
We might consider a comparison of electric cars with those powered by gasoline. The U.S. Department of Energy says this about electric vehicles (EVs): “EVs convert over 77% of the electrical energy from the grid to power at the wheels. Conventional gasoline vehicles only convert about 12%–30% of the energy stored in gasoline to power at the wheels.” (https://bit.ly/DOEcarcompare)
A more complex, but more instructive example is comparing an oil-burning home heating system to one that centers on one or more heat pumps. If we look at gas furnaces, an 80% annual fuel utilization efficiency (AFUE) rating was considered good at one time. That meant that only 20% of the heat went up the chimney. Some newer furnaces have AFUEs of 95%. We could exclaim about that second figure because it is so close to 100%. And nothing is ever all the way to 100%, right?
An electric resistance heater is usually close to 100% efficient. That means that the heat energy created by a resistance heater is equal to the electric energy making it go. So, we can have something that could theoretically be 100% efficient. But clearly, nothing could be better than 100%, right?
Well, no. Efficiency and percent both must be considered carefully. In both cases, we really don’t know the meaning of the word, unless we know the meaning for this application, in this context. That means that in either case some explanation should be given.
An article in a recent edition of MIT Technology Review says, “Heat pumps’ real climate superpower is their efficiency. Heat pumps today can reach 300% to 400% efficiency or even higher, meaning they’re putting out three to four times as much energy in the form of heat as they’re using in electricity. For a space heater, the theoretical maximum would be 100% efficiency, and the best models today reach around 95% efficiency.” (https://bit.ly/MITheatpumps)
We should recognize that the word “efficient” is being used very unconventionally here, and the idea could possibly have been said better another way. It is really more accurate to say that a heat pump has a coefficient of performance (COP) that is 300% to 400%. That means the amount of heat energy delivered by a heat pump is three to four times as great as the electric energy used to power it.
We might do well to consider that. We can get three or four times as much energy from a heat pump as the amount of energy that goes in. That seems to violate the laws of physics about the conservation of energy and mass. But a close inspection of what is going on shows that the magic can be explained.
The magic arises because a heat pump does not normally create heat, which is what burning fuel or heating with a resistance heater does. Instead, it moves heat.
It is not really all that hard to envision this. Nearly all refrigerators have heat pumps in them. The heat pump in a refrigerator removes heat from the cold inside of the refrigerator, making it colder, and discharges it into living space, making the kitchen warmer. So, a heat pump appears to be far more efficient than oil furnace or resistance heaters because the heat pump moves heat instead of creating it.
That lengthy explanation illustrates (we hope) the fact that when we electrify things, we can be much more effective in doing the same work with less energy. That appears to be an increase in efficiency.
Putting electric vehicles on the road will mean that we use more electricity, certainly, than if we power them with combustion. But they will also change the demands for electricity at different times of day. This is because the EV will be charged at night, when demand for power is low, and will often be used as a battery resource when demand is high, in the afternoon or evening. So having more EVs could increase the amount of electricity used during a 24-hour period, but also reduce the peak demand. An article on the grid and EVs appears on page 8 of this issue of Green Energy Times.
As we move to electrifying things, we should do the overall work of becoming more efficient. When we install a heat pump, we should do the work of testing weatherization and insulation. If there is a need for improvement, as there often would be, the whole house becomes more efficient. In theory, we could find that a house is so efficient passively that heating it at all is not normally necessary.
In the course of the transition to zero emissions, we are likely to see sharp increases in the amount of consumer-produced electricity. Rooftop solar systems and passive houses could make local grids less dependent on imported energy. This would mean electrification could even reduce the overall use of energy. In theory, we could even come to use only electric energy, but use it so efficiently that the demand would decrease.
New transmission lines are replacing the old infrastructure all over the capital region of New York State. Shown are lines that cross New Scotland So. Rd, Delmar, NY. (N.R. Mallery)
Towers seen from rt. 20 east of Duanesburg, NY waiting to be errected as the state continues to improve the grid efficiency in the capitol region. (N. R. Mallery)