Myth #3 Heating with electricity is worse than heating with gas

This myth is based on two incorrect assumptions.  It assumes that the source of energy for electricity is largely coal and that the electric heating technology being used is old fashioned resistance heating.  We will see below that even the resistance heating technology using clean energy is still less carbon intensive than natural gas, and with modern electric heat pumps it is substantially cleaner.

It used to be true that heating with electricity was worse than heating with gas because most of the electricity we were using was coal fired.  As we saw in Myth # 1, that is no longer true as natural gas and renewables have increased and coal plants have retired and our electricity supply has become cleaner.

Until fairly recently, heating devices were using electrical resistance to provide the heat energy.  This is how a toaster works.  Whenever proponents of natural gas talk about how much cheaper and greener it is to heat with gas, they are comparing natural gas to old fashioned electric resistance heating.  Modern electric heat pumps used for water heaters and furnaces are 3 to 5 times more efficient than resistance heating.  This means they use 3 to 5 times less energy to heat your water or your home.  With this comparison, electric heating is cheaper and creates far fewer emissions.  Furthermore, if you are using renewable energy to power your electric heat pump, it is a zero emissions source of heat.

Lets do the math for those who are interested.

The easiest way to compare the 3 technologies - natural gas, electric resistance heat and electric heat pumps is to look at water heaters which are available in all three types.  The US Department of Energy provides very good information on nearly all available models through the Energy Star website and with the Energy Guide labels that are required on all water heaters.  All the information below is from those sources for 50 gallon water heaters.

The very best natural gas water heater has an efficiency of 0.89 and consumes 182 therms of natural gas per year to meet the Energy Star standardized test for hot water production.  According to the EPA, each therm of natural gas releases 11.68 pounds of CO2 when it is burned.

182 therms x 11.68 lbs CO2/therm = 2,126 lbs of CO2 per year

The best electric resistance water heaters have an efficiency of .93 and consume 3,493 kWh of electricity per year to deliver the required test amount of hot water.  According to the EPA, In Oregon 0.651 lbs of CO2 are emitted for every kWh of electricity produced on average.

3,493 kWh x 0.651 lbs CO2/kWh = 2,274 lbs of CO2/year.

So in Oregon where the grid is fairly clean, even a resistance water heater is nearly the same as the very best natural gas model.  This would not be true in other parts of the country where the grid is not as clean however.  The US average lbs CO2/kWh is 0.998 and in the worst regions of the grid it is as high as 1.668 lbs CO2/kWh - almost three times worse than Oregon which would make a resistance water heater in those areas much worse than a natural gas unit.

The exciting development however is electric heat pump water heaters or sometimes called hybrid electric water heaters.  Because of the amazing efficiency of heat pump technology, they have a rated efficiency of anywhere from 2.0 to 3.7 with models available today.  That means they are as much as 4 times more efficient than a typical electric resistance unit.

The best hybrid electric unit has an efficiency of 3.7 and consumes 1,255 kWh/year.

1,255 kWh/year x 0.651 lbs CO2/kWh = 817 lbs of CO2/year

That is over 60% fewer emissions per year than the best natural gas model!

Even an average hybrid unit will massively outperform natural gas.  A n average unit has an efficiency of 2.37 and consumes 1,906 kWh per year in the Energy Star test.

1,906 kWh/year x 0.651 lbs CO2/kWh = 1,204 lbs of CO2/year

So even an average electric heat pump model produces around 50% fewer emissions than the very best natural gas units.

Finally - keep in mind that all these calculations are using the carbon values for the average electricity supply in Oregon.  If you are using 100% renewable energy such as the Green Source plan, then it is legitimate to say that an electric water heater creates zero emissions.  It is still much better to use a heat pump model because it consumes so much less energy and that will also save you money each year.


50 Gallon Water Heaters Comparison - Oregon

Best Electric Heat Pump 817 lbs CO2 (Zero CO2 with Green Source plan)

Average Electric Heat Pump 1,204 lbs CO2 (Zero CO2 with Green Source plan)

Best Natural Gas  2,126 lbs CO2

Best Resistance Electric 2,274 lbs CO2 (Zero CO2 with Green Source plan)

Average Natural Gas 2,733 lbs CO2


Energy Star product information

EPA  greenhouse gas calculations

EPA carbon intensity of states electricity supply