Myth #4 Natural Gas is clean and green

This myth is based on some old information and really good marketing by the Natural Gas industry.

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 # 2, that is no longer true as coal plants are retiring because they are not profitable and renewables have increased - so our electricity supply has become cleaner.

Many people think that natural gas is clean, but this could not be farther from the truth. In fact, burning natural gas for heat accounts for roughly one third of the total US carbon emissions annually. This includes the methane that leaks through the environmentally catastrophic process of extracting the gas from the earth. Fracking has led to even greater leakage of methane. That clean blue flame in the ads distorts the truth about this dangerous source of green house gasses.

The other incorrect assumption behind this myth is that we are comparing the emissions from natural gas heating to electric resistance heating. Electric resistance heating is how a toaster works, and until recently they were the only form of electric heating available. This method takes a lot of electricity which means that the emissions at the electric generation plant to supply that electricity are quite significant. But now electric heat pump furnaces and water heaters use 3 - 5 times less electricity than resistance heating. They are so efficient, they require much less energy to heat your home or your water.

Finally, if you are using 100% renewable energy to power your heat pump furnace or water heater - there are zero emissions created. It is not possible to burn natural gas with zero emissions.

Lets do the math for those who are interested (this gets a little geeky)

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

Resources: 

Energy Star product information https://www.energystar.gov/productfinder/

EPA  greenhouse gas calculations https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references

EPA carbon intensity of states electricity supply https://www.epa.gov/sites/production/files/2018-02/documents/egrid2016_summarytables.pdf