Costs and Emissions for My Electric Home

Back in late 2013, my natural gas furnace and air conditioner broke down beyond repair and needed to be replaced.  A decision had to be made: replace them with a traditional natural gas furnace and air conditioner or replace them with an air source heat pump with electric heat strip back up.  Since I live North of Chicago in a 2600 sq. ft home, I was advised against going all electric. I was told that I would freeze or that my costs would go up substantially.  Also, I was told that electric heating was worse for the environment.  The research I had done showed otherwise on these points, so, I opted for going all electric and getting off the natural gas grid.  (See previous article for new system details). At the same time, I traded in my Toyota Corolla for a Chevy Volt.

There was a learning curve in using the new equipment.  The Volt, for example, will turn on the gasoline engine at one of two temperatures to assist with heating the interior of the car.  The higher setting, at 35 degrees, uses more gas than the lower setting, at 15 degrees.  The default is 35.  It was several months into the first winter before I realized that the setting existed – the controls on the Volt are a lot more complicated than on the Corolla.  Setting the heating assist temperature to 15 cut my gasoline use substantially.

With regard to the heat pump, there are also many controls which effect the amount of energy used.  As with the Chevy Volt, it took some time to understand the optimal settings for the unit.  Additionally, I was not aware that, as an all electric customer, I was eligible for a electric space heating delivery charge discount of $.0125/kwh from my electric company.  It was not until recently that I could get an accurate comparison of annual costs and emissions of the old system vs. the new system.

Below is a table showing the costs and emissions associated with three different approaches. Scenario one assumes all traditional gas appliances and a Toyota Corolla driven about 10,000 miles.  Scenario two is the same house but with a Chevy Volt, also driven about 10,000 miles.  The last column shows my actual results for an all electric house (there is NO gas connection!) and a Chevy Volt driven about 10,000 miles.  In all three cases the house is assumed to be kept at 72 degrees year round with no additional heating sources and two occupants, including a teenager with friends over regularly.

Year Ending 9/16/2016 Gas Furnace
and Toyota
Corolla
Gas Furnace
and Chevy
Volt
Electric
Heat Pump
With Chevy
Volt
Cost $2,070 $1,636 $1,527
Emissions:
Current Grid
21,416 lb. 18,923 lb. 18,367 lb.
Emissions:
Renewable Grid
17,078 lb. 10,631 lb. 745 lb.

The costs and emissions for the Gas Furnace systems assumed 845 therms spread throughout the year based on my previous use patterns and heating degree days for my zip code (60030) as provided by weatherdatadepot.com. Costs were derived from rates provided by Northshoregasdelivery.com. Costs for the electricity included under the traditional columns is my previous estimated cost of $489 for the year.  For those two columns, emission calculations assumed 4500 kilowatt hours of electricity per year.  Emissions per therm are a standard rate of 11.7 lb. per therm. Electricity CO2 emissions are 0.964 lb./kWh as stated in ComEd’s Environmental Disclosure Statement for March 31, 2016.

The Corolla was assumed to use 367 gallons of gasoline. CO2 emissions per gallon of gasoline is assumed 19.6 lb. per gallon and average cost of $2.20 per gallon was assumed.  The gasoline use of the Chevy Volt for the year was based on an actual expense of $99 with an average cost of $2.20 per gallon. Energy used for charging the Volt was about 4100 kWh for the year.

Costs and emissions shown in the last column were from actual bills with electricity use of 18,284 kilowatt hours.  Because I use ComEd’s Real Time Pricing, I purchase my electricity at very low wholesale rates.  With this program my gross rate, that is after taxes, customer fees and delivery, is about $.08/kWh. The costs shown do not include renewable energy certificates which effectively drop the emissions to zero. Voluntary wind renewable energy certificates are currently about $.02 per kilowatt hour.  For my electricity use this would equal about $360 and would effectively make my electricity emission free.

The primary reason converting to an all electric system is that as more zero carbon energy sources added to our grid, the closer our grid will get to being 100% renewable and emission free. The emissions listed in the far right column for an assumed renewable grid are only 745 lb whereas, even with a 100% renewable grid, staying on the natural gas grid leaves me with an unacceptable CO2 emissions of 10,631 lb.  We cannot make the natural gas grid emission free.  Our electric grid, however, is getting better.  Both solar and wind are getting less expensive as is storage technology.  By using an all electric system today,  my emissions are lower as are my costs. As time goes on our electric grid will move in the direction of an all renewable grid.  Things are getting better!