Wednesday, June 2, 2010

Calculating Personal Energy Use

Recent events in the Gulf of Mexico have reminded me that producing, transporting, and using energy has many obvious and hidden costs, including the potential for catastrophic environmental costs.  To make informed decisions about potential changes in energy use as individuals and as a nation, it is useful to begin by calculating energy uses.  If wildness and the ecological services that we receive are to be conserved, part of this effort requires a better understanding of energy uses.  
I have prepared an example using our home on Beaver Creek marsh.  We use propane for space and hot water heating, cooking, and refrigeration; gasoline for a backup generator; douglas fir for firewood; and solar electricity.   Energy comes in various forms and making comparisons requires having common units.  I have converted types of energy we use to Mbtu (million btu; British thermal units) for comparisons.  Jackie and I built and live in a house that has 1248 square feet of space.  In a year for the house, we use: 
400 gal propane      =  36.64 Mbtu
120 gal gasoline      =  13.80 Mbtu                                       
3 cord firewood        =  72.00 Mbtu
550 Kwh electricity   =    1.87 Mbtu 
Total residential        =  124.31 Mbtu
(Assumed that 1 gal propane = 0.0916 Mbtu; 1 gal gasoline = 0.1150 Mbtu; 1 cord fir wood = 24 Mbtu; and 1 Kwh electricity = 0.0034 Mbtu).
How do these numbers compare with average use?  In Oregon, total annual energy use per capita = 297 Mbtu.  This total is derived by adding up total energy used in the state and then dividing by the number of people.  The total includes residential (24.2%), transportation (31.3%), commercial (18.9%), and industrial (25.6%) sectors in the state.  So the average annual per capita residential use in Oregon is 71.87 Mbtu and for two people is 143.74 Mbtu.  Jackie and I use 124.31 Mbtu, or approximately 86.5% of the Oregon average.
This is a simplified picture of our residential energy use.  We have not included the energy required to produce and transport the propane, gasoline, firewood, and electricity that we use.  We could assume that those btu were included in the other sectors for per capita energy use.  But these fuels are not all produced in Oregon, so that assumption is not valid.  Dividing up energy use by state borders is an arbitrary comparison that does not match our purpose.  We need to expand our data base to include much more information that is beyond the scope of this post. 
We have not included the energy for building, furnishing, and maintaining the house and its appliances.  That energy derives from both economic and ecological sources and may be considered in more complex life cycle calculations.  Other personal life cycle energy uses include energy for producing, transporting, and marketing our food, clothes, entertainment, education, and car.  
How about fuel for personal transportation?  We have one car and use 480 gal gasoline per year, or 240 gal per capita.  The average per capita use of car gasoline in Oregon is 434 gal.  So we use 55.3% of the average.     
So Jackie and I use less energy in our residence and car than average.  We assume that less energy use is better for the world and may be able to reduce our uses without reducing quality of life.  To begin we can make an audit of our residential uses and potentially improve the efficiency of energy uses, i.e., get more out of each btu and use fewer btu.  We can begin to consider the life cycle energy for our food, clothing, entertainment, and transportation.  Too complicated?  It is no wonder that many people simply want to go into a room and turn on a light switch, saying “don’t bother me with these details”.  They usually forget to turn off the light when they leave the room.  “The lights are on but nobody is home”.
Posted by michael  

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