Energy Costs versus House Age

Modern homes are built in more energy efficient ways.   New homes usually have better insulation, more energy efficient double pain windows, more efficient furnaces or air conditioners and other energy efficient improvements over older houses.   It then only stands to reason that newer homes should be cheaper to heat and cool. 

Of course newer homes are often larger than older homes so some of that efficiency gets masked by the higher energy costs of a larger home.   Therefore the best way to compare the energy efficiency based on age and improved building practices is by the average cost per square foot.

I found information on average energy spending per homes from the US Energy Information Administration and they broke it down into the decade the home was built.   The numbers are from 2005 which is the most recent covering this information.

Here's the data :

Year of Construction	$ / sq ft
Before 1940	0.88
1940 to 1949	0.88
1950 to 1959	0.86
1960 to 1969	0.90
1970 to 1979	0.89
1980 to 1989	0.85
1990 to 1999	0.76
2000 to 2005	0.68

Interestingly there aren't t major differences in the amount spent on the homes from 1940 to 1979.   It seems that the biggest efficiency improvements kicked in after the 1980's. 

If you were looking at a home built in the 1960's versus one built after 2000 then you could expect to see about a 24% decrease in average energy expenditures.

I should point out that this analysis is not perfect since this is just the amount people spent and not necessarily an indication of the different quality of home building per decade.   In other words its feasible that people who own older homes are more likely to waste energy or something like that.   I haven't proven a cause - effect here.   Also the data doesn't take into account other variables such as who owns the homes, where they are built, etc.  Its also possible that more of the new homes are built in states with lower energy costs.   However I think its pretty reasonable to take national spending averages and then assume that the differences are related to building practices based on building age.  

It should also be noted that these are just national averages and individual spending will vary greatly in different climates and other factors.    

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