You used to be able to predict how much energy a home would use, just based on how big it was. Either heating or cooling took more energy to change the temperature of a larger space.
We can’t do that anymore. Homes increased in size from 1,800 square feet when built in the 1980s to 2,465 square feet when built in the 2000s (remember when we built houses?)
Not only did they get bigger, but the ceilings got higher as well, meaning there was more air to condition. Just 17% of homes built in the 1970s had ceilings higher than 8 feet, but 52% of homes built in the past decade did.
So what happened to energy consumption? It dropped–dramatically, from 127 million BTUs per household annually to 90 million.
It’s not because everybody moved back in with mom and dad, either. The largest segment of households had 2 people only.
What’s happening is that energy consumed per square foot has dropped as house size has grown. Small and older houses use a lot of energy–sometimes three times as much per square foot as larger, more modern houses.
Energy efficiency is being incorporated into new buildings and it is working. We’ve grown from 80 million houses to 117 million and are using the same amount of energy. We’ve grown from 226.5 million souls in 1980 to 308 million in 2009–and it isn’t taking any more energy to house us.
Good for us.
3000 Quads 
Many americans migrated to south states. Is 90 MBTU include electricity generation? If no, electricity generation consumption must be included also. Gasoline, jet fuel must be also included. The energy content of imported goods must be included also.
I think, more complete study of american household energy consumption needed.
Tom, I learned a couple of things from your blog so far. 1. Evidently, FOX and Common Dreams, etc. don’t post talking points on underestimates of future energy needs. So you are only getting real, thought out responses. 2. If we truly are underestimating future energy use, we could be backing into decisions which are every bit as dangerous as ones we think that we are making now.
I will eventually get around to a long post on an alternative route to development based on my recent experience living in the Chequmegnon Bay area of WI. I think what we see there is an information intensity replacing an energy intensity.
I’m spending a lot of time away from electronics lately and my health does seem to be improving.
Tom,
From my apparently endless supply of stories accumulated during a career in construction:
In 1979 I was designing a couple of houses to be spec-built in Boca Raton, Florida. Boca Raton had a new energy code which was expressed in a formula which I have forgotten. The effect of this formula was to insulate the daylights (appropriate term, as you will see) out of the house.
These were to be upscale homes and IIRC were about 2,700 square feet and constructed with wood-truss roofs and reinforced masonry (concrete block) walls.
Concrete block walls don’t insulate easily so I provided furred-in drywall with insulation on the interior, 1 foot of insulation above the ceiling, ran their formula on my trusty TI-59 (with the printer and the little magnetic cards) and hadn’t achieved the number they were looking for. So I triple-glazed the windows and added another 4 inches of insulation in the attic and brought the wall insulation up to 4 inches – still no joy.
The code required minimum window areas in the habitable rooms and I tried dropping the areas to half what was required – still, no joy.
Then I played with the formula and tried ridiculous numbers – with ridiculous amounts of insulation, I could get close to what was required, but still, no joy.
I called the building department. They affirmed that their formula was correct and yes, all of the plans they were approving had the numbers worked out and the designs complied.
So I got out the Yellow Pages and called another architect. I asked.
“We fudge the numbers. It really is impossible to meet this code, but if you triple glaze the windows, provide 3 inches of insulation in the walls and a foot in the attic, they will think you’ve complied with their G**damned formula.”
And incidentally, we just returned from our annual visit to civilisation (UK) where I drove a Peugeot 207 (turbo diesel) 1330 miles with 101 liters or 55 mpg. It’s true that a lot of this was in the Scottish highlands where my nerve wouldn’t support a speed greater than 50 mph, but…..
Car was not tiny.
http://www.dvorak.org/blog/2012/08/09/alternative-air-conditioner/