Speed Walking does not consume more energy than running!
I was referring to some of the times on this page:
http://www.racewalk.com/Results/MensRecords.asp
Where someone racewalked a mile in 5:38.2. Those dudes are fit.
Walking at 10 miles/hour takes more energy than running 10 miles/hour. But not more energy than running 15-18 miles/hour.
Now if speedwalking is different than racewalking then I guess you're right.