Krugman: "But it is, I think, a useful corrective to the rigorous-sounding but actually silly notion that you can’t produce more without using more energy."
Of course you can produce more while using less energy. That is what has been happening throughout history. That is the wrong question, though. The problem has to do with maintaining employment while reducing the absolute amount of energy used. Producing more with less energy doesn't solve that problem.
UPDATE: Krugman proved Mark Buchanan right: economists ARE blind to the limits of growth!