We present a model of growth driven by energy use and endogenous factor-augmenting technological change. Both the rate and direction of technological progress are endogenous. The model captures four main stylised facts: total energy use has increased; energy use per hour worked increased slightly; energy efficiency has improved; and the value share of energy in GDP has steadily fallen. We study how energy conservation policies affect growth over time and in the long run. Policies that reduce the level of energy use are distinguished from those that reduce the growth rate of energy inputs. Although these policies may stimulate innovation, they unambiguously depress output levels. The former policy has no impact on long-run growth; the latter reduces long-run growth both in the short run and in the long run.