China is one of the fastest-growing energy markets on the planet, with its demand surging at a 6.3% annual rate over the last 20 years. However, that growth rate will slow in those to come according to an outlook by BP (NYSE: BP). The oil giant estimates that Chinese energy demand will only increase at a 1.5% annual rate through 2040, though at that pace, it will consume a quarter of the world's energy by that year.While China has been the main driver of global energy demand growth in the recent past, BP sees India emerging as the fastest-growing energy consumer in decades to come, with its consumption expanding at a 4.2% annual rate, setting it up to explode 165% higher by 2040.