Gtoe is an abbreviation for "giga tonne oil equivalent", a common measure of global energy. A billion tonnes of oil contains roughly 10,034,000,000,000,000 Calories (kilocalories, as in the energy to heat one gram of water one degree Celsius, not calories as in the food measurement) or 4.1868E+10 gigajoules or 11,630,000 gigawatt-hours. As of 2003, the world uses roughly 9 Gtoes worth of energy per year, from all energy sources combined with an annual growth rate of roughly 3%.