Energy as a concept will never run out. Everything has some energy and we never actually destroy it, only change it into a different type of energy. However, the fossil fuels (oil, coal and gas) that we use to produce most of our electricity, fuel for cars and heating will run out. I’m not sure what the current estimate is as it changes a lot, but it might well be within your lifetime. Other energy we use comes from the sun. For example solar power and the energy that plants use to grow. Eventually the sun will also run out of energy, but that will be millions or billions of years in the future.