That's implying that technology won't improve. You are ignoring renewable energy such as sun, wind, geothermal, etc. and nuclear energy (and nuclear fusion).
According to everything I've read all the renewable energy sources we have combined cannot solve the problem to supply the amount of energy needed, nuclear fission very unpopular (so not likely to get greatly expanded) and nuclear fusion has yet to produce more energy than has been spent on trying to achieve it (perhaps if we get *lucky* that might change).
We've been talking about this problem for years though. Technology allows production to increase and usage to drop as products become more efficient. Additionally, population growth is finally slowing down.
If a real energy shortage occurs, people will just have to get over their objections to nuclear fission. And we're currently burning off natural gas instead of using it for electricity. We aren't anywhere close to using the earth's entire energy capacity.