5. Non-Renewable: As of today, fossil fuels are being extracted at an exorbitant rate to meet the gap between demand and supply and it is estimated that they will be finished in next 30-40 years. Since they are non-renewable, it is more likely that fuel expenses will face a steep hike in near future. It would take millions of years to replace coal, and oil, and this means that we will not be able drive cars anymore unless we switch to electric cars that use energy from renewable energy sources. This means once these non-renewable sources are completely used up, there is nothing more left.