Digits for the U.S....i.e. not hundreds of years like in the Middle East or Venezuela...so long as we rely on Fossil Fuels, we are at the mercy of those with the biggest stockpiles...we MUST substitute Oil usage for Heat and Power...fortunately, we have a nuclear program that can extend uranium 'reserves' in our already "Spent Fuel" to supply planned reactors for more than a hundred years, some reports say thousands of years. Then there are Renewables for uses where "Dispatched Energy" is not an issue...
Let's get moving...and stop fighting the inevitable.