Which energy source will we run out of first, oil or hydropower?

Answer 1

Oil. Current reserves about 30 years + maybe 20 years of reserves yet to be tapped + about 50 years 'sand-oil' - oil mixed with sand which we've ignored so far because it's more costly to extract.

Hydropower is generated by water, as long as we've got water we'll have hydropower.

Answer 2

oil