The same review also shows that under these and even less ambitious renewable energy scenarios, it is expected that a global share of more than 5 per cent of intermittent modern renewable power will be reached by 2020. This will require some sort of smart grid to deal with load balancing, which in turn means that these scenario plans assume the rebuilding of the existing power grids in most large economies within the next 10 years, an extraordinarily ambitious undertaking (comparable undertakings in previous energy transitions took more than 50 years). In this scenario, demand for all types of energy increases in non-OECD countries, while in OECD, demand for coal and oil declines.