Four years after the earthquake and nuclear plant meltdown, Japan has gone cold turkey on nuclear energy. For now, zero reactors are currently in operation.

Solar energy has sought to fill some of that void. Thanks to subsidies and affordable, efficient solar panels, Japan’s solar market has grown tenfold in the last two years. Then, utilities controlling the grid pushed back, and refused to take additional solar energy.

There are technical trade-offs, says engineering professor Massoud Amin at the University of Minnesota, that can cause brownouts and blackouts.

There are fixes, a complex assortment of solutions often referred to as a smart grid. But that requires an enormous investment, that Paul Scalise of the University of Duisberg-Essen in Germany says raises a fundamental question: Who pays for it?

This is a clean-energy issue that doesn’t just face Japan. Germany, Spain, Australia and California all confront questions of grid reliability and upgrade. While it may be in the interests of some utilities to resist change — and hold off direct competitors in the power generation space — inaction in the case of Japan comes with its own trade-off: the environment. Without nuclear energy, the country increasingly relies on imported fossil fuels.