In my view, the long-distance transmission of intermittent renewable electricity is not a cost-effective way to reduce emissions (J. A. Mathews and H. Tan Nature 513, 166–168; 2014). Power transmission is highly inefficient, with 3.5% or more being lost from an ultra-high-voltage line over 1,000 kilometres (see go.nature.com/dli4we).

China can produce renewables cheaply because of economies of scale, market expansion, low labour costs and minimal environmental regulation. But this may not be sustainable. Already, the availability of resources and competitive utilization are challenging.

Electricity demands vary in different regions, from low in the wind-rich north and west of the country, to high in coastal areas. The cost of transmitting electricity over such vast distances is unlikely to be offset by increasing wind-turbine operating hours.

The remote use of renewable electricity might be much more expensive per unit than electricity produced by conventional generators, even considering the social cost of carbon. In most cases, the costs will also be higher compared with locally generated renewable energy, even when those resources are limited.