Decarbonized power: how much wind and solar fit the optimal grid?

What should future power grids look like? Our 24-page note optimizes cost, resiliency and CO2, using a Monte Carlo model. Renewables should not surpass 45-50%. By this point, over 70% of new wind and solar will fail to dispatch, while incentive prices will have trebled. Batteries help little. They raise power prices by a further 2-5x to accommodate just 3-15% more renewables. The lowest-cost, zero-carbon power grid, we find, comprises c25% renewables, c25% nuclear and c50% decarbonized gas, with an incentive price of 9c/kWh.


Pages 2-4 illustrate the volatility of wind and solar generation at today’s grid penetration, providing rules of thumb around intermittency.

Pages 5-6 illustrate the strange consequences once renewables surpass 25% of the grid, including curtailment, negative power pricing and financing difficulties.

Pages 7-9 quantify and explain how much curtailment will take place in a typical grid as renewables scale from 25% to 40%, 50% and 60% of gross generation, using a Monte Carlo approach. The model shows when and why curtailment is occurring.

Pages 10-20 quantify and explain the costs of batteries, to backstop renewables as they scale from 25%, to 40%, 50% and 60% of the grid, while avoiding curtailment. Real world conditions are not conducive to competitive battery economics.

Pages 21-23 quantify the residual reliance on natural gas. Amazingly, even our most aggressive battery scenarios only permit 10% of gas-power capacity to be shuttered. Low-utilization gas is costly. High-utilization gas is less costly. And the economics of decarbonized gas are superior to any renewables plus batteries combination.

Page 24 concludes that natural gas will emerge as the ‘best battery’ to backstop renewables, estimating the most likely shares in an optimal power mix.