The large-scale deployment of solar and wind generation has changed the paradigm of power systems and electricity markets in which prices were traditionally based on marginal generation cost and fuel prices. Most of generation capacity was considered dispatchable and available throughout most of the year. Solar and wind do not require fuel and have practically zero marginal generation costs, although they are available only when the sun shines or the wind blows. IRENA is at the forefront of the discussion on how to best plan and operate a power system with large shares of solar and wind, and also contributes to the global debate on electricity market design for renewables. Specific issues raised by Member countries have been timely addressed in specific guiding documents – such as that on grid codes for variable renewables – or by providing specific advice to Members on those issues.