In Europe, grid-level costs for wind onshore represent about 20-65% of the total electricity generation cost for dispatchable technologies, while even higher values are observed for solar and wind offshore, on average, grid-level integration costs for renewables account for about 50% of the total electricity production cost.21 As an illustration of the relation between plant-level and grid-level system costs, Figure 4.9 shows the total costs for the six technologies in the United Kingdom. This analysis, however, does not fully account for other important aspects associated with the introduction of the new technology into the electricity system. The reference system is a mix of conventional dispatchable technology such as gas (CCGT), coal and nuclear based on the respective shares in the national energy mix. The "new” electricity system is constituted by variable renewable sources, at 10% or 30% penetration level, while the residual electrical load is covered by dispatchable technologies.