  The effects of the spatial scale on the results of the optimisation of
transmission and generation capacity in Europe are quantified under a 95% CO2
reduction compared to 1990 levels, interpolating between one-node-per-country
solutions and many-nodes-per-country. The trade-offs that come with higher
spatial detail between better exposure of transmission bottlenecks,
exploitation of sites with good renewable resources (particularly wind power)
and computational limitations are discussed. It is shown that solutions with no
grid expansion beyond today's capacities are only around 20% more expensive
than with cost-optimal grid expansion.
