"<a href=""http://www.youtube.com/watch?v=XS36ijvZOME&amp;t=1m10s"">1:10</a> Nuclear", coal, gas, much harder start up.<br><br>Uh, no.  Gas turbines are very easy to start up and shut down.   The other two I'll grant.,(reply>), @ codediporpal :  No, these are not "gas turbines"; they're <b><i>steam</i></b> turbines powered by boilers heated with natural gas.   So they take a while to heat up before they can be brought online.,(reply>), It's not even so much startup or shutdown, it's the speed at which the amount of power being generated can be varied, and the generator taken from being disconnected but idling the turbine at near-grid-speed (using only a smidge of fuel and steam because there's no load on it) to connected up and running at full speed and full bore. As your working fluid is water steam, and even with a massive gas burner it takes a minute or to superheat the fluid within the system from its barely-boiling starting temperature, and several more to bring the thing up from cold and stationary, you need something a little more agile, if overall lower powered and less reliable, to plug the gaps whilst it comes back online.<br><br>Also, I'd expect nuclear and oil-fired to be almost as quick to react as gas. It's coal and biomass generators that take a particularly long time to stoke as you can't just inject more fuel or expose more of the rods and get a near-instant boost to the flames or radiant heat boiling the water, but actually have to pile more material onto the furnace grate and wait for them to catch and the fire to grow... Which is probably just one good reason why the main thing that renewables are displacing is coal. Biomass is at least no worse than coal in terms of reaction time but is carbon neutral and has cleaner emissions, and everything else is much faster to respond when connected or disconnected and are essentially zero emission and negative net carbon.