Oven preheat - solar?

Exiled_Tyke

I have a brand new oven which impresses me in that the door stays incredibly cool (to me at least) when the oven is hot.  I also have a pretty new microwave which has a convection oven included. I'm guessing this is far less insulated but also has to heat a far smaller volume of air.  Similar to my previous experiment (which I refer to far too often I know) where I found that a kettle on a gas hob was only 10% cheaper than using an electric kettle (so is now probably more expensive) I now feel I need some hard data on using my main oven, my convection in the microwave and I suppose the micro-wave combination function.  Any volunteers to do this for me?