I hate radiators in kitchens and so I want to install an electric underfloor heating system. The floor is wood planks with with supporting joists.

I think you will be dissapointed with the amount of heat generated if you put half inch tiles over the top..... We have laid many underfloor heating systems and even with normal ceramic tiles the heat isnt fantastic. Also something that I always mention to my clients before we install underfloor heating is that if it goes wrong you have to rip up the floor...... in 10 years I have had to do this maybe 4 times so it is rare but it does happen. I would invest in designer radiators that are above the surface this way they still look nice and if you ever have any problems you can get to it without destroying your kitchen. We have installed radiators before that do not even look like radiators..... I think the best one was an upright semi circle fan rad and we put a lamp holder behind it with red lighting in and turned the radiator into a fancy light. I hope this helps

The electric systems actually work very well if the right system is selected in the first place, you MUST fit insulation beneath the system though or you will lose most of the heat downwards and not into the room. On the subject of the heating not working with half inch tiles that is rubbish! It actually works better as the thicker tiles absorb the heat and then release slowly and more evenly!