Floor Heating in Japan

We live in Nara & plan to get floor heating for our house. It's a major installation & we don't want to make a mistake. We are unsure which system is best, electric or gas-pumped hot water?

It'd be great if you could tell us your monthly cost as well as your installation cost if you have either one of these floor heating systems.

Thanks in advance.

Edit: The consensus says underfloor water pipes are the way to go. Right now, I'm leaning on getting a rooftop solar hot water system, boosted by an electric heat pump. With solar electric panels to create free daytime power, this might let me live my dream of having free interior heating!

All ideas appreciated. Thanks everyone for contributing.

by Exotic-Helicopter474