While most of the press about radiant heat has focused on hydronics, makers of electric cable systems also report a healthy growth in their business. Electric radiant floors aren't appropriate for every home, but they can be an excellent solution for most design problems. Choosing the right system means knowing what you want it to do, and looking past manufacturers' claims to the system's real costs and benefits. Here are some guidelines.A big advantage of hydronic systems is the flexibility of the fuel source. You can use gas, oil, electricity and even solar energy. Plus, you can change fuels for the price of a new boiler. With electric cables, you'll save the cost of a boiler, but you can't change fuel sources. Special heating or off-peak rates available in some areas can make electricity equivalent to, or even less expensive than, fossil fuels.Another factor affecting cost is the size of the installation. Hydronic systems have high start-up costs because you have to buy a boiler. The installed cost of an electric floor can more or less be figured by the square foot. As a result, electric radiant heat tends to be more cost-effective on small floors. The larger the area you need to heat, the better a hydronic system will look. For instance, in a home with forced-air heating, it would probably cost too much to run hydronic tubes into a small bathroom. In this case, an electric floor-heating system would make much more sense.You should expect to spend $300 to $400 to install an electric system for warming a small bathroom. An equivalent hydronic system would run $4,000 to $5,000. Floor-warming systems can operate on less than 10 cents a day in a bathroom if electricity costs around 6 cents per kilowatt hour.