By using standard 2Watt Polycrystalline cells, available on sites like eBay, you'll enable yourself to build a 100 Watt panel for around $125. Some people even opt for chipped, or B-Grade cells, that produce the same amount of power but are defective by the manufacturer's standards (ie chipped corners, etc). With this choice of solar cells a completed 100 Watt panel may cost less than $70.
The Truth About Solar Panels: The Book That Solar Manufacturers, Vendors, Installers And DIY Scammers Don't Want You To Read - http://www.the-solar-shop.com/the-truth-about-solar-panels-the-book-that-solar-manufacturers-vendors-installers-and-diy-scammers-dont-want-you-to-read-2/
Hydronic radiant floor heating systems use solar energy collected from a homes pre-existing solar panels to heat water and send it through tubes laid beneath the floor. This hydronic system, used in conjunction with a solar water heater by SunEarth, is compatible with any type of floor.