. >> this is made locally by hel helio dime. it's at rolls royce of flat plate water heating system. it has been a small business in richmond. they work with high quality materials. what occurs with this panel when they are usually much bigger when we have them on buildings. it's a sealed box it has copper piping the header and the rise or and the metal in between and we circulate water through it a gallon per minute per panel and we collect the heat during the day and this gets hot like your car would on a hot day of the it's a sealed box. it's a cell tifl simple concept. it does have a very fancy, for lack of a better term, surface or coating called black chrome a hi emitant coating so it retains the heat that gets to t. that's the basic model of a flat plate solar panel. >> how much do these rigs cost? >> this sample is simply a sample, of course. by can and large after tax probably per panel we are pushing with the price of copper, 8-900 dollars. >> how many panels people need to do one of these typical san francisco home? >