A number of people have set me straight on why it doesn't make any sense to heat water with a heater element connected to a PV array. Basically, it comes down to efficiency and ability. Essentially, it's too inefficient and slow, and not cost effective to heat water using PV arrays. Of course, it doesn't make sense to buy a PV array with the intention of heating water. However, if you already have solar modules, it might make perfect sense to use them for water heating.
Most people size their solar array for the lowest amount of sunshine during winter months.
Consequently, they have much more power than they need during the summer. Voltage regulators prevent batteries from over-charging during these times but also waste what could be considerable power. Q. I am interested in your solar panel for powering my IBM PC110. We don't recommend using diodes with solar modules this small - you lose more power during the day with a diode than you would lose at night without one. Q. I plan to move soon, and hope to build my dream home.