When building or buying a solar hot water system, keep these things in mind:

1. Be sure to include a freeze valve on your system. A freeze valve will keep your system from freezing solid and cracking. These valves often sense when the water temperature is about to dip below freezing and bleed enough water out of the system to circulate relatively warm fresh water. These are a must-have for passive systems.

2. Install a shut-off, bypass, and drain spigot on your system. These valves allow you to detach the solar hot water collector without completely disconnecting the water to your existing hot water tank. They can come in very handy, especially if your system does not have a freeze-prevention valve.

3. Install scald guards on your system if you live in a sunny climate. Solar water heaters work at times work so well they can present a scalding danger to the home's occupants.

4. Rebates abound! And many states now offer additional rebates. In some cases, these can almost completely offset the purchase price of the system, which allows for an even faster return on investment. Find out if rebates are available in your state.