Generally, solar hot water will give you more "bang for the buck."
- PV is 12-22% efficient and expensive compared to solar hot water, which is 60+% efficient.
- If the budget allows, both are great.
My favorite saying is "reduce then produce".
- First look at ways to reduce you utility bills by upgrading the efficiency of you home: insulation, air sealing leaks, fixing leaky ducts if you have forced air heat, etc.
- A great website to find all about this stuff is buildingscience.com.
For more information:
Read "Can you tell me how well solar hot-water heaters work?" a Q&A answered by Paul Rosen.