How to calculate energy balance at pv- panel and water heater?

1. How to calculate solar energy balance of PV- panel and water heater ?
2. How many percent of irradiation turn into electricity and how many percent it reflect at the PV- panel and water heater?
3. what is Similarity and differences of Pv- panel and water Heater ?
Thx ! I really appreciate your help ! Thank You

Keefe Plumbing Company, Inc. provides the very best plumbing services with 24 hour emergency services in Chattanooga at the most affordable prices. Visit http://www.keefeplumbing.com/ or call 423-622-3178 now for more details.
http://www.keefeplumbing.com/