... extra cost after installation6.Design for you, OEM available, The type you can choose : 15, 18, 20, 24, 30 ... need waiting. Compare Solar to Conventional Water Heater SOLAR WATER HEATER: FREE energy from the SunSTANDARD WATER HEATER:COSTLY gas or electricAnnual operating cost: almost freeAnnual ... (the sun's energy) will always be free. solar water heater/non-perssurized best sell energy system with CE