While buying solar gyser stick to good reputed companies like Tata, Racold, V gaurd etc.There are lot of small manufactures coming out of bangalore, its better to avoid them.
They are small fabricators who buy scrap from big manufactures at throw away prices and repair and sell it to you using flashy websites and hi fi showrooms.They are only to fool you and most dont have customer service and even if they have the phone nos will not work .so be wise while buying a solar heater