I have purchased a shivalik 25 Litres turbo model with copper Tank, I underestimated the quality of the product by thinking it would be a simple and low rated one but the product was really good after I used it I found the difference.
The geyser would heat water within 20 minutes with a temperature control meter over it I could see the temperature rise fast I had read a few points on the product it has a copper tank which is pure of quality and a double puf insulation that helps retention of heat for a long time. The water remains hot for approximately 4-5 hours which I tested after a cut-off .
Seems like a good product proud the buy one recommended to everyone.