Which is the best solar water heater to buy which will suit my requirement ? This is the primary question that troubles every new house owner these days. Some state govts have also made it mandatory to have a solar water heater installed. So, here are some of the points to consider before making that purchase.
What is the quantity of usage ?
How many people live in the house who use hot water and do you use just for bathing or to wash clothes / utensils etc ?
Just for bathing purpose, consider using 100LPD for 2-3 people, 200 LPD for 5-6 people as a guidance. You will get an idea of the usage. Accordingly plan for capacity
Flat Plate Collectors (FPC) or Evacuated Tube Collectors (ETC) ?
ETC based solar water heaters are known to perform better than the FPC. The design and flexibility is superior. For a more detailed explanation read this article – Flat plate collectors vs. evacuated tube collectors
Do you have hard water problems ?
A simple water test can determine what is the TDS (total dissolved salts) present in your water. If it’s high (> 250ppm), most ETC based solar water heaters are able to handle that. However over a few years, the hard water will start taking it’s toll on the solar tank and piping systems. The calcium and magnesium salts will start depositing inside and start to corrode them. This will result in fast degradation of the solar water heating system whichever brand you buy. This will result in repair costs much earlier than you thought. We get calls from customers who have installed the equipment for just about 3 years and tanks have started leaking. Here, we recommend using a scaling prevention system (from 3M as this does not use electricity and works on patented filtration technology that reduces scaling without losing essential minerals). So, even if the costs are slightly higher, as a combined system, in the long run, the combination of solar water alongwith a 3M scaling prevention system will save costs big time and saves you trouble from frequent maintenance of plumbing systems.
See here for more details – 3M whole house scaling prevention system