Solar Water HEater

Solar Water Heater FAQs

Ulimate answers for your queries regarding solar water heater. Working, Cost, Maintenance & Troubleshooting of solar water heating systems.

1. What is a Solar Water Heater?


Renewgreen Solar Water Heater

A Solar Water Heater is a device which provides hot water for bathing, washing, cleaning, etc. using solar energy.

It is generally installed at the terrace or where sunlight is available and heats water during day time which is stored in an insulated storage tank for use when required including mornings.


2. How does it work?


A Solar Water Heater comprises of a or an array of solar collectors to collect solar energy and an insulated tank to store hot water. Both are connected to each other.

During the day time, water in solar collectors gets heated which is either pumped or flown automatically on thermosyphon principle to the storage tank. Hot water then stored in the tank can be used for various applications.


3. What are different types of SolarWater Heaters?


Two types of Solar Water Heaters are available; one based on flat plate collectors and the other based on evacuated tube collectors. Flat plate collector (FPC) based systems are of metallic type and have longer life as compared to Evacuated tube collector (ETC) based system because ETCs are made of glass which are of fragile in nature.

Both these systems are available with and without heat exchanger. They can also work with and without pump. Systems without pump are known as thermosyphon systems and those with pump are known as forced circulation systems.


4. Which type of solar water heater is suitable for me?


We have to choose size and type of SWH depending upon several factors like the size of family, bathing habits, number of bathrooms, plumbing area, available space for installation, use of pressurised pumps, direction and availability of sunlight, etc.

ETC based systems are cheaper than FPC based system. They perform better in colder regions and avoid freezing problem during sub-zero temperature.

Systems working on thermosyphon principle are simple and relatively inexpensive. They are suitable for domestic and small institutional applications, provided water quality is good and it doesn’t have large chlorine contents. Forced circulation systems are generally preferred in industries or large establishments.

At places where water is hard and have larger chlorine content, if FPC based system is being installed, it must be with heat exchanger as it will avoid scale deposition in copper tubes of solar collectors which can block the flow of water as well reduce its thermal performance. ETC based systems will not block the flow of water but its performance may go down due to deposition of salt contents on inner surface of glass tubes, which could be cleaned easily once in a year or so.

5. What are the pre-requisites of installing SWH at my place?


Based on above (in question 4), a survey of your place will be made by Renewgreen experts and a proper guideline will be provided to you.


6. Do I have to change plumbing at my place to install and use SWH?


Generally not required. Minor changes may require. The hot water supply needs to be attached with cold water with a mixture. Cold water tank to be at high level than SWH system.


7. How long does the water remain hot? Does water remain hot day and night?


The hot water tank of Renewgreen SWH is insulated with a high standard puff. Generally only five to seven degree centigrade loss in temperature, depending upon hot or cold season is taken granted, for a period of 12 hours. Undisturbed water remain comparatively hot.


8. What is the approximate cost of solar water heater ?


Actually purchasing Renewgreen SWH is not an expense or a cost. It is a very good investment and future saving. It not only saves money but also the environment, serves noble social responsibility.

Cost of solar water heater depends on size and type of system installed. Smallest size of a system is 100 litres per day, which means that it can deliver 100 litres of hot water in a day at 60°C. A 100 lpd capacity system is sufficient for a family of 3-4 members and it may cost Rs. 15,000 to Rs.22,000 depending on the type of system.

The system cost does not include the cost of cold water tank, & its stand which is required if overhead tank is not installed in a house/ building. Cost of hot water insulated pipe line also, may be extra if number of bathrooms is more than one. Additional cost towards all these components may increase by 5 to 10%.

The cost, however, does not increase linearly with increase in capacity; rather it comes down proportionately as we go for higher capacity system.

However please check the Renewgreen price list. You will find that comparing to your savings in electricity / gas / coal / wood, the cost will be recovered in two to three years. Then after hot water is totally free of cost. No pollution, no risk will be a bonus for you.

9. Is there any Government subsidy for solar water heater?


At present there is no government subsidy. The saving in fuel is indirect subsidy.


10. Is there finance available for SWH?


Yes. You can avail finance from any credit society or bank by submitting the quotation.


11. Why should I go for a Solar Water Heater? What do I save from it?


100 litre per day capacity system suitable for 3-4 people can save upto 1500 units of electricity in a year, depending on hot water used. It can also save around 140 litres of diesel in an establishment using oil fired boiler besides reducing green house gas emissions in the atmosphere. Higher capacity systems will save higher amount of electricity/fuel oil besides reducing higher amount of GHG emissions.

Electricity is expensive and is not available due to power cuts in many areas when required for heating water. Solar Water Heater, since it stores hot water in an insulated tank, provides water all the time when required. Fuel oil is also expensive and creates pollution. Storing the fuel oil for long term use in commercial establishments is another problem.


Region Northern Eastern Southern Western
Expected no. of days of use of hot water per year 200 200 300 250
Expected yearly electricity saving on full use of solar hot water (units of electricity) 1000 1000 1500 1250
Monetary savings at different prices of electricity, Rs/year
Rs. 4/Kwh 4000 4000 6000 5000
Rs. 5/Kwh 5000 5000 7500 6250
Rs. 6/Kwh 6000 6000 9000 7500

12. What happens on cloudy/rainy day? Do I still get hot water?


On cloudy days also, if it is for a day or two, you still get warm water as water gets heated due to diffused radiation available in the atmosphere. If the sunlight is clear and for more time, the water will be heated more. The technical structure of Renewgreen’s evacuated tubes is made to get maximum benefit of sunlight. But if there is no sun at all, the water cannot be heated.

The temperature of incoming water also plays important role on output temperature. If the temperature of incoming water is too less than required, output water will also moderately hot.

To overcome such situations, an optional arrangement of heating coil is recommended. The provision is made in Renewgreen SWH.

Generally at most of the places in India, sufficient sunlight is available for nearly 300 days in a year.


13. How do I decide about the size/capacity of the system to be installed?


For a house with one bathroom and 3 to 4 members, 100 liter per day capacity system should be sufficient. For more numbers of bathrooms, the capacity will increase accordingly due to pipe losses & more number of family members. Generally the capacity is decided based on hot water required in mornings for bathing. If the usage is in evening & at other times also, the capacity is decided accordingly. Some useful thumb rules for estimating the hot water requirement are given below:


Application Typical Requirement of Hot water at 60°C
Household bathing using buckets 10-20 litres per person per bath
Household bathing using shower with mixing tap 20-30 litres for 10-15 minute bath
Shaving, while a tap runs 7-10 litres
Household bathing in bathtub (one filling) 50-75 litres
Wash basin with a mixing tap (hand wash, brushing of teeth, etc.) 3-5 litres per person per day
Kitchen washing 2-3 litres per person per day
Dishwasher 40-50 litres per wash cycle
Clothes washing machine 40-50 litres per cycle

14. How do I assure that a good quality system is installed at my house?


Ministry has laid down some minimum technical requirements for installation of solar water heating systems in the field. These have been made mandatory for manufacturers and suppliers and are available on MNRE website: www.mnre.gov.in. These requirements are have been prepared in such a way that even a lay man can also check them and ensure that those are being adhered to by the manufacturers/suppliers. Renewgreen’s Solar Water Heaters are strictly manufactured in line with MNRE rules.


15. Are there any maintenance requirements?


The Renewgreen SWH does not contain any mechanical or electrical or electronic device, therefore no maintenance is required.

However as the heating of water depends upon the utilization of sunlight, the outer surface of evacuated tubes shall be kept clean. Those tubes can be kept clean by water wash. If the water is too unclean or hardness of water is high, deposition inside the tubes may be there after certain period. The tubes may be cleaned from inside only through experts. Renewgreen or your dealer will provide you this service in a minor cost.

Occasional leakages in the plumbing could be easily repaired by common plumbers. If outside exposed surfaces are painted, the paint may have to be redone every 2-3 years to prevent corrosion of the surfaces.


16. Any trouble shooting guide for solar water heating systems?


Some of the troubleshooting are mentioned below:


Problem faced Probable cause & remedies
No water in tap  No cold water supply  Wall at the outlet of the system closed  Air lock in the pipes
Water not heated at tall, although cold water flow is normal  Consumption of hot water may be too high; check use points and use patterns  Collector may be shaded  No flow of water through the collector as it may be choked due to scaling; Get it checked from the manufacturer
Water not hot enough, or sufficient quantity of hot water is not available  Cloudy weather  Consumption too high  Frequent on-off of hot water tap  Collector dirty  Vapour lock in the collector which can be removed by allowing to cool & draining the system  Partial chocking of the collector
Little quantity of boiling hot water is received  Vapour locking in the collector  Pinched inlet/outlet pipes


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