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Solar Water Heater

What is 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.
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.
What are different types of Solar Water 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.
Which type of solar water heater is suitable for different places / category of users?
ETC based systems are cheaper than FPC based system. They perform better in colder regions and avoid freezing problem during sub-zero temperature. FPC based systems also perform good with anti-freeze solution at sub zero temperature but their cost increases. In other regions, both perform equally good.

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.
What is the approximate cost of solar water heater?
Cost of solar water heater depends on size and type of system installed. Smallest size of a system is 100 liter per day, which means that it can deliver 100 lietrs 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 in planes depending on the type of system. In hilly & N-E region, the cost may be 15 to 20% more.

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.
Is there any subsidy available from Government?

Yes, the Government provides subsidy to the extent of 30 to 60% to different category of users and States subject to certain benchmarks as per below:

  • General category states for all types of beneficiaries: 30% capital subsidy orloan at 5% interest on 80% of the benchmark cost
  • Special category states for domestic & non commercial categories (not availing accelerated depreciation): 60% capital subsidy orloan at 5% interest on 80% of the benchmark cost
  • Special category states for commercial users category (availing accelerated depreciation): 30% capital subsidy or loan at 5% interest on 80% of the benchmark cost
  • Benchmark Cost :

    ETC based systems : Rs. 10,000/ sq. m.

    FPC based systems : Rs. 11,000/ sq. m.

What is the approximate cost of solar water heater?

Cost of solar water heater depends on size and type of system installed. Smallest size of a system is 100 liter per day, which means that it can deliver 100 lietrs 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 in planes depending on the type of system. In hilly & N-E region, the cost may be 15 to 20% more.

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.

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

A 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.

The table below gives approximate likely electricity and money savings for a typical 100 liters per day system located in different parts of the country.

Northern Region Eastern Region Southern Region* Western Region*
Expected no. of days of use of hot water per year 200 days 200 days 300 days 250 days
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

* The use pattern and savings for southern region pertains to the typical climate of Bangalore, while those for western region relate typically to Pune climate.

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. The system, however, is either connected to an electric geyser in the house or an electrical back-up is provided in the storage tank of the system which is switched on when water is not sufficiently hot. So, you get hot water all the time even on rainy days.
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 60OC
Household bathing using buckets 10-20 liters per person per bath
Household bathing using shower with a mixing tap 20-30 liters for 10-15 minute bath
Shaving, while a tap runs 7-10 liters
Household bathing in bathtub (one filling) 50-75 liters
Wash basin with a mixing tap (hand wash, brushing of teeth, etc.) 3-5 liters per person per day.
Kitchen washing 2-3 liters per person per day.
Dishwasher 40-50 liters per wash cycle
Clothes washing machine 40-50 liters per cycle
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. In case any manufacturer/supplier is found not sticking to these requirements, he may be blacklisted if informed to the Ministry.
Are there any maintenance requirements?
Domestic solar water heating systems do not need significant maintenance requirements. Occasional leakages in the plumbing could be easily repaired by common plumbers. In case quality of water is hard, scale deposition in the collectors may result over the years. This may require de-scaling with acids for which it is best to contact the suppliers. Broken glass may also have to be replaced by the suppliers. If outside exposed surfaces are painted, the paint may have to be redone every 2-3 years to prevent corrosion of the surfaces.
Any trouble shooting guide for solar water heating systems?

Some of the troubleshooting are mentioned below:

Problem faced Probable cause and remedies
No water in tap
No cold water supply
Wall at the outlet of system closed
Air lock in the pipes
Water not heated at all, although cold water flow is normal
Consumption of hot water may be too high; Check use points and use pattern
Collector may be shaded
No flow of water through the Collector as it might 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 it to cool & draining the system
Partial choking of the collector
Little quantity of boiling hot water is received
Vapour locking in the collector
Pinched inlet/outlet pipes

Electric Water Heater

What is the BEE star rating?
A star rating system depicts the energy efficiency of an electrical appliance. The higher the number of stars, the more efficient it is. The star rating system was devised by the Bureau of Energy Efficiency (BEE) India, with a range of 1 to 5 stars.
Is it suitable for salt water?
Yes our electrical water heaters are totally suitable for salt and hard water
Are the inlet and outlet pipes included with the product or do we have to purchase it separately?
In some of the products like Haier Spa series have inlet outlet pipes. Other products do not provide for the pipes.
Does the geyser over heat?
Yes it does if the temperature is set too high and the geyser has not been maintained well.
Is the water heater suitable for high rise buildings or apartments?
Yes it has 8 bar pressure and can withstand pressure in high rise buildings.
Is the tank corrosion resistant?
Yes the tanks resist corrosion but over time it will require basic maintenance
Is it suitable for hard water?
Yes the geysers are suitable for hard water.
Is it possible to control temperature? How to do it?
Many geysers have external temperature control nobs and some have remote control features in them.
What is the minimum and maximum temperature that can be set?
The default set temperature is about 60oC for most water heaters. But some with temperature control functions can set it to as high as 70 degrees C and minimum to 0 degrees C.
How long will the water be hot while taking shower?
Depending on the capacity of geyser you are using the timing will vary from 10 min to 1 hour.
Is it power saver model?
The geysers have thermostats which cut off the electricity when a geyser reached the set temperature and the PUF insulation try’s to maintain the set temperature for long.
Can the geysers can be kept on the loft floor?
Yes! A variant of horizontal geysers known as floor mounting geysers are made to be kept on the loft. It is made with 15, 25,and sometimes 35 litres capacity.
Will I get warranty for my product? If so for how many years?
Yes every electric geyser has warranty. It varies from brand to brand and product to product
How long will it take for the water get hot in winter season?
During winter season the time taken will be between 15 min- 30 min depending on the capacity
What is the power consumption of 15 and 25 litre?
Most of the water heaters use 2 KW power
Can it handle the pressure from the booster pump?
Yes! Water heaters with 8BAR pressure can withstand pressure from a booster pump.
Is the water heater instant or storage?
Electric water heaters come in both instant and storage type. However instant water heater capacity stands for hot water produced per min( 3litre instant means 3litres of hot water per min) and storage capacity means how much water the geysers can store( 10 litre water heater means storage of 10 litres).
Does it have auto-cut feature?
Yes most of the electric water heaters have inbuilt thermostats which give it the auto cut off feature.
Does it have water level indicator?
No the electric water heaters do not have water level indicators.
Can we set timer option using the remote if the option is available?
Yes! On some of the premium electric water heaters this feature of timer and temperature by remote control is there
How many litres of water heater do you suggest for 4 people in an apartment?
Ideally a 25 litre water heater is comfortable for a house for 4 members, but it also depends on your geographical location and the atmospheric temperature and humidity.

Heat Pump

What are the types of heat pump water heater?

There are basically two types of water heaters

  • Instant water heaters (electric and gas)
  • Storage water heaters (electric and solar)
What is a Heat Pump?

Heat pump water heaters use electricity to move heat from one place to another instead of generating heat directly. Therefore, they can be two to three times more energy efficient than conventional electric resistance water heaters. To move the heat, heat pumps work like a refrigerator in reverse.

While a refrigerator pulls heat from inside a box and dumps it into the surrounding room, a stand-alone air-source heat pump water heater pulls heat from the surrounding air and dumps it -- at a higher temperature -- into a tank to heat water. You can purchase a stand-alone heat pump water heating system as an integrated unit with a built-in water storage tank and back-up resistance heating elements. You can also retrofit a heat pump to work with an existing electrical water heater.

Where can I install heat pump?

Heat pump water heaters require installation in locations that remain in the 40º–90ºF (4.4º–32.2ºC) range year-round and provide at least 1,000 cubic feet (28.3 cubic meters) of air space around the water heater. Cool exhaust air can be exhausted to the room or outdoors. Install them in a space with excess heat, such as a furnace room. Heat pump water heaters will not operate efficiently in a cold space. They tend to cool the spaces they are in. You can also install an air-source heat pump system that combines heating, cooling, and water heating. These combination systems pull their heat indoors from the outdoor air in the winter and from the indoor air in the summer. Because they remove heat from the air, any type of air-source heat pump system works more efficiently in a warm climate.

How to Select a Heat Pump Water Heater?

Heat pump water heater systems typically have higher initial costs than conventional storage water heaters. However, they have lower operating costs, which can offset their higher purchase and installation prices.

Before buying a heat pump water heating system, you also need to consider the following:

  • Size and fitting
  • Fuel and availability
  • Energy efficiency
  • Overall cost
Installation and Maintenance

Proper installation and maintenance of your heat pump water heating system can optimize its energy efficiency.

Proper installation depends on many factors. These factors include fuel type, climate, local building code requirements, and safety issues. Therefore, it's best to have a qualified plumbing and heating contractor (or geothermal heat pump system installer/designer) install your heat pump.

Do the following when selecting a qualified professional:

  • Request cost estimates in writing
  • Ask for references
  • Check the company with your local Better Business Bureau
  • See if the company will obtain a local permit if necessary and understands local building codes.

Periodic water heater maintenance can significantly extend your water heater's life and minimize loss of efficiency. Read your owner's manual for specific maintenance recommendations.

Where can I install a Heat Pump Water Heater?
They can go anywhere, but since they cool the space they are in, it is best if they are in a garage or basement or large utility room that doesn’t need to stay warm. They will de-humidify the air so they are great for slightly damp basements.
What if my house is not well insulated?
When you call a heat pump installer for a visit and a quote on a heat pump system, they should do an audit of your insulation and building envelope to make sure the system would work and to identify any obvious insulation work needed. If they do not do this, you should talk to someone else before you purchase. You will save money and be more comfortable whatever heating solution you use if your house is well insulated, but heat pumps are more sensitive to poorly insulated homes because they do not have the brute force of a gas system. A gas furnace can supply very high heat to compensate for poor insulation, although that is a terrible waste of money and energy.
Energy efficiency of Heat Pump Water Heaters

Heat Pump Water Heaters are the best option one has if one wants to save electricity. This is because its efficiency is increased as in addition to consuming electricity, it also takes up heat from the surroundings to heat the water up. So it means that the same amount of water will be heated up in lesser time than in a regular water heater, as total energy consumed is more in case of Heat Pump Water Heaters. How?

If a regular water heater consumes 1 kW to heat up a given quantity of water, a heat pump water heater, in addition to the 1 kW takes up heat from the surroundings amounting to 2.5 kW on the same 1 kW electricity consumed on an average. This means that on the same 1 kW electricity being consumed, a heat pump water heater provides 3.5 kW output (1 kW + 2.5 kW) to heat the same quantity of water. Please not that this value (2.5 kW) may vary according to the brand or specifications of the product you are buying. It can be lower than 2.5 kW and it can be higher than 2.5 kW as well. It entirely depends on the heater that you are buying. So it is advised that you go through the specifications of the product in detail before buying.

How does it affect my savings on electricity?

Let us come down to the part which concerns your expenses on the electricity consumed. The minimum capacity of a heat pump water heater that is readily available in market now-a-days is 50 litres. So let us assume the quantity of water you want to heat is 50 L. Here we consider the two water heaters, a regular water heater and a heat pump water heater.

The total number of electricity units consumed can be found out using a basic formula

Ideal Units for heating = Volume of Water x Temperature Difference x 0.0012

Here the volume of water is 50 L. Let us assume that the temperature of the tap water is 20 oC and you want to use it at 60 oC. So the temp difference is 40 oC (60-20).

Regular water heater Heat pump water heater
Number of electricity Units consumed = 50 x 40 x 0.0012 = 2.4 units Number of electricity Units consumed = (50 x 40 x 0.0012) / 3.5 = 0.69 units

So this means that where a regular water heater uses 2.4 units of electricity, a heat pump water heater uses 0.69 units. And how does it affect your expenses?

Let us assume the tariff is Rs 5 per unit.

Expenditure on 1 unit = Rs 5 Expenditure on 1 unit = Rs 5
Expenditure on 2.4 units = 5 x 2.4 = Rs 12 Expenditure on 0.69 unit = 5 x 0.69 = Rs 3.45

Suppose the water heater is used for 30 days

Regular water heater Heat pump water heater
Total number of units in 30 days = 2.4 x 30 = 72 Total number of units in 30 days = 0.69 x 30 = 20.7
Expenditure on 72 units = 5 x 72 = Rs 360 Expenditure on 20.7 units = 5 x 20.7 = Rs 103.5

The prices of a regular water heater and a heat pump water heater will be different. Usually the price range of a regular water heater is in the range of Rs 10000- Rs 15000 and that of a heat pump water heater lies in the range of Rs 17000 – Rs 25000.

So let us assume the price of a regular water heater is Rs 13000 and that of a heat pump water heater is Rs 20000.

Then the difference in the cost of buying = 20000 – 13000 = Rs 7000

In a month (30 days) you are spending Rs 103.5 if you use a heat pump water heater and Rs 360 if you use regular water heater. So the savings = Rs 360 – Rs 103.5 = Rs 256.5

So how long will it take to recover Rs 7000?

(7000/256.5) = 27 months = 2.25 years (approximately)

It means that if you buy a heat pump water heater (which is costlier than a regular water heater of the same capacity) then in almost 2 years and a quarter, you will be able to recover the extra money you spent on buying the heat pump water heater. And after that, it will all be savings on electricity !

Benefits of using Heat Pump Water Heaters

Heat Pump Water Heaters provide a very suitable and efficient alternative to the regular water heater. Here are a few benefits of using Heat Pump Water Heaters

  • It can heat up large volume of water at a time. They come in different varieties having capacities upto 200 Litres (or more sometimes).
  • These are highly cost effective as they consume lesser electricity to heat up the same volume of water than a regular water heater.
  • They do provide service for a long time. Meaning? They have a long life.
  • They can act as coolers as well as they tend to cool up the place where they are installed.
  • Heat Pump Water Heaters are absolutely safe.
  • The installation requires little effort. Also they are easy to maintain.
Drawback of heat pump
Since a heat pump water heater contains a refrigerant gas, it is important that the heating coils are protected against corrosion. Also since the refrigerant gas might not be environment friendly, so it is advised that it should be properly checked for its ill-effects on the environment.
What are the benefits of a heat pump when used with solar electricity?

Home with a solar panel array on the roof

The benefit of solar panels is that during the day when the sun is shining, your rooftop panels are harvesting solar energy and converting that energy to be used in your home as electricity. In many homes, power generated by the array that is not used in the home is credited back to you by your electric utility company and is used to offset your electric bill at the end of each month. Most homes will still have an electricity bill for power used overnight, during storms, or during periods of high use such as very hot periods of summer.

However, your heat pump is powered by electricity – and when you pair solar panels for electricity with heat pumps for heat (which use electricity for power), you are heating your home for an average of about 9 cents per kWh vs. 14.5 cents per kWh without solar, effectively reducing your cost to run your heat pump by almost 40% annually.

Polymer Tank

What is the Polymer Puff Tank and why do you need it?
  • Most of the overhead tanks today are made from plastic/polymer exposed to the external weather.
  • India is a tropical country and there are states where the summers or winters or both are very extreme.
  • The tank being exposed to the external harsh temperature the water inside the tank is normally at the same temperature of the outer atmosphere which is a big discomfort. For example, in Chennai the temperature in the tank will be over 40 degrees in summer while in North India it will be almost at freezing temperature.
  • The plastic/polymer tanks are exposed to the UV rays and tend to get brittle over the period.
  • To overcome this, Empul has invented the polymer puff tank which provides you comfort. The water inside the tank remains within 5 degrees of the filled temperature. For example: if the water temperature filled is 20 degrees the water inside the tank will be around 15 - 25 degrees depending upon the external temperature.
  • The product is tested at an extreme temperature of -16 deg for performance.
  • Empul Polymer tanks are never exposed to the UV and hence have a long life.
In the present scenario 3/5 layers plastic/ polymer tanks are available in the market. How is the Empul Polymer Tank different from them?
  • The layered tank has thin layers of insulating material. Where the water in the other tanks is generally 5 degrees less than the atmosphere, Empul Polymer keeps water temperature within 5 degrees of the filled water temperature.
  • The Empul Polymer tank comes with varied thickness of Puff 50, 75 or 100 mm based on the external atmosphere.
With several options available of using an aluminium reflector, white or coloured tanks or keeping the tank in shelter why use Empul Polymer Tanks?
  • An aluminium reflector is generally suitable for a hot climate with the downside that it only reflects light but not enough heat. Also, it creates a glare with poor aesthetics. This solution is not suitable in wintertime.
  • The white or other colour tanks are also limited in function with not reflecting enough heat, creating poor aesthetics and also not viable for the cold season.
  • Keeping a tank in a shelter is an expensive proposition as one needs to create a shed on the terrace where the aesthetic is also compromised. A closed shed makes the inner space hot and that is enough to heat the water in tanks.
  • All these shortcomings are overcome by Empul Polymer. The tank is insulated with Puff and is covered with Pre-coated Steel. The cladding sheet reflects the light and puff to avoid heat transfer.
There are options of using other Puff metal tanks? How is Polymer better than them?
  • The SS Tank is susceptible to corrosion in hard water or water with hardness more than > 200 ppm. Empul Polymer tank has resistance to any water quality as there is no metal component in it.
  • The SS Tank is very heavy and increases the lifting and transportation costs. The Empul Polymer tanks are light with ease of handling.
  • For the SS Tank installation, a trained installer is generally needed. It is not 'plug and play'. The Empul Polymer tank comes with an in-built inlet, outlet and overflow provision. The only installation needed is to fix the incoming water line and outlet to the tank.
  • The SS Tank has a stand welded to the tank and is highly susceptible to corrosion. The Empul Polymer Tank has a powder-coated MS stand that is separated from the tank.
Is the Empul Polymer Tank made with Food Grade material?
  • Yes, the material used in making Empul Polymer tank is food grade
  • The material is 100% Virgin polymer with no fillers or metal.
What is the main USP of the Empul Polymer Tanks?
  • Empul Polymer Tanks are one-of-a-kind and launched for the first time in India.
  • The tank solves all the challenges of the existing overhead tank to provide comfort and safety to consumers.
  • It offers the best price to performance in terms of economy.
  • It provides excellent aesthetics and is manufactured with premium quality material.