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Enertiva / Solar water heaters help farmers keep dairies clean

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The cost of electricity is very high in Costa Rica, making heating water expensive for dairy farmers – but not using hot water would compromise the quality of their milk.

Enertiva developed solar powered water heaters especially for dairy farmers, teaming with the milk-purchasing cooperative Dos Pinos, which lends farmers the money to buy them. With the costs of the heaters paid back within a year from the saving in electricity, greater prosperity is coming to the farmers and their communities.

378 solar water heaters installed.

$120 saved per farm per month.

700 tonnes of CO2 cut per year.

"Enertiva is a very focused and dynamic company that’s showing the huge potential to cut the cost of milk production, demonstrating how using solar energy to provide the hot water needed in modern dairies could be applied across the sector in Costa Rica and beyond."

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Costa Rican dairy farmers are enjoying higher incomes thanks to new specially designed solar water heaters that supply hot water for washing their milking equipment and milk tanks. The cost of electricity is very high in Costa Rica, making heating water a major expense for a dairy farmer – but failing to use hot water would compromise the quality and cleanliness of their milk. Solar enterprise Enertiva developed the water heaters especially for the dairy farmers, teaming up with the milk-purchasing cooperative Dos Pinos, which lends the farmers the money to buy them.

With the costs of the heaters paid back within a year from the saving in electricity, greater prosperity is coming to both the farmers and their communities.

Solar powered hot water to clean dairy equipment.


Enertiva started selling solar water-heaters to dairies in 2009. By the end of April 2015, it had installed a total of 378 solar water heaters in 337 dairy farms.

312 of these farms are in Costa Rica, covering about 10% of Costa Rica’s milk production, and most have benefitted from the Dos Pinos loan finance and support. 15 are in Guatemala, and the remaining 10 have recently been installed as a pilot in Panama.

Benefits for dairy farmers

Solar water heaters save money for the farmers who were already washing equipment with hot water. Electricity prices are high in Costa Rica, around US$0.27 per kWh (for comparison: prices in the UK average around US$0.16 per kWh). Enertiva estimates that a typical 60-cow dairy uses about 450 kWh per month to heat water, so saves about US$120 per month. Similar savings apply to those who heat water using gas.

After the solar water heater was installed, my electricity bill fell so much that the electricity company called to check whether the meter was faulty!

Gabriela Arrea, owner, ColiBlanco dairy

Feedback from dairy owners confirms these estimates, and some large farms have achieved much higher savings. One farmer showed the visiting Ashden assessor an electricity statement where monthly charges had fallen by nearly US$300 (from US$885 to 590) after the solar water heater was installed.

The 12 monthly loan repayments are around US$112, which is lower than the cost of electricity replaced so, right from the start, the farm saves money. And once the loan has been repaid, the farm saves around US$1,400 per year, increasing profitability by typically 10%.

Some farmers, particularly those in more remote parts of Costa Rica, process milk into cheese and other products on the farm, and don’t have to meet such strict hygiene requirements for selling raw milk. With solar water-heating, these farmers can produce better quality products by keeping equipment cleaner, and reduce their use of detergent. Even farmers who already use hot water have noted reduced bacterial counts in their milk, probably because extra cleaning is carried out when the hot water is ‘free’.

Oscar Duran, manager of Ledo Maria dairy, using solar-heated water to wash the milking equipment.

Environmental benefits

Costa Rica generates about 93% of its electricity from renewables, mainly hydroelectricity, one of the highest contributions in the world. Fossil-fuel generation is used to top up when the demand exceeds the supply from renewables. This can occur during daily demand peaks, or else when there is a lack of rain to provide water for hydroelectric plants. Replacing electric water heating with solar water heating helps offsets this use of fossil fuels.

The 378 solar water heaters in use in dairies avoid about 2,000 MWh of electricity per year.  An estimated 40% of this replaces fossil fuel use and thus cuts about 700 tonnes/year of CO2.

2017 Update…

  • The number of full time employees has increased 11%.
  • The tonnes of CO2 saved this year have increased 12%.
  • Their total number of products sold has increased 12%.


Enertiva’s Award shows how dairy farms in many tropical countries could increase their profitability using solar water-heating. Having covered about 10% of the dairy sector in Costa Rica, Enertiva has started installations in Guatemala and Panama.

The business model

The basic business model of Enertiva is designing, selling and installing solar technology. It also undertakes research and development contracts for others. Enertiva’s directors only promote solar systems which they can show to have a return on investment of less than seven years. To achieve this, they focus on eliminating the barriers to making the technology cost-effective in a particular setting, in particular technical and financial barriers. This approach has been applied with great success to solar water-heating in dairies and to their other work.

We always follow Dos Pinos cleaning rules, so our milk always passes their quality checks. But I’ve noticed that there’s less sediment in the pipes since we had the solar water heater, that’s got to be good.

Oscar Duran, manager of Ledo Maria dairy

How do solar water-heaters work and how are they used?

An ‘evacuated tube’ design of solar water-heater is used for dairies, manufactured in China to Enertiva’s specifications. It has a row of glass tubes, filled with water and connected to a highly insulated water tank. Sunlight heats the water in the tubes and thus the water stored in the tank heats up though the day.

The solar water heater is mounted on the roof of a dairy, with the tubes sloped at about 15o to the horizontal and facing towards the equator (South). This slope gives high year-round solar collection and allows the heated water to rise and circulate.  The tank inlet is connected to the cold-water supply of the dairy and hot water is taken from the outlet.

Ledo Maria dairy has a 5,000 litre refrigerated tank that has to be thoroughly washed every two days.

Enertiva gives a 5-year warranty on the system and expects that it will last for 20 years. The only maintenance needed is to wash the outer tubes of the collector every month, to prevent dust and debris from blocking sunlight. Users are trained to do this.

Removing technical barriers

Dairy farms that sell to Dos Pinos milk their cows twice per day and store the milk in a refrigerated tank to be collected by the cooperative on alternate days. The milking equipment should be washed after each use, and the milk tank after each emptying. A strict washing schedule is set by the cooperative, with a cold wash, followed by a detergent wash and finally a 50oC hot wash. Dos Pinos rejects milk that is contaminated, by measuring bacterial content before accepting milk for collection, and it pays a premium for the highest quality milk.

Afternoon milking at Colle Blanco dairy farm.

Enertiva recognised that, for solar water-heating to fit with this washing schedule, it was essential to have sufficient hot water at the correct temperature, at the times when the dairy farm wanted to use it. Technical modifications were therefore made to the solar water heater. One is a thermostatic mixer on the outlet, used to reduce the water temperature if it is too high. Another is a small electric heating element in the water tank, used to boost the water temperature if it is too low. The control system that Enertiva designed and built to do this checks the temperature of the water in the tank three hours before it will be used, and switches on the element if the temperature is too low. Controls are set according to the times of milking and milk collection for the specific dairy.

Removing financial barriers

The installed cost is around US$1,200 for the most popular solar water-heater which has 20 tubes (4 m2 area) and 200 litre tank. Although some dairy farmers buy outright, many find this cost too high.

The solar water heater gives us plenty of hot water for mixing up the calf food as well as for cleaning the milking equipment.

Luis Chaves, manager of La Vistada dairy

Enertiva therefore proposed a solar loan scheme, which Dos Pinos has taken up as part of its environmental programme. The cooperative provides loans to its farmers to buy solar water-heaters at an annual interest rate of 14%, and promotes the loan programme through its network of agricultural supply stores and advisors.  Dos Pinos has identified dairy farms in each region as examples of best practice, and all of these have solar water-heaters.

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