Costa Rica has achieved a clean energy milestone by using 100 per cent renewable energy for a record 75 days in a row.

The feat was achieved thanks to heavy rainfall, which powered four hydroelectric plants in the first three months of the year, the state-run Costa Rican Electricity Institute said.

No fossil fuels have been burnt to generate electricity since December 2014, in the state which is renowned for its clean energy policies.

While Costa Rica is a small country, with a popular of about 4.8 million people, it has made great strides in its use of renewable energy.

Last year 80 per cent of the energy used came from hydropower, while geothermal energy made up about 10 per cent of the mix in the volcano-strewn nation. Currently 94 per cent of Costa Rica’s energy needs are met by renewables.

New geothermal projects are already in the planning stages, to ensure that the Central American state does not have to rely on fossil fuels in the future.

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The government approved a US$958 million geothermal project in mid-2014.

The first plant, when completed, is expected to produce 55 megawatts of electricity, enough to power 55,000 homes. A further two 50 megawatt plants will be built nearby.

Jake Richardson, of Clean Technica, said it was important the country did not become too dependent on hydropower.

“It’s good news that more geothermal will be coming on board, as there are obvious downsides of being too reliant on hydropower, especially run-of-the-river systems, which can be hindered by seasonal changes in water flow,” he told Science Alert.

“Droughts can also severely impact power supplies. And there are also some environmental downsides to hydroelectric dams more generally, namely the impact on riparian ecosystems and passing fish.”

It helps that Costa Rica, which aims to be carbon-neutral by 2021, has excellent infrastructure.

The World Economic Forum ranked the country second in Latin America, behind Uruguay, for its electricity and telecommunications infrastructure in its 2014 Global Competitiveness Index.