For more than 250 days of 2016, Costa Rica ran entirely on renewables.

It was the second year running that the Central American country of 4.9 million people powered itself on 100% renewable electricity for more than two thirds of the year.

Over the course of 2016, renewables supplied 98.1% of Costa Rica’s electricity, slightly down from the 98.8% achieved in 2015.

On days when Costa Rica did not generate all its electricity from renewable sources, the extra capacity came from diesel-fuelled thermal power plants, a spokesman for the Costa Rican Electricity Institute (ICE) told Mashable.

Image: ICE

As the graphic above shows, hydropower is Costa Rica’s dominant energy source, accounting for almost three quarters of electricity generation in 2016. It is followed by geothermal energy, which provided 12.74% in 2016, then wind power at 10.3%, diesel-fuelled thermal power plants at 1.88%, biomass at 0.72%, and solar power at just 0.01%.

Renewables without hydropower

Hydropower is currently the largest single renewable electricity source, providing 16% of the world’s electricity, according to the International Energy Agency. It’s also a relatively cheap form of energy, but there are concerns about its environmental impact – the dams required to create hydropower plants can alter ecosystems, harm fish stocks and impact the lives of local people.

Like nuclear, hydropower provides a stable base load that renewable electricity sources like wind power and solar photovoltaic are unable to match, due to their intermittency.

Indeed, countries that produce close to 100% of renewable electricity tend to share two features in common – relatively small populations, and large hydropower generating capacity relative to energy demand.

According to data from the World Bank, both Albania and Paraguay generated 100% of their electricity from hydropower in 2013.

Iceland, meanwhile, generated 100% of its electricity from renewable sources: 71% from hydropower and the bulk of the remainder from its extensive geothermal resources.

The total amount of electricity generated by Albania, Paraguay and Iceland combined in 2013 was 85.5 terawatt hours (with 60.4 terawatt hours generated by Paraguay). To put this in context, the world’s largest electricity producer, China, generated 5,422 terawatt hours over the same period – two thirds of which came from coal-fired power plants.

When hydropower is taken out of the renewable electricity mix, the proportions fall considerably from 100%:

This chart shows electricity production from renewable sources, excluding hydroelectric (% of total)

Image: World Bank

Wind power pioneer Denmark leads the way, while Iceland still performs strongly thanks to its geothermal resources.

However, these figures are from 2014, and as a result Costa Rica’s rapid growth in wind power installations are not included. The country’s investment in wind farms in recent years means it is on schedule to more than double its wind generating capacity from 194 MW in early 2015 to 393 MW in 2017.

The 10.3% of its electricity generated by wind power in 2016 meant that 23.8% of Costa Rica’s electricity in 2016 came from renewables excluding hydro – beating more than half of the top 10 countries ranked by the World Bank in 2014.

Sustainable development

In the World Economic Forum’s Global Energy Architecture Performance Index (EAPI), Costa Rica is ranked 14th out of 127 nations.

Image: EAPI