Spain’s state-owned chain of paradores, the grand hotels often housed in ancient castles and monasteries, has announced that all 97 of its establishments will use only electricity from renewable sources from the start of the new year.

The 90-year-old chain said the decision to switch to green electricity had been made for both environmental and symbolic reasons. “Paradores is a company that supports sustainable tourism in every sense of the word,” said its chair, Óscar López Águeda. “What’s more, as a public company, we also want to set an example when it comes to investments that encourage energy saving and responsible consumption.”

The deal, signed with the Spanish utility giant Endesa, will ensure that all the electricity used in paradores will come from green sources from Tuesday, the start of the new year. However, the company said it has no plans as yet to stop using natural gas.

“Natural gas is less polluting than some of the other sources that hotels have traditionally used,” its head of communications, Sonia Sánchez Plaza, told the Observer. “But we are gradually eliminating our fuel oil consumption and we have an ambitious plan to bring renewable energies into Paradores, including biomass, solar and geothermal energies.”

Sánchez said biomass technology was already being used in two hotels, while solar panels had been installed in other paradores, such as the one in Cádiz, Andalucía. The hotel chain is also looking into harnessing geothermal energy for its hotel on the volcanic island of Tenerife.

Paradores, which was founded in 1928, has more than 4,000 staff and 10,000 rooms. Sánchez said it was in the company’s interests to protect the environment because many of its hotels are close to national parks and biosphere reserves. “We have a lot of environmental projects, both when it comes to enjoying and looking after our surroundings and to restoring flora and fauna and eliminating plastics,” she said.

The move was welcomed by the environmental group Ecologists in Action. “It’s a decision we applaud and which others should now follow,” said the group’s co-ordinator, Paco Segura. “Getting public bodies to make sure their energy comes from renewable sources has a transformative effect. We’ve put together best-practice manuals and have urged public bodies to make sure their plans are based on renewable energy.”

He said some – such as Madrid city council – had already arranged for their energy to come from renewable sources, but many more still needed to follow suit. “It’s great that the paradores are now travelling in the same direction we all need to be going in if we’re going to have a carbon-free economy and carbon-free energy,” said Segura. “The only way to do that is by abandoning dirty fossil fuels that pollute and aren’t sustainable and replacing them with renewable sources.”

Spain is aiming to ensure that its electricity system uses entirely renewable sources by 2050 and then to decarbonise its economy.

Its draft climate change and energy transition law is intended to cut greenhouse gas emissions by 90% from 1990 levels by installing at least 3,000 megawatts of wind and solar power capacity a year for the next decade. The draft legislation will also ban new licences for fossil fuel drills, hydrocarbon exploitation and fracking wells. At the end of October, Pedro Sánchez’s socialist government struck a deal with unions to shut down most of Spain’s coal mines in return for a €250m (£221m) investment in mining regions over the next decade.