MADRID, Jan 4 (Reuters) - The amount of electricity consumed in Spain fell 2.3% for a second straight year in 2023, raising concerns of a supply surplus as the renewable sector ramps up more quickly than fossil and nuclear-fuelled sources wind down.

With renewable sources breaking records and the government planning to massively increase their contribution to the energy mix in coming years, lacklustre electricity demand is a growing issue for the renewable industry.

Spanish demand for electricity stood at 244,686 gigawatt hours (GWh) last year following a 2.3% decline in 2022, provisional data released by grid operator Red Electrica showed on Thursday.

The drop was driven by depressed demand from Spain's industrial consumers, which are still reeling from the impact of the energy crisis.

Industry lobby group APPA Renovables on Wednesday called for policies to support electricity consumption, such as boosting the adoption of electric vehicles.

Renewable sources like wind and solar produced a record amount of energy and accounted for an unprecedented 50.4% of the electricity generated in Spain last year, according to Red Electrica data.

Wind farms replaced gas plants as the country's main source of electricity, covering more than 23% of demand.

Gas plants, known as combined cycle power plants, accounted for roughly 17% of the electricity consumed in the country, a sharp decline from the previous year, when their contribution was almost 25%.

Electricity demand is just one of the issues threatening to affect the deployment of renewables in Spain at a time when the country needs to speed it up to meet its ambitious green goals.

Depressed wholesale electricity prices are affecting profitability, APPA warned, and utilities such as Endesa and Naturgy signalled a slowdown in renewable energy development in the face of high interest rates and rising debt costs. (Reporting by Pietro Lombardi; Editing by Jan Harvey)