Europe has met a landmark goal of slashing its energy consumption six years ahead of time, cutting greenhouse gas emissions equivalent to switching off about 400 power stations.

In 2014, the EU’s 28 member countries consumed 72m tonnes of oil equivalent less than had been projected for 2020, according to a report by the EU’s science arm, the Joint Research Centre (JRC). The figure matches Finland’s annual energy use.

Environmental campaigners described the achievement as “remarkable”. and “incredible” but the European commission was restrained.

“Final energy consumption is currently below the 2020 target,” a spokeswoman for the commission said. “The EU-28 are are also on a good pathway to achieving the primary energy consumption target for 2020 if current efforts are maintained.”

Major energy savings were reported across all sectors in the study, with EU legislation driving efficiency gains in electrical products, industry installations, fuel economy and the housing sector.

Energy use in residential buildings fell by 9.5% between 2000 and 2014, second only to the industrial sector, where there was an energy drop of 17.6% over the same period.

But energy analysts were concerned that the UK government – seen as dragging its feet on energy efficiency measures – could move in the opposite direction once no longer bound by EU legislation.

Ingrid Holmes, the director of the E3G thinktank in London, said: “Brexit creates enormous uncertainty over how the UK will continue to provide affordable and secure energy to its people. Energy efficiency works – and it’s time the government committed to at least match the ambition of energy saving actions taken by the rest of Europe.”

Several EU directives maligned by Eurosceptics and industry groups played a key role in reaching the non-binding efficiency target of reducing final energy use 20% by 2020 compared with projected use that year, according to the report. These included laws on energy efficiency, eco-design, buildings performance and fuel economy.

By contrast, the fast-growing service sector, which was left untouched by EU directives, recorded a 16.5% spike in energy use.

Adrian Joyce, the secretary general of EuroAce, the building efficiency group, said: “The building sector made a massive contribution to this achievement, particularly residential buildings, which politicians see as the toughest part to reach.”

“People might find it incredible that we reached our final energy use target ahead of the deadline but it is a demonstration of what good EU policy can achieve.”

The EU has set a 27% efficiency goal for 2030, and could potentially increase it next month when the commission brings forward a raft of efficiency measures.

The focus will be on updating buildings and efficiency directives, with an outside chance that the eco-design plan could also be published.

That blueprint, with its widely trailed short-circuiting of wasteful toasters, was delayed by fears that tabloids would campaign over the issue during the EU referendum.

Eurosceptics and environmentalists may at least be united in pointing to the JRC report’s cautioning that financial crisis played a part in several countries’ reductions in energy use. “It has contributed to get energy consumption back on track towards the EU energy and environmental targets for 2020,” the study said.

Pieter de Pous, policy director at the European Environment Bureau, said: “We need a real decoupling of energy use from economic growth or the moment the economy picks up, we will be back to square one.”

While the EU met its final energy use target in 2014, it was 1.5% shy of its primary energy goal, which could yet be affected by any squandering of energy in the next five years.

“Without the economic crisis we would not be here,” said Monica Frassoni, the president of the European Alliance to Save Energy. “We need more measures and stringent targets.”