Wholesale gas prices in Northern Ireland fell by 43% in May compared to the same period last year, according to a report today.
The energy review and forecast report from supplier Naturgy also said electricity prices were down 17% year-on-year.
Month-on-month, wholesale gas prices were down 4%, while electricity prices were up 0.5%.
And since January, there has been a fall in prices of 49% in both electricity and gas prices.
But despite the falls, larger companies in Northern Ireland are still paying among the highest electricity tariffs in Europe, according to a report from the Utility Regulator.
Despite domestic consumers in Northern Ireland paying rates below the rest of the UK and EU, bigger customers here are at the other end of the scale.
The latest quarterly Transparency Report from the Utility Regulator put domestic electricity prices here at 15.6p/kWh (kilowatt hour), considerably lower than the Republic (22.6p/kWh), the EU median and the UK (both 18.0p/kWh).
But companies in Northern Ireland were at the top end of the price table in the EU.
Manufacturing NI, which represents some of the biggest consumers of the power here, said the status quo significantly undermines competitiveness.
"Our largest manufacturers tend to have the largest bills," said chief executive Stephen Kelly.
"So anything that is a disadvantage price-wise to them is reflected in their competitiveness against competitors in GB and across Europe. Our members have noticed a steep rise in energy prices in the last year and some of that is reflected in the report by the Utility Regulator.
"Three years ago Michelin announced they were planning to close Ballymena over other facilities and their UK managing director at the time made it clear that energy costs was its Achilles heel.
"These things come with consequences and sadly those have been borne out in terms of job losses in places like Ballymena.
"But even on a smaller level, we have firms that have seen their bills rise by tens of thousands of pounds in the last year. That money needs to be found from somewhere and tends to be found in trying to reduce costs elsewhere in their business."
Manufacturing NI has called for pricing to be given the same priority in policy terms as environmental sustainability and security of supply.
David White, of the law firm Arthur Cox, said that the latest market data showed an increase in wind generation, accounting for 35% of the 'day ahead' market in Q1 2019, which was pushing prices down.