The Bord Gáis Energy Index fell by 37% in March due to an unprecedented drop of 55% in oil prices as Covid-19 spread to every corner of the globe - hitting growth and energy demand.
Brent crude prices closed at an 18-year low of $22.7 a barrel in March, a drop of 55% over the month.
The big drop in March was the result of falling oil demand and a breakdown of the OPEC+ supply restraint agreement.
Bord Gáis said the ever-tighter restrictions in place to combat the spread of Covid-19 have seen an unprecedented drop in oil consumption, with whole sectors of the global economy in shutdown.
"On top of this unprecedented demand shock, an agreement that had been in place since 2016 between OPEC and Russia to restrain oil production collapsed, leading to greater supply and driving prices lower," it added.
Bord Gáis also said the gas market, already awash with supply before the spread of the coronavirus, fell a relatively muted 3%. Gas markets had already been weak for much of the past year due to a mild winter, a weakening economic outlook and a surge of LNG.
Gas prices were dealt a further blow as demand fell further due to extensive restrictions put in place to combat the spread of Covid-19.
Bord Gáis said a 5% reduction in electricity demand was more than offset by a reduction in wind output to result in higher day-ahead power prices.
It said that wind provided 44% of total power generation in March compared to 56% in the previous month, with lower power generation from wind typically leading to higher electricity prices.
Meanwhile, coal managed to gain 3% in euro terms in March with the resumption of economic activity in China probably behind the rally, Bord Gáis added.