The ESB has reported pre-tax profits of €70m for the six months to the end of June, down from €236m the same time last year.
In its results statement, the company said that its revenues for the six months fell to €1.647 billion from €1.72 billion.
Its operating profits reduced by €50m to €287m, which reflected the impact of weakening sterling on earnings following the Brexit vote.
During the six month period, the company said it spent €356m on capital expenditure, down €49m on the same time last year.
The group is organised into five main strategic divisions, all of which are managed separately.
Its Generation and Wholesale Markets division reported an operating profit of €112m, down €28m on 2015 mainly due to a lower energy margin as a result of lower wholesale electricity prices.
But its Networks division saw operating profits rise by €20m to €148m on the back of higher network usage and a change in regulated tariffs.
Operating profits at the ESA's Northern Ireland Electricity Networks division rose by €2m to €15m due to higher regulated tariffs, which were partially offset by negative foreign exchange movements.
The ESB said its Electric Ireland's operating profit of €57m was up €32m on last year, due to lower electricity prices and positive hedging movements.
Another division of the business include Innovation, Corporate Centre and the Business Service Centre which provide services to the main business segments above.
This segment, which includes most of the financing costs of the Group, reported an operating loss of
€45m compared to a profit of €32m profit in 2015.
The company said this mainly related to a foreign exchange translation loss on sterling denominated intracompany positions.