The country's seven universities will run an estimated combined deficit of €102 million between last year and this year, the Oireachtas Joint Committee on Education has heard.
The Provost of Trinity College, Dr Patrick Prendergast, told politicians that the Covid-19 crisis has had a severe impact on an already seriously underfunded sector.
He said with an occupancy rate of only 65%, accommodation revenues had "gone through the floor" and ancillary and commercial revenues had been devastated.
Dr Prendergast said the sector was seeking additional funds to cover unavoidable revenue losses.
Raising the issue of student fees, Sinn Féin's Rose Conway-Walsh said it was unethical for students to be charged the full amounts when they were not getting the full experience that they had been promised.
Pointing to the fact that Irish students pay the highest fees in the EU, she asked would refunds be given.
But Dr Prendergast said the cost of delivering education had not reduced by moving online.
"If anything it has increased, in providing the new technologies needed," he said.
Dr Prendergast said Trinity College had seen a doubling of the number of students seeking support with mental health difficulties.
Responding to questions from Senator Eileen Flynn about vulnerable students, Dr Prendergast said the colleges health services were dealing with a much greater need for psychological and counselling services among students as a result of the pandemic.