The value of volunteering by older people in the UK is expected to be worth more than £15bn by 2020, according to the Commission on the Voluntary Sector and Ageing.
The commission, which was set up last year to examine and prepare for the challenges and opportunities presented by an ageing population, says in its first report today that the value of voluntary work done by people aged over 65 will be worth £5bn more in 2020 than it was in 2010.
The report, Age of Opportunity: Putting the Ageing Society of Tomorrow on the Agenda of the Voluntary Sector Today, says that rather than perceiving an ageing society as a burden, the voluntary sector should be looking at the "opportunities that this older, mostly healthy, population brings".
The report says that skilled and experienced older people are retiring "in droves" and charities urgently need to adapt to the ageing population to exploit this opportunity if they are to thrive in the future.
It maps a set of future scenarios describing how charities might thrive or struggle in the future, depending on the choices they make now and poses "discussion points" for charities.
Lynne Berry, chair of the commission, said the voluntary sector was at a crossroads because of dramatic changes to society that would occur over the next 20 years, but the rewards would be substantial if organisations started planning now.
"People retiring today are more skilled and more savvy than any generation before them, and they will bring years of experience and expertise to charities," she said.
"This is the generation that brought us sweeping changes through the gay rights movement and environmental campaigning, and they can share their own skills while picking up new ones from younger colleagues in return. They are now ready for new commitments, using their skills in their various communities.
"This is a recipe for helping the sector stay resilient and becoming more creative and more connected long into the future. An ageing population can bring massive benefits to charities provided preparations are made now."
But she also warned that older people were under pressure to care for grandchildren and support local causes, so charities would need to make extra efforts to attract and keep people.