The funding, repayable on an Invest to Save basis, will support energy projects being delivered by Swansea Bay University Health Board (SBUHB), Cardiff and Vale University Health Board and the Hywel Dda University Health Board.
It builds on £2 million provided last year as part of a larger £17 million programme.
The latest funding includes £2 million in COVID-19 recovery funds, earmarked for a proposed 4MW solar project for SBUHB, which will help power Morriston Hospital in Swansea.
Combined with an ongoing £7.7 million retrofit programme, it is expected to save the health board more than £1.6 million per year on energy bills.
The solar farm, subject to planning permission, will be located at Brynwhillach Farm and linked to Morriston Hospital by a 3km long private wire.
A further £3.8 million is expected to allow the health board to complete the solar farm by the end of 2022.
Cardiff and Vale University Health Board is being granted a further £600,000 to expand its work to improve energy efficiency across its estate and Hywel Dda University Health Board will receive £1.75 million to install solar panels on buildings across its estate, in addition to other energy efficiency measures.
Each of the health boards worked with the Welsh Government Energy Service – which provides advice and support on energy to communities and public bodies – to identify opportunities to improve their energy efficiency and increase the use of renewable energy across their estates.
Environment, Energy and Rural Affairs Minister Lesley Griffiths said: “As we look towards making Wales a carbon-neutral nation, we want to do everything we can to support public bodies, such as health boards, to minimise their carbon output through efficiency measures and to use renewable options wherever possible.
“I would like to thank each of the health boards for the work they have already undertaken in this respect; and would especially like to thank Swansea Bay University Health Board for their ambition, as they work towards creating a new solar farm, which will help power Morriston Hospital.”