Located in Swindon, the hospital was not selected for the latest investment in health hubs across the south west.
Eight NHS trusts in the region were awarded a total of £4 million to introduce clean energy solutions and improve energy efficiency.
The upgrades will help to bring down their bills and create savings that can be reinvested into local frontline services.
More than £2.7 million of the investment will go towards installing batteries and solar panels, in partnership with Great British Energy.
This builds on the publicly owned energy company’s £255 million investment in solar power for hospitals, schools and military sites last year.
A spokesperson for the Great Western Hospitals NHS Foundation Trust said: “We continually review funding opportunities that support improvements to sustainability and energy efficiency where they align with our needs and priorities.
“In this instance, the funding criteria did not match our current requirements, as we have already implemented clean energy technology, including over 99 per cent LED lighting across the hospital site.
“In addition, the Trust’s Energy Centre powers our Urgent Treatment Centre and Emergency Department, providing one of the most sustainable sources of power currently used on our site.
“We continue to work towards reducing environmental impact to achieve net carbon zero by 2040.”
The Royal Devon and Exeter Hospital will receive £1.9 million for new solar panels and battery systems.
Elsewhere in the region, Salisbury District Hospital has been allocated £228,000 for similar improvements.
No other health facility in Wiltshire was included in this funding round.
Outside the healthcare sector, HMP Channings Wood in Devon will receive £495,000 from GBE for solar panels, along with almost £250,000 for electrical and plumbing works to improve efficiency.
This initiative is part of a broader £74 million government scheme to help public buildings generate their own electricity and save tens of millions on their bills.
Dan McGrail, CEO of Great British Energy, said: “Communities are at the heart of our mission to make Britain a clean energy superpower.
“Clean local energy projects enable communities to directly benefit from cleaner, more secure power.
“This funding will help to create an immediate reduction in energy bills so that millions of pounds can be invested back into vital services for the British public.”