The club were one of more than 20 across Wales who received a WRU Facilities Foundation Grant, which aim to help clubs improve their facilities.
With their floodlights more than 20 years old, Pentyrch used their grant to repair them.
“We have spent a lot of money over the last few years on maintaining our floodlights and now we’ve had the lights on one side of the first team pitch fixed,” said Club Secretary Gareth Williams.
“Without them we couldn’t train. The problem emerged last April and we knew we were going to have problems as the floodlights have been there for over 20 years.”
As well as helping their youth sections to develop, the club hope the new lights will help their first team to improve.
Pentyrch sit in seventh place in Division Three South East and backs coach Berian Davies hopes the opportunity to train longer throughout the winter will see his team climb the table.
“We run a first team, second team and a youth side and Monday nights are the only time the lights are not used,” he said.
“Without the lights there are 350 people who cannot train at all during the winter. There are indoor facilities available but everyone has to travel and it can be expensive.
“It’s crucial that we have them. With the level we’re playing at the boys need to train together as much as possible. When other teams train twice a week, it’s vital we do the same to stay competitive.
“The whole club will benefit including the juniors. We’ve got a full quota from U7 upwards with nearly 300 kids who rely on them too.”
Clubs throughout Wales can apply for the funding with the deadline to apply for the next round ending on January 18.
Clubs are encouraged to discuss any future project ideas with the WRU Club Operations Team.
To apply for future funding, visit http://www.mywru.co.uk.
