Grouby is an irreplaceable member of his rescue crew, having been involved in key rescues on Rotorua's lakes, including the rescue of four kayakers stranded on the freezing lake in the winter of 2016.
"It's not the sort of thing I ever thought I would be going to," Grouby told the Rotorua Daily Post.
He is looking forward to the trip, being inside the palace, and hopefully meeting Prince Charles.
Grouby said he lived in the United Kingdom for two years and had visited Buckingham Palace before, but only from the outside.
"It's going to be different being on the inside looking out."
He said Coastguard New Zealand on a whole was quite big and did "a hell of a job" around the country, so it was great to have recognition from Prince Charles.
He will be heading to the reception in London with his wife Sharryn.
Grouby said she was not a member of the Coastguard, but one thing about Coastguard volunteers was they had wives getting behind them in the background as the volunteers put in their time.
"I think she deserves it as well."
Coastguard chief executive Patrick Holmes said the organisation was incredibly honoured to have such a high calibre of volunteers representing Coastguard at the reception.
"Barry, Mike and Ross are all exceptional volunteers who have contributed their time, energy and talents into their units to a remarkable degree, and will represent us with pride at this prestigious event.
"To have them represented on an international stage at a significant celebration is a huge boon for Coastguard and New Zealand in general."
The Prince of Wales has played an important role in Coastguard's history, becoming the organisation's patron in 1985 when it officially became the Royal New Zealand Coastguard Federation.
He also visited Coastguard during his tour of New Zealand in 2012 and has always supported Coastguard's mission of saving lives at sea.
