He said it was great to have people choosing to listen to something that was local and broke away from all the seriousness in life.
With more listeners, he had more of an opportunity to give back to the Tauranga community, he said.
Johnston's daytime show scored an award at the New Zealand Radio Awards last week in the category Best Music Non-Breakfast Solo Host - Non-Network.
Local Coast presenter Brian "BK" Kelly also swept the stage, coming out as the number one local breakfast show broadcast from Tauranga for all people over 10 years old in station share.
NZME's Bay of Plenty general manager, Greg Murphy, said it was positive to see more people listening to NZME's shows and, more importantly, their local announcers.
He said Johnston engaged well with his listeners and it showed with his great results, and BK's local connection played a huge part in the fact that Coast was so dominant across the company's local market.
NZME's Newstalk ZB grew its dominance of the commercial radio networks, with multi-award-winning hosts Mike Hosking and Marcus Lush streets ahead of their competition.
Nationwide, Newstalk ZB came out as number one in its Early Edition, Breakfast, Drive, Nights, Overnights and Weekends across New Zealand.
On the music scene, ZM's breakfast hosts Fletch, Vaughan and Megan topped the charts and took away the title of number one breakfast show for 18 to 34 year old Kiwis.
The NZME network saw "super-charged growth in 25 to 54 audiences nationwide", with every NZME station growing in popularity with these listeners, said NZME's head of commercial, Matt Headland.
NZME chief executive Michael Boggs attributed the radio audience growth to a relentless focus on having the best hosts on the right brands building meaningful and lasting connections with listeners.
Boggs said the station had put many new shows in place with hosts like Kerre McIvor and Heather du Plessis-Allan, Simon Barnett and Phil Gifford and that hard work was being recognised by the listeners.
He said nearly 3.4 million New Zealanders listen to commercial radio each week and they were listening on average for 17 hours a week.
NZME's streaming service iHeart Radio was also doing exceptionally well, boasting just over 878,000 registered users and clocking up 3.4 million listening hours in May.
Source: GfK Radio Audience Measurement. Commercial Radio Stations. Tauranga S2/2019 (NB: Waikato S3/2017).