The community lies on the East Coast Main Trunk and Murupara Branch railways and is serviced by Rural Delivery route 2. A small airfield was located in Onepu, but it is no longer operational due to the geothermal projects running nearby.
Onepu Spring statistical area, which includes Onepu, covers 98.95km2 (38.20sqmi)[8] and had an estimated population of 1,310 as of June 2025,[9] with a population density of 13 people per km2.
Onepu Spring had a population of 1,293 in the 2023 New Zealand census, an increase of 72 people (5.9%) since the 2018 census, and an increase of 207 people (19.1%) since the 2013 census. There were 648 males, 645 females, and 3 people of other genders in 423 dwellings.[12] 1.9% of people identified as LGBTIQ+. The median age was 43.2 years (compared with 38.1 years nationally). There were 267 people (20.6%) aged under 15 years, 174 (13.5%) aged 15 to 29, 633 (49.0%) aged 30 to 64, and 219 (16.9%) aged 65 or older.[10]
People could identify as more than one ethnicity. The results were 68.9% European (Pākehā); 44.3% Māori; 3.5% Pasifika; 3.5% Asian; 0.7% Middle Eastern, Latin American and African New Zealanders (MELAA); and 3.2% other, which includes people giving their ethnicity as "New Zealander". English was spoken by 97.2%, Māori by 13.0%, Samoan by 0.2%, and other languages by 4.2%. No language could be spoken by 1.6% (e.g. too young to talk). New Zealand Sign Language was known by 0.2%. The percentage of people born overseas was 12.5, compared with 28.8% nationally.[10]
Religious affiliations were 25.8% Christian, 6.7% Māori religious beliefs, 0.7% New Age, and 1.6% other religions. People who answered that they had no religion were 57.3%, and 8.4% of people did not answer the census question.[10]
Of those at least 15 years old, 153 (14.9%) people had a bachelor's or higher degree, 636 (62.0%) had a post-high school certificate or diploma, and 243 (23.7%) people exclusively held high school qualifications. The median income was $43,200, compared with $41,500 nationally. 144 people (14.0%) earned over $100,000 compared to 12.1% nationally. The employment status of those at least 15 was 549 (53.5%) full-time, 144 (14.0%) part-time, and 60 (5.8%) unemployed.[10]
