In the past three months, there have been a dozen reports of stolen califonts, most in the Counties Manukau area.
Photo: RNZ / Richard Tindiller
Offenders have been targeting new housing developments and subdivisions and it's believed they're onselling the systems through Facebook marketplace and other platforms.
There's also evidence many of the gas hot water systems are damaged during the thefts, potentially creating safety issues.
"We also want to remind the public that deals advertised online which appear "too good to be true", are often cheap for a reason,' acting inspector Jono Chappell said.
"Purchasing these items through unregulated channels such as through social media rather than reputable retailers puts your own safety at risk by using items which are potentially damaged.
"Receiving stolen property is a criminal offence and you may face prosecution."
Police say builders, developers and homeowners should record the serial number of their califont.