The penalty falls under the Electricity (Hazards from Trees) Regulations 2003, which define "growth limit zones" around power lines, ranging from 50cm to 2.5m, which dictate how much trimming was needed.
Consumer New Zealand chief executive Sue Chetwin said the law applied to lines on or above private property.
"We've got advice on it, so that usually means we've had some issues on it," she said.
"Our advice is that the lines company will pay for the first time the tree has to be cut but after that, you have to take care of it."
Tree owners who ignored a "cut and trim" notice could face daily fines of $500 and be liable for costs if their tree damaged power equipment.
Labour's energy spokesman David Shearer was surprised to hear how heavy the penalties for property owners could be.
"My initial response is it's a steep penalty ... I would hope that Vector would be working with the owner to come to an agreeable situation."
Vector, one of many New Zealand lines companies, said trees caused one in four outages and hindered crews repairing equipment and restoring power after blackouts.
Gripes about tree trimming regulations could be sent to the Electricity and Gas Complaints Commissioner.
But the commissioner's case files showed complaints about lines companies not being zealous enough, rather than draconian fines.
In 2012, a man said a lines company did nothing about a tree too close to a power line on his property.
He said he should have received a "cut and trim" notice but never did. The tree hit a power line during a storm, "which created a fireball".
The man the took a chainsaw to the tree - but injured himself in the process.
The lines company paid the man $500 because the tree had not had its first cut and trim.
Some people needed resource consent to cut trees - but Vector said this was usually limited to "council trees with amenity value".
Vector contacted arborists to inspect all lines and carry out trimming as legally required, or to advise tree owners of work needed.
A Vector spokeswoman said the company had always been able to reach agreement with tree owners but could as "a last resort" escalate matters to Energy Safety, a Ministry of Business, Innovation and Employment (MBIE) division.
Vector said most trees in Auckland were receiving their second or third trims, except recent plantings or younger trees that were just growing up into the lines.
Taking care of your trees
•Trees inside the "growth limit zone" will spark cut and trim notices
•Bigger clearances are needed for lines with longer spans
•Any shrubbery within 2.5m, in any direction, from a 33kV line must be cut
•Any shrubbery within 1.6m from an 11kV line must be cut
•Any shrubbery within 50cm from a 400 or 230kV line must be cut
