Power company Vector is warning customers to be extra vigilant after a data breach revealed the names, phone numbers and email addresses of up to 24,000 users of its app.
The app's been popular following this month's severe storm in Auckland, which caused widespread power cuts.
Vector says someone with IT knowledge was able to access the information, which could also lead to the identification of home addresses.
The data breach hasn't compromised the security of Vector's financial or electricity network systems.
The app has been shut down to be rebuilt.