Listed hydro and thermal electricity producer Mighty River Power attracted an extra 30,000 customers in the year to June.
It represents a gain of nearly 8%. The company now has 412,000 customers.
The gain in residential sales volumes offset a reduction in business with large commercial contracts.
Total electricity generation fell during the year, largely due to a 14% drop in hydro-generation because of drought earlier this year that resulted in the lowest levels at Lake Taupo since 1927.