Horizon Power's managing director says abuse experienced by power company employees “may be understandable but unfortunate”.

The WA state-owned company has been slammed since a billing error in December 2015 saw around 1,200 customers in the west Kimberley towns of Broome and Derby undercharged.

When Horizon Power added the missing charges to the next bill, consumers were hit hard.

That particular bill already included extra costs for air-conditioning of buildings during the unusually hot summer in north-western Australia.

The fallout is now affecting Horizon employees, with managing director Frank Tudor confirming that staff have been yelled at in public.

But he did not direct concerns to official channels, but rather suggests that customers changes their tone.

“I would simply say talk to our people if you have issues, and mostly they will be able to talk through the background,” Mr Tudor told the ABC.

While Horizon Power acknowledges it put customers in a difficult position, but says it will be getting the money back.

“What we've acknowledged is that this is not satisfactory, particularly when people are managing household budgets,” he said.

“[But] he code stipulates that for a 12-month period, if we've been under-billing we have the right to go back and ensure that we get money back from customers,” Mr Tudor said.

“This is not money above what they should have paid, it's money that was legitimately due to us.”

Horizon Power has offered an extension of the bill-repayment period for customers.