One of those things that you may not be aware - some electricity retailers charge you fees depending on how you pay your electricity bill.
Mercury Energy is the worst offender charging fees to take credit card payment over the phone, fees for processing cheques, and fees for paying at NZ post.
TrustPower charges customers to pay at the Postshop also.
Genesis Energy and Contact Energy at this stage do not appear to charge fees for any payment method.
But it's something to pay attention to.