eracode:Spark charge 0.6% if you want to pay your monthly bill by credit card instead of direct debit. I really don't like these surcharges but overall I think 0.6% is sort of fair because it sounds like what the bank charges Spark.
Auckland Council charge 1.75% and call it a 'convenience fee'. They say: "This is a bank charge and is subject to change." I don't for a minute believe that a bank would charge a corporate like Spark 0.6% but that AC would be paying 1.75%.
The CC surcharges vary widely, 0.6% sounds very low, it's more usually 1.5-3% so perhaps they get a discount for single larger payments rather than many small ones or for scheduled-in-advance payments.