The findings were in a report by council solid waste manager Ian Featherston, to be considered by councillors during this week's draft 2014-15 annual plan deliberations.
The report came after councillors voted to consult the public on a proposal to add a second weighbridge at the Green Island landfill, following an outcry over the end of discretionary charges earlier this year.
Mr Featherston, in his report, said a three-day trial - putting all 250 vehicles that visited the landfill over the weighbridge - had been carried out during consultation on the draft budget.
Results showed if a second weighbridge was installed, the per tonne charges for general solid waste, green waste and mixed loads would all need to rise to avoid the council falling 13%, or $467,000, short of its budgeted landfill income for 2014-15.
Adjustments to meet budget would result in the general waste fee rising, from the $130 a tonne consulted on for 2014-15, to $145 a tonne instead.
Green waste would rise from $80 a tonne to $100 a tonne, and mixed loads from $110 a tonne to $115 a tonne, his report said.
The charges were used to calculate other individual charges but, despite the increases, 63% of users would still be better off if the second weighbridge was installed, his report showed.
Installation was now expected to cost $110,000, less than the $150,000 estimated previously.
It would significantly cut some users' charges, while increasing others' dramatically, in some cases.
For example, the average cost of a carload of rubbish would decrease to $8.75, down from the flat fee of $18, although the range could fluctuate with use of the weighbridge from as little as $2.90 to as high as $23.20.
A station wagon's average charge would be $13.90, down from the $32 fee, but range from $5.80 to $31.90.
However, while the average cost of a trailer load would increase just $1, to $47, from the flat fee of $46, the range could fluctuate from as little as $26.10 to as much as $226.20, he said.
The council had received 14 submissions on the weighbridge proposal, split evenly between supporting and opposing its installation.
Mr Featherston's report will be considered this week.
