Federally imposed carbon pricing on NB Power will eventually add slightly more than four per cent to electricity bills in the province, but the effect of the policy on New Brunswick's other major emitter — Irving Oil Ltd. — remains a mystery.

With less than two weeks remaining until voters elect a national government, where carbon pricing is a central issue, information on the potential effect the policy will have on New Brunswick industry has been difficult and, in some cases, impossible to come by.

Last week, in a new rate application to the province's Energy and Utilities Board, NB Power revealed for the first time publicly it expects federal carbon costs on it to top out at $67 million per year by 2030, if the province cannot get a provincial substitute plan approved.

That $67 million amount is "significant," according to the utility, although less severe than earlier estimates.

Two years ago, NB Power sketched out worst-case carbon pricing scenarios for itself that included cost increases up to $210 million annually and earlier this year said various revisions in federal proposals had been making it difficult to pin down a reliable estimate.

NB Power's Darren Murphy said cost projections for the carbon levy have changed significantly. (Robert Jones/CBC)

"If you have been following along the play by play, it's changed significantly from last year. You wouldn't even recognize it," said Darren Murphy, NB Power's vice-president and chief financial officer, in May about what federal carbon prices would cost the utility.

"It kind of remains fluid."

NB Power projects sales of electricity to its New Brunswick customers will reach $1.6 billion by 2024. Recovering an extra $67 million to pay for carbon costs would require an increase in rates of about 4.2 per cent, although the utility is still hoping a less strict provincial plan will be approved by the federal government following the election.

"It is recognized that the future of carbon pricing and emission regulation remains highly uncertain," NB Power wrote in material submitted to the utilities board last week.

Ottawa finalized amounts industrial facilities covered by federal rules would have to pay early last summer.

That includes eight facilities in New Brunswick, although two of those, the Irving Oil refinery in Saint John and NB Power's coal and petroleum coke-fired generating station in Belledune, account for more than 80 per cent of the emissions from the group.

But while costs to NB Power of the federal plan have come into focus, the effect on Irving Oil's refinery, if any, remain unknown.

According to federal data, the refinery emitted 3.08 million tonnes of greenhouse gases in 2017, but potentially just a fraction of that amount — possibly none — will be subject to a federal carbon levy.

Canada's oil refineries have been assessed for carbon costs as a group and any facility that achieves an average level of emissions intensity for its production output is required to pay carbon charges on 10 per cent of that.

Oil refineries that are more efficient than average are required to pay less and any facility that emits 90 per cent of the emissions of the average refinery, per unit of production, is to be charged nothing.

Irving Oil's refinery in Saint John is the largest in Canada with a capacity to refine 320,000 barrels of oil per day. (CBC)

"Under (federal rules) industrial facilities pay for their emissions that exceed a set level. Facilities that emit less than the set level, earn surplus credits that they can bank or sell," federal Environment Canada spokesperson Gabrielle Lamontagne explained in an email to CBC News.

Efficiency ratings of refineries are confidential and it is not known whether the Irving Oil facility has been judged to be more or less efficient than the Canadian average and will pay carbon costs on more or less than 10 per cent of its three million tonne total.

The company did not respond to a request for information Monday on how it has been affected by the federal policy.

The New Brunswick government has also put forward a substitute plan for the refinery but Monday said it is not clear how that would change costs the company is receiving from the federal plan.

"If the province does get approval and is able to finalize the performance standard, the facility-specific standards could not be published as it would disclose confidential facility-specific proprietary information," wrote spokesperson Anne Mooers in a statement to CBC News.