State power utility Perusahaan Listrik Negara (PLN) bills its customers in rupiah, but it needs about $600 million in foreign currency every month to pay local coal miners and power producers and to service its loans.
Under the new regulation, PLN's payments to local producers can no longer be in dollars, and while that would in theory suit the company, in practice, the rupiah price it pays will still be determined by dollar exchange rates.
"We are still negotiating, but even when we agree to set the contract in rupiah, we have to discuss the exchange rate that will be used," says Tjutju Kurnia, head of treasury at PLN.
Its vendors have liabilities in dollars, she said, so they have to build in foreign exchange risk.
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Some vendors, such as state-controlled coal miner Bukit Asam , with whom PLN has two power purchase contracts, have already adopted settlement in rupiah, but they still quote prices in dollars.
Bukit Asam's corporate secretary said the firm had a calculation system in place and every dollar cost in their investment or production activities was converted into rupiah.
Heavy equipment distributor and mining contractor United Tractors sells all its products and services in dollars "simply to match cash in and cash out", said corporate secretary Sara Loebis.
Loebis said United would comply with the new rules but it might mean more risks for the firm.
In the textiles industry, Indonesia's second largest manufactured goods exporter, every transaction in the supply chain except labour costs is in dollars.
Electricity bills are settled in rupiah but they fluctuate every month because the charges are dollar-based. The fibre and the spinning industries also pay for raw materials in dollars and sell products locally in dollars.
"If Bank Indonesia requires this industry to convert their dollars to rupiah, I'm afraid their prices will not be competitive with products that are directly imported," says Ade Sudrajat of Indonesian Textile Association.
Leo Putra Rinaldy, an economist at Mandiri Sekuritas, warns that an unintended consequence of the new rules could be inflation, as companies err on the side of inflated rupiah values to hedge against currency swings.
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"There would be companies that set the rupiah exchange rate based solely on their expectations, and mark them up," said Rinaldy. "If you are a single producer or single supplier, you have the power to do that, but if it is a competitive market, buyers would look for better pricing."
Such incidental costs weigh against the benefits of the new regulation, which doesn't address the main source of rupiah volatility: the economy's dependence on foreign capital and its vulnerability to capital flight in times of trouble or when U.S. interest rates start rising, as expected later this year.
At last count, foreign investors held 38.4 percent of the outstanding value of Indonesian government bonds.
"At the margin, the policy can help a little bit. Our longer term view is that rupiah can stabilise, but it won't really be driven by that kind of regulation," said Victor Rodriguez, head of Asia Pacific fixed income at Aberdeen Asset Management Asia.