The escalating US-Iran war has delivered a fresh inflationary shock to Australia through soaring fuel prices, forcing the Reserve Bank of Australia (RBA) to hike its cash rate twice in quick succession and casting doubt on expected interest rate relief for mortgage holders in 2026.

Reserve Bank of Australia
Reserve Bank of Australia

Petrol and diesel prices have climbed sharply since the conflict began on Feb. 28, with national averages for unleaded approaching A$2.20 per litre in many areas and wholesale diesel hitting A$2.45 in some reports. The RBA responded by lifting the official cash rate by 25 basis points in February and again on March 18 to 4.10%, its second consecutive increase. Senior officials have explicitly linked the move to war-driven energy costs that are "making us all poorer" while pushing inflation risks higher.

The direct channel runs through imported refined fuels. Australia imports about 90% of its petrol and diesel needs despite exporting crude oil and LNG. Disruptions in the Strait of Hormuz — through which roughly one-fifth of global oil passes — have tightened supplies and lifted global benchmark prices above US$100 per barrel. This feeds straight into the consumer price index via automotive fuel, a significant CPI component, and indirectly through higher transport costs for goods and services.

RBA Governor Michele Bullock and other officials have warned that sustained high oil prices could add 0.75 to 1.25 percentage points to headline inflation, depending on duration and severity. A senior official noted in recent speeches that the fuel-linked spike may necessitate a more restrictive monetary policy stance to prevent second-round effects, such as rising wage and price expectations.

For the roughly 40% of Australian households with mortgages — many on variable rates — the impact is immediate and painful. Major banks including Commonwealth Bank, NAB and Westpac passed on the March hike in full or in part, increasing variable home loan rates by around 0.25 percentage points. This adds roughly A$50–A$70 per month to repayments on an average-sized mortgage of A$600,000–A$700,000, depending on the lender and remaining term.

Fixed-rate borrowers who locked in lower rates in 2025 are temporarily insulated, but many face refinancing in the coming 12–24 months into a higher-rate environment. Economists from HSBC, AMP and others have revised forecasts, with some now expecting the cash rate to remain at or above 4.10% well into late 2026 or even 2027 if the conflict drags on. Rate cuts that were once anticipated for mid-2026 have been pushed back or removed from forecasts entirely.

The war's influence extends beyond the RBA's cash rate decision. Global bond markets have reacted to heightened inflation risks, pushing Australian government bond yields higher. The 10-year Australian government bond yield has climbed in recent weeks, influencing longer-term fixed mortgage pricing even before any further RBA moves. Lenders have already repriced some fixed-rate products upward, with two- and three-year fixed rates rising by 10–20 basis points or more in some cases.

Beyond direct interest rate effects, the conflict is squeezing household budgets through higher petrol and grocery costs, reducing discretionary spending and confidence. This weakens demand in the housing market at a time when many buyers were already stretched by affordability challenges. Property analysts warn that sustained higher borrowing costs combined with cost-of-living pressures could delay the anticipated recovery in home sales and prices, particularly in outer suburban and regional markets.

Construction costs are also rising as diesel and fuel levies hit material transport and energy-intensive inputs like concrete and plastics. Some builders have introduced emergency surcharges, adding further pressure to new-home prices and potentially slowing supply growth just as more homes are needed.

The RBA faces a difficult balancing act. While the central bank must respond to the inflationary impulse from energy prices, overly aggressive tightening risks tipping the economy into weaker growth or even recession, especially with global uncertainty weighing on business and consumer sentiment. Recent CPI data showed headline inflation easing slightly to 3.7% in February before the full war effects were felt, but underlying pressures remain and the oil shock has not yet fully fed through.

Treasurer Jim Chalmers has described the economic consequences as "very substantial," noting they will shape the May budget. The government has released some strategic fuel reserves and relaxed quality standards to boost local refining, but these are short-term measures. Longer-term fuel security — including greater domestic refining capacity or accelerated transition to alternatives — remains a policy focus.

For variable-rate mortgage holders, every 25-basis-point increase adds meaningful cost. On a A$650,000 loan, it equates to roughly A$1,625 extra per year. With two hikes already delivered and more possible, the cumulative effect could reach several thousand dollars annually for many households.

Economists stress that Australia's position as a net energy exporter provides some offset through higher LNG and coal revenues, but the refined fuel import dependence creates an asymmetric hit to households. Calls for targeted relief, such as temporary fuel excise cuts or cost-of-living payments, have grown louder.

The outlook remains fluid. A swift resolution to the conflict could allow oil prices to moderate, easing pressure on inflation and potentially reopening the door to RBA rate cuts later in 2026. A prolonged disruption, however, risks embedding higher inflation expectations and keeping borrowing costs elevated, prolonging pain for mortgage holders and cooling the housing market further.

As the war continues without clear end in sight, Australian borrowers are bracing for higher repayments and delayed relief. The Iran conflict has reminded policymakers and households alike how quickly distant geopolitical events can translate into higher costs at the petrol pump and the mortgage table.