If the past six weeks have felt like the world’s energy problems suddenly showed up in your everyday spending, that’s because they did, first at the bowser, then in freight and delivery fees, and now (more quietly) in the interest-rate expectations that banks use to price loans.
What matters most for households and businesses right now: the global fuel supply disruption tied to the conflict and the extent to which it turns into “second-round” inflation (price rises spreading beyond fuel itself).
This framing matters because it’s the bridge between geopolitics and your loan rate. A fuel shock on its own hurts, but central banks typically don’t lift interest rates just because petrol is expensive for a month. They tighten when fuel costs start changing the pricing behaviour of the whole economy because then inflation becomes harder to bring back down.
Strait of Hormuz is the economic trip‑wire
The Strait of Hormuz as the critical fault line for the global economy, because it is a narrow chokepoint for oil flows and other energy shipments.
Independent energy data backs up why this one waterway matters so much. The U.S. Energy Information Administration estimates that in 2024 oil flows through the strait averaged about 20 million barrels per day or around 20% of global petroleum liquids consumption.
As at 13 April 2026, the key point for borrowers isn’t the politics it’s the plumbing:
- Shipping through Hormuz has been severely curtailed. Reuters reported on 9 April that traffic was well below 10% of normal volumes, with only a handful of ships transiting compared with roughly 140 normally.
- Reuters also reported on 13 April that the US announced a naval blockade applying to shipping in and out of Iranian ports, tightening oil supply further while the broader strait remained highly disrupted.
Those disruptions quickly showed up in fuel benchmarks and Australian pump prices. The Australian Competition and Consumer Commission (ACCC) documented a sharp jump between 20 February and 11 March: Brent crude rose (weekly average) from about US$73 to US$91 per barrel, while key refined fuel benchmarks rose even more. Retail prices followed, with large increases in average unleaded petrol and diesel across the capital cities over the same period.
The “why” for loan pricing is straightforward: fuel is an input into almost everything from transport, construction materials, food distribution, “last mile” delivery, and (when supply chains are strained) the availability and timing of stock. When fuel and freight get expensive enough, they stop being a household-only problem and become a business-wide cost shock.
When fuel jumps, the real risk is second‑round inflation
For borrowers, it is not simply “fuel is up”. Australia was already seeing fast and broad “pass-through” from fuel into other prices, and that this behaviour is exactly what can force the central bank’s hand.
“Second-round effects” sounds technical, but it just means this:
- First-round: petrol and diesel cost more.
- Second-round: businesses start raising prices for many other goods and services because their fuel, freight, packaging, inputs, or operating costs have risen and sometimes because they believe customers will accept it.
- Over time: higher energy costs can also lift inflation expectations (“everything is getting more expensive”), which itself can affect pricing decisions.
This is not just theory. A detailed Federal Reserve research note finds that oil price increases can pass through to inflation directly and via second-round effects through broader production and transportation costs and through the expectations channel. The International Monetary Fund has also found second-round effects showing up in measures like core inflation and expected inflation, with responses that can be gradual (rather than immediate) but still meaningful for monetary policy.
Westpac’s point, as at mid-April, is that the pass-through in Australia appeared unusually quick. The bank’s more hawkish rate outlook to “early signs of strong second-round pass-through from fuel to other prices.”
Why does this matter for financing?
Because lenders care less about one-off price spikes and more about persistent inflation, persistent inflation is what changes interest rates, borrowing capacity, and default risk assumptions.
How Reserve Bank of Australia policy turns inflation into loan rates
The RBA’s inflation target is 2–3% annual CPI inflation over time, and the Bank sets monetary policy with the aim of returning inflation to the midpoint of that target.
The most recent official inflation read available as at 13 April 2026 was the February monthly CPI indicator. It showed CPI inflation at 3.7% over the year to February (with trimmed mean inflation at 3.3%). Importantly, this reading largely predates the late‑February conflict escalation and the early‑March fuel surge, meaning it does not fully capture the shock that Westpac is worried will propagate through prices.
Against that backdrop, the RBA has already been tightening:
- The cash rate target was lifted to 3.85% effective 4 February 2026.
- It was lifted again to 4.10% effective 18 March 2026.
The transmission into household and business finances is not subtle: the RBA explains that policy affects economic activity partly through a “cash-flow channel”, interest rates change interest repayments on debt, especially for variable-rate mortgage holders.
If second-round inflation becomes embedded, the RBA will feel it needs to do more demand-crimping than it otherwise would. The RBA is likely to respond to the observed pricing behaviour by tightening more than would have been needed if fuel price rises had not spread into broader prices.
That’s the core “loans impact” message: not “petrol is expensive”, but “petrol is pushing the expected peak in interest rates higher.”
How loan pricing actually moves: funding costs, market rates and bank behaviour
A common misconception is that banks simply “follow the RBA”. In reality, loan rates are anchored by:
- the cash rate (a benchmark for the overall level of interest rates), and
- banks’ funding costs (what banks must pay for deposits and wholesale funding), plus
- margins for credit risk, capital requirements and competition.
The RBA notes deposits are around two‑thirds of Australian banks’ funding, with bonds and other wholesale debt around a third. Funding costs don’t move uniformly: market reference rates tend to respond quickly, while deposit rates can move by less, or with a lag, because banks have discretion and because competition for deposits varies.
A particularly important detail for borrowers is that many parts of bank funding, and many business loan contracts are linked to short‑term wholesale rates such as the bank bill swap rate (BBSW). The RBA has explained that BBSW is heavily influenced by the cash rate, including expectations of future changes, and it matters because it is a reference rate for banks’ short-term wholesale debt and for hedging fixed-rate liabilities.
This is why expectations move loan rates:
- When markets decide the “likely peak” cash rate is higher, BBSW and swaps can rise even before the RBA actually changes the policy rate.
- Banks that fund or hedge off those rates then face higher forward costs, which encourages higher fixed rates, tougher pricing, or both.
You can see the immediate pass-through in how lenders announced changes after the March move. Macquarie Bank publicly stated it would lift variable home loan reference rates by 0.25 percentage points following the RBA’s March decision (with a short implementation lag).
For households, another practical wrinkle is that pass-through can be uneven across time because of the mix of fixed and variable loans. The RBA’s work on mortgage pass-through shows that, in earlier tightening episodes, the average rate paid by outstanding mortgage borrowers did not always rise one‑for‑one immediately, especially when many borrowers were on fixed rates and repricing happened later. The lesson is not “rates won’t rise”; it’s that repricing can arrive in waves.
What this means for common borrowing situations
The clearest way to think about the Westpac view is this: a fuel supply shock becomes a loan shock if it changes the expected interest-rate path. Westpac is explicitly saying that second-round inflation risks have lifted that expected path.
If you have a variable-rate home loan
Variable mortgage rates are the most direct transmission channel. When lenders pass through cash-rate increases (and when their funding costs rise), repayments rise quickly.
A simple illustration (not a forecast) helps show what’s at stake:
- On a $600,000 loan over 30 years, a 0.25 percentage point rise in the interest rate increases monthly repayments by roughly $100 (depending on the starting rate and remaining term).
- If rates rose by 0.75 percentage points in total, the monthly increase could be roughly $300 on the same loan (again, highly dependent on the starting point).
Those numbers are just maths. The economic point is what Westpac is warning about: if second-round inflation persists, the “higher for longer” rate environment becomes more plausible, and that pushes the risk onto variable-rate borrowers first.
If you’re fixed especially if the fixed period ends soon
Fixed-rate borrowers can be insulated until they refinance or roll off the fixed term. The RBA’s analysis shows that repricing waves matter: when fixed loans expire, borrowers can move from older low rates to prevailing higher rates, lifting the average mortgage rate across the system over time.
In a world where Westpac expects a higher peak cash rate than previously assumed, the risk is not just “your fixed rate ends”, it’s “your refinance rate may embed a more hawkish policy outlook than you budgeted for.”
If you’re applying for a new mortgage
New borrowers get hit in two ways:
First, advertised rates may be higher when banks reprice off funding markets and expectations.
Second, borrowing capacity can fall even faster than repayments rise because of the serviceability test. The Australian Prudential Regulation Authority (APRA) has kept the mortgage serviceability buffer at 3 percentage points. In plain terms: lenders assess whether you can still repay if rates are about 3% higher than your loan rate at origination.
So if market pricing (and Westpac’s view) shifts toward a higher peak, that can translate into lower maximum loan sizes sometimes before the household has even seen a full pass-through in actual repayments.
If you run a small business and borrow on variable rates
For many businesses, the financing risk is a double squeeze:
- Costs rise (fuel, freight, inputs), and some of that is hard to avoid.
- Borrowing costs rise as variable business loans reprice off higher benchmark rates and bank funding costs.
Second-round effects are already showing up in broader pricing behaviour. If that’s right, businesses can face an awkward choice: raise prices (risking demand) or absorb costs (risking margins and cash flow). Either path can affect lending outcomes, credit assessment, covenant headroom, and the appetite of banks to extend additional working capital.
Are widespread defaults likely?
The RBA’s latest detailed household resilience analysis (from its 2025 Financial Stability Review) noted that loan arrears had stabilised around pre‑pandemic levels, with risks concentrated among highly leveraged and lower‑income borrowers. It also emphasised that many mortgagors had liquidity and equity buffers that help absorb higher inflation and interest rates though stress is always more acute for those with thin buffers.
That doesn’t mean “no pain”. It means the stress is likely to be uneven: households close to their borrowing limits and businesses with tight cash conversion cycles tend to feel it first.
What to watch from here, without pretending we know the future
As at 13 April 2026, three indicators matter most for borrowers and anyone arranging finance:
The fuel supply reality on the ground: shipping volumes and effective transit capacity through Hormuz remain severely restricted, and policy actions affecting Iranian shipping add further uncertainty to supply.
Evidence of second-round inflation in everyday prices: the whole Westpac “hawkish” stance hinges on fuel costs spreading into non-fuel pricing behaviour. If businesses keep adding fuel surcharges and raising prices broadly, that strengthens the case for tighter policy.
How lenders reprice even before official moves: because bank funding and hedging are linked to market rates and expectations, fixed rates and borrowing margins can shift on changing assumptions especially when inflation risks feel less “temporary” and more “sticky”.
Put simply: the conflict matters for loans mainly through inflation persistence. If fuel disruptions prove time‑limited and do not embed broader pricing behaviour, the pressure on the expected peak in rates eases. If fuel disruptions continue and second‑round effects intensify, financing stays tighter and more expensive.
