Tesla Software Update Cuts Third-Party Home Backup for EV Owners

A Tesla software update rolling out since October is cutting third-party home-backup discharge within minutes, stranding owners who power their houses from their cars. Reports on the Tesla Motors Club forum, covered by Drive Tesla Canada, describe power stopping after roughly three minutes with a battery management alert, or after 15 to 20 minutes regardless of load. The 2026.38 branch's release notes cite only "security improvements" and minor fixes.

On 12 October, before the update reached him, electrical engineer and Australian Electric Vehicle Association member Mark Purcell ran his Queensland house on about 25 kW drawn from his Model Y through a Sigenergy bidirectional DC charger. The car's battery holds several times the energy of a typical home battery, he noted, and he has already paid for it. Users of EleJoy, Tlyard and Sigenergy equipment are all affected. Tlyard now warns customers that Tesla's 2026 software detects "simulated charging" and may cut the power link. The old Camp Mode and Service Mode workarounds no longer work.

What does the same update deliver elsewhere?

The same 2026.38 branch brought Powershare with Powerwall home backup to owners in the United States and Canada, finally matching Ford, GM and Kia in letting a car back up a house. Australia received nothing equivalent. Tesla Australia says Powershare cannot be retrofitted to existing vehicles, and in that market Powershare is vehicle-to-load only. For every existing Tesla on Australian roads, third-party equipment is the only path to vehicle-to-home power; if the software blocks it, owners lose both options.

What does the warranty actually say?

The Tesla Australia owner's manual states: "Do not use the Battery as a stationary power source. Doing so voids the warranty." Tesla's Australian warranty page is narrower, excluding only damage caused by third-party adaptors or chargers. Australian Consumer Law is narrower still: statutory consumer guarantees cannot be signed away by a manual line. Apple learned this when the Federal Court ordered A$9 million in penalties over the "Error 53" affair, after Apple told customers third-party repairs had cost them their rights.

Why does this matter beyond Tesla?

Australia leads the world in rooftop solar and is subsidising home batteries at scale. Bidirectional charging is how the largest battery most households will ever own — the one parked outside — reaches the home and eventually the grid. That depends on interoperability. If a carmaker can switch off discharge overnight through an over-the-air update the owner cannot roll back, and without disclosure, every bidirectional charger becomes a bet on that carmaker's goodwill. Suppliers lose fleet access and grid operators lose flexibility. The ACCC has already named "denying interoperability" as conduct that can distort competition in digital platform markets.

What happens next?

Purcell has deferred updates on both his Teslas, asked Tesla in writing to hold updates until it confirms discharge will keep working, lodged an ACCC complaint, and asked the Australian Electric Vehicle Association for support. He concedes Tesla may have a genuine safety or engineering reason, and says the company should state it and consider certified partner equipment, discharge limits, or a published interface for charger makers.

His three demands apply beyond Australia: disclose functional changes in plain language before shipping, let owners choose their charger, and set interoperability rules for vehicle discharge as regulators already do for solar inverters. "No owner, in any country, should have to choose between a current car and a working home battery," Purcell wrote. David Waterworth, who helped publish the piece, added: "I am looking forward to the discussions around this topic."

The dispute previews the regulatory fight ahead as vehicle-to-grid product plans meet platform-controlled hardware.