TNB Alerts EV Owners on Single-Phase Charging Risks

Most Proton e.MAS and potentially the Perodua QV-E will come with a 7kW home charger complimentary

Tenaga Nasional Berhad (TNB) has issued an advisory to MyZEVA and MYEVOC following a rise in blown cut-out fuses and burned fuse casings at single-phase residential properties, with many cases linked to home EV charging.

According to TNB, investigations showed that overloads frequently occurred when EV chargers were operated at full power on single-phase connections. The utility is urging homeowners and service providers to verify supply capacity before installing or using EV charging equipment.

TNB explained that a typical single-phase home with an existing 5 kW load cannot safely support a 7 kW charger unless the home is upgraded to three-phase. The upgrade allows the electrical system to accommodate household demand alongside EV charging without overloading.

The utility also reminded users to follow guidelines outlined in the Electricity Supply Application Handbook (ESAH) and the Energy Commission’s Guide on Electric Vehicle Charging System to ensure compliant and safe installations.

MYEVOC president Datuk Shahrol said the situation is serious, with incidents already involving blown fuses, melted enclosures and minor fire damage. He urged users charging at 7 kW to follow TNB’s advice to upgrade to a three-phase supply, and recommended installing a smoke detector for added peace of mind and safety.

For homes that remain on single-phase, he advises users to manually reduce charging current on their vehicle, lowering it from 32A to around 20A — providing roughly 4 kW of charging power, which is adequate for overnight charging while keeping loads safer. 

Out of box, factory setting reads 32A

EV users were also cautioned against the dangerous practice of replacing the standard 32A fuse with a 63A fuse, which may prevent trips but removes a critical safety barrier, exposing wiring to excessive current.

As EV adoption continues to climb rapidly — driven by the arrival of more affordable models such as the Proton e.MAS 5 and 7, and the upcoming Perodua QV-E — TNB noted that many new owners are also receiving complimentary 7 kW home chargers from manufacturers. 

Throttle it down to 20A or lower to reduce load stress for a peace of mind

While these chargers add convenience, they also increase the likelihood of homeowners installing or using them on insufficient single-phase supplies, further underscoring the need for proper load assessment and safe installation practices.

Since most home charging occurs overnight while occupants are asleep, maintaining conservative electrical loads is crucial to avoid stressing older wiring and preventing fuse failures. 

Upgrading to three-phase remains the ideal long-term solution for consistent high-power charging, but reducing charging current offers an immediate, practical safeguard for households that remain on single-phase.