How do EV chargers work when there is a power cut?

During a power cut, standard home EV chargers will immediately stop functioning to comply with UK safety regulations, as they rely on grid electricity. However, backup options exist to maintain charging capability, primarily through battery storage systems or emergency power supplies (EPS).

Backup Solutions for EV Charging During Outages

Battery Storage Systems

• How they work: Solar batteries (e.g., Tesla Powerwall, GivEnergy) with EPS functionality store energy from solar panels or off-peak grid electricity. During a power cut, they disconnect from the grid and power designated circuits, including EV chargers if included in the backup setup.
• UK-specific considerations:
• Most solar inverters require additional hardware (e.g., automatic contactors) to activate EPS mode.
• Only advanced systems like Tesla Powerwall allow solar generation during a power cut, while others rely solely on stored battery energy.

Manual Changeover Systems

• Level 3 Backup: Involves rerouting the home’s main power supply through a battery system. High-power devices (including EV chargers) must be manually switched off before engaging the backup to avoid overloading the battery.
• Practical advice: Use timers or smart chargers to schedule charging during off-peak hours when the battery is fully charged, maximizing backup duration.

Real-World Applications in the UK

• ev.energy’s Powercast: Partners with UK Power Networks to notify EV drivers of impending power cuts via mobile alerts, enabling proactive charging before outages.
• Case study: A homeowner with a PowerBanx battery system can manually prioritize circuits during a power cut, keeping essentials (e.g., fridges, lights) running while pausing EV charging until grid power resumes.

Key Considerations

• Pros:
• Energy resilience: Maintain critical power for EVs and household essentials.
• Cost savings: Charge EVs during off-peak periods using stored battery energy.
• Cons:
• Upfront costs: EPS-compatible systems require additional hardware and installation (£1,000–£5,000+).
• Limitations: Standard solar arrays shut down during outages unless paired with advanced inverters.

Common Mistakes to Avoid

1. Assuming automatic backup: Most solar/battery systems need pre-installed EPS hardware—confirm this during installation.
2. Overloading circuits: Attempting to run EV chargers + high-power devices (e.g., showers) simultaneously on backup power risks tripping the system.
3. Ignoring notifications: Failing to act on power cut alerts (e.g., via UK Power Networks) reduces backup effectiveness.

Recent UK Developments (2023–2024)

• Grid-scale batteries: Increased adoption helps stabilize the grid during outages, indirectly improving EV charging reliability.
• Smart charging mandates: New UK regulations encourage bidirectional charging systems, which could enhance future backup options.