Can my electric car power my house during a power cut?

The short answer: yes, with a compatible backup system

A large electric-vehicle battery can hold several times the energy of a typical home battery. If your car and installation support vehicle-to-home backup, that energy could keep essential circuits running much longer during an outage.

However, a car that can charge in both directions, power a kettle or sell electricity to the grid is not automatically a car that can keep your house running when the grid fails. The complete arrangement matters.

V2L, V2H and V2G: three different promises

For example, Hyundai describes the IONIQ 5's V2L function as providing up to 3.6 kW for appliances. That is a useful facility, but it is not evidence of an approved UK whole-home backup installation. Hyundai's explanation.

Do not connect an appliance outlet to a household wall socket to energise the house. Fixed-wiring backup needs a properly designed installation. Ask a qualified installer about any proposed use of V2L with dedicated changeover equipment.

Could an EV battery keep the lights on for days?

Yes, the capacity maths can be encouraging. Start with the car's usable battery capacity, deduct the charge you need to keep for driving, then allow for conversion losses. Divide the remaining household energy by the electricity you expect to use each day.

Starting charge matters enormously. The same 75 kWh battery beginning at 80%, with a 20% reserve and 90% efficiency, leaves 40.5 kWh for the house. Beginning at 60% leaves 27 kWh. If the car is away when the power fails, its energy is away too.

Energy capacity is not appliance power

kWh tells you how much energy is stored. kW tells you how much power can be delivered at once. A large battery still cannot supply appliances beyond the backup system's output limit. A 9 kW shower, for instance, exceeds a 3.6 kW appliance outlet regardless of battery size.

For emergency use, plan around lights, refrigeration, communications and suitable heating controls first. Check starting surges and whether the system can support the boiler or heat pump. “Five days of essentials” and “five days of unrestricted normal living” are very different proposals.

Which vehicles and battery systems support it?

The evidence needs three separate checks: what the vehicle supports, what the equipment can do, and whether that exact combination is available and approved for your UK installation. The examples below are not a universal compatibility list.

Manufacturer-confirmed capabilities, overseas products and independent field tests are different kinds of evidence. A successful demonstration is valuable, but does not settle UK warranty support, extended runtime or what happens after a vehicle software update.

Why Sigenergy is interesting—and why the caveats matter

Its DC charging module places the car within an integrated home-energy architecture rather than treating it purely as a charging load. That makes it relevant to this conversation. However, its field-test qualification can be met by a discharge lasting 15 minutes, or by specified energy or state-of-charge thresholds. A listed test does not demonstrate several days of unattended backup.

Ask for evidence specific to the car you own or intend to buy, including what has been tested during a real loss of grid supply. Do not turn a brand appearing in a field-test database into a blanket promise for every car that brand sells.

Does an existing home battery make the car compatible?

No. An ordinary AC EV charger is generally an electricity-consuming device. A home battery, a hybrid inverter or a backup gateway cannot make that charger bidirectional or add a discharge feature to the vehicle.

If you already have a battery system, ask whether the proposed vehicle equipment has a documented integration with it. Establish who controls the two batteries, how their reserves work, what happens during outages and which components remain under warranty. Brand names alone cannot answer those questions.

Why a gateway isolation switch is only part of the answer

During an outage, your home must be safely separated from the public network before it can be energised locally. The installation also needs equipment that can establish and control the home's electrical supply without relying on the grid.

A proper design addresses switching, protection, earthing, phase configuration, appliance starting currents and the circuits you want backed up. The IET explains why island-mode earthing and protection require a deliberate design. Your installer must also establish applicable DNO connection and export requirements; see the Energy Networks Association connection guidance. See our G98 and G99 guide.

Can solar top up the car during a power cut?

Potentially, if the solar equipment remains operational within the designed backup system and can charge the vehicle in that operating mode. Many grid-connected solar systems switch off when the network fails. Do not assume existing panels will keep generating simply because a car battery has been connected.

Ask whether the system can restart after its available batteries have been depleted, how it behaves if the car disconnects, and whether internet access is required for critical backup functions. A demonstration with everything already running does not answer every restart scenario.

For the broader solar and stationary-battery explanation, read what happens to solar panels during a power cut.

Before buying a car or battery system for home backup

Make backup a written specification before choosing the equipment. “V2H ready” is a starting point for questions, rather than a complete answer.

1. Identify the vehicle precisely. Model year, UK specification, connector, battery variant, firmware and activation requirements. Is discharge officially supported by its manufacturer for the proposed arrangement?
2. Specify the whole equipment chain. Bidirectional charger or DC module, controller, inverter, gateway and any required stationary battery. Ask for the compatibility documents and the party responsible for commissioning.
3. Separate home use from outage backup. Does it work with the grid absent? Is changeover automatic? What interruption should you expect? Which circuits remain live?
4. Check output as well as capacity. Continuous and surge power, single- or three-phase operation, per-phase limits and simultaneous appliance use. Get clear answers for your heating and cooking equipment.
5. Protect your driving reserve. Set a realistic minimum charge. Consider when the car is usually away and whether a stationary battery should cover that absence.
6. Request the warranty position. Get written clarification for both car and energy equipment. Confirm permitted discharge use, any throughput conditions, support after software changes and who pays for diagnosis or remedial work.
7. Confirm permissions and installation costs. Ask about DNO requirements, electrical upgrades, extra equipment, subscriptions and servicing. Compare the complete installed price with stationary-battery backup.
8. Commission the scenario you are buying. Have the installer demonstrate grid-loss operation, reconnection, reserve behaviour and restart capability. Obtain operating instructions and a clear support contact.

Compare home battery warranties and learn how to compare complete solar quotations before making a commitment.

EV backup or a bigger home battery?

The EV offers substantial potential capacity, but it has to be home, plugged in and compatible. A stationary battery is available independently of your driving schedule, although its backup capability also depends on its inverter, switching and installation.

For some households, a stationary battery covering everyday demand and essential backup, with a compatible car extending duration, could be an attractive combination. For others, a simpler stationary system or V2L for a few portable appliances may meet the actual need more economically.

Quick answers

Sources and scope

This guide uses manufacturer documentation and current supplier statements linked beside the relevant claims. The Volkswagen announcement is historical; Kia's cited V2H evidence is for the US; Sigenergy's field tests are independent of vehicle manufacturers. These distinctions are deliberate.

Availability, firmware and supported combinations change. This review does not certify any installation, independently test the equipment or establish an exhaustive UK vehicle compatibility list. Ask for up-to-date written evidence for your own purchase.

• Nissan UK: LEAF charge/discharge manual
• Volkswagen: bidirectional charging announcement, 6 December 2023
• Kia US: vehicle-to-home requirements
• Wallbox UK: Quasar 2
• Hyundai: IONIQ 5 V2L
• Octopus: Power Pack eligibility
• Sigenergy: DC charger and field-test qualifications
• Indra: current bidirectional product status