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A typical 7kW home EV charger draws 32 amps continuously while charging an EV. That is a significant new electrical load, equivalent to running a high power electric shower for several hours each evening. Adding the charger to an existing consumer unit is technically straightforward in principle: a new circuit, a new MCB or RCBO, a new cable to the charger location. In practice, many older Aberdeenshire consumer units cannot safely accommodate the new circuit without modification or replacement. This guide explains when an upgrade is needed before EV charger installation, when the existing unit can stay, and how the two projects fit together.
The simple test: can my consumer unit accept a new 32A circuit?
Three conditions need to be met for the existing consumer unit to accommodate a 7kW EV charger circuit:
- Spare way available: The unit must have at least one spare way (an empty slot) to fit the new MCB or RCBO for the EV charger circuit.
- Adequate spare capacity: The supply to the property must have headroom for the additional 32A continuous load. For a typical Aberdeenshire 80A or 100A single phase supply, this is generally available, but it depends on the existing peak load.
- Compatible RCD protection: The EV charger circuit needs Type A or Type B RCD protection (depending on the charger model). The existing consumer unit must support this either at the unit level or through the RCBO at the new circuit.
If all three conditions are met, no consumer unit upgrade is needed. The EV charger circuit can be added directly to the existing unit. If any of the three conditions fails, a consumer unit upgrade is required either before or as part of the EV charger installation.
When does the existing consumer unit need replacing?
No spare ways available
An existing 6 way unit fully populated with circuits has no spare way for the EV charger circuit. The options are: replace the unit with a larger one, or install a separate sub board next to the existing unit specifically for the EV charger. For most Aberdeenshire homes, replacing the unit is the cleaner solution and provides a long term home for any future circuit additions.
Older unit without RCD protection
EV charger circuits require RCD protection. If the existing consumer unit has rewireable fuses or is an older split load unit without RCD coverage, the EV charger circuit cannot be safely added. The unit needs upgrading to one that provides the required protection.
Existing unit lacks Type A RCD protection
Modern EV chargers can produce DC residual currents that older Type AC RCDs cannot detect. The Wiring Regulations require Type A or Type B RCD protection on EV charger circuits. Older consumer units fitted with Type AC RCDs need either an upgrade to Type A protection at the unit level or a Type A RCBO on the EV charger circuit specifically.
Older unit fitted with rewireable fuses
Rewireable fuses do not provide the speed of disconnection required for safe EV charger operation. Replacement of the unit is mandatory before any EV charger circuit can be installed.
Inadequate supply rating
For a property with an older 60A or 80A supply, a 32A EV charger circuit may push the peak load beyond the supply rating, particularly during a fast charge while the household is using a shower, oven, or other major appliances. Either the supply needs upgrading by SSEN or the EV charger needs to be a load managing model that limits its draw to keep the total load within the supply rating.
When can the existing consumer unit stay?
For many Aberdeenshire homes, the existing unit is fine for an EV charger addition. The conditions that allow the existing unit to stay:
- The unit was installed in the last 10 to 15 years.
- The unit provides comprehensive RCD protection on socket and bathroom circuits.
- The unit has at least one spare way for the new EV charger circuit.
- The supply has adequate headroom for the additional 32A continuous load.
- The unit accepts Type A RCDs or RCBOs (or already has them fitted).
Where these conditions are met, the EV charger installation is a single project that adds the new circuit to the existing unit. Cost: the standard EV charger installation price (typically £900 to £1,500 fully installed including the charger itself, less the OZEV grant where eligible) without the additional consumer unit upgrade cost.
Combined cost: consumer unit upgrade plus EV charger installation
For Aberdeenshire homes that need both:
- Standard consumer unit upgrade: £550 to £800 for a typical 3 bedroom home with a 10 way unit.
- 7kW EV charger installation: £900 to £1,500 fully installed for a Zappi or similar smart charger, before OZEV grant deduction.
- OZEV grant where eligible: up to £500 deducted from the EV charger cost.
- Combined project cost: approximately £1,000 to £1,550 net of OZEV grant.
Combining the two projects into a single visit saves on call out, scaffold (where roof access is needed), and survey costs compared with two separate projects. Faithful Spark provides a coordinated quote for both elements where the EV charger requires a consumer unit upgrade. For more on EV charger installation, see our companion guide on EV charger installation in Aberdeen.
Sub board alternative: when it makes sense
An alternative to replacing the entire consumer unit is to install a small dedicated sub board next to the existing consumer unit, specifically for the EV charger circuit. The sub board has its own RCD or RCBO with the appropriate Type A or Type B protection.
Sub boards make sense when:
- The existing consumer unit is otherwise in good condition with comprehensive RCD protection but simply has no spare way.
- The homeowner wants to defer the full consumer unit replacement to a later date.
- Cost minimisation is the priority.
The sub board cost is typically £200 to £400 above the standard EV charger installation price, less than a full consumer unit replacement. The downside is that the existing unit’s limitations remain, and a future consumer unit replacement will be a separate project.
Load management to avoid supply upgrades
For Aberdeenshire homes with limited supply capacity (older 60A or 80A supplies), modern smart EV chargers offer load management that automatically limits charger draw based on the household’s total load. The myenergi Zappi, Ohme Home Pro, and other current generation smart chargers all support some form of load management.
Load management lets you avoid upgrading the supply by ensuring the EV charger always operates within the available headroom. If you are running the oven, shower, and kettle simultaneously, the charger temporarily reduces its draw or pauses charging. When the household load drops, the charger resumes full power. The total monthly charge time is slightly longer, but no supply upgrade is needed.
For most Aberdeenshire homes with overnight EV charging, load management is sufficient because most of the charging happens during off peak hours when household demand is low.
Other electrical considerations for EV charger installation
Beyond the consumer unit itself, several other elements may need attention:
- Earthing arrangement: EV charger installations have specific earthing requirements that may go beyond the existing property earth. PME supplies (most Aberdeen city properties) require an earth electrode at the charger location for some configurations.
- Cable specification: The cable from the consumer unit to the charger must be sized for 32A continuous load over the full route length. Long runs may need a heavier gauge.
- Cable routing: External cable runs need appropriate weatherproof installation. Faithful Spark identifies the best route during survey.
- OZEV grant eligibility: Some homeowners qualify for the OZEV domestic chargepoint grant of up to £500 toward the charger cost. Eligibility depends on property type and tenure.
- Smart meter requirement: Some grant or tariff programmes require a smart meter. If you do not yet have one, the supplier arranges installation.
Frequently asked questions
My existing unit looks modern. Why might it still need upgrading?
The most common reason is the RCD type. Many consumer units installed before 2019 have Type AC RCDs, which do not detect the DC residual currents some EV chargers can produce. The Wiring Regulations now require Type A or Type B RCD protection on EV charger circuits. The unit may otherwise be in perfect condition; only the RCD type matters for EV charger compatibility.
Can I add a Type A RCBO to my existing unit instead of replacing the whole thing?
Often yes. If the existing unit accepts the brand of RCBO that provides Type A protection on the new EV charger circuit, this is the standard route. Faithful Spark identifies whether the unit supports this at survey.
Will the OZEV grant apply if I also need a consumer unit upgrade?
The OZEV domestic chargepoint grant covers the charger itself, not the consumer unit. The consumer unit upgrade is a separate cost. The grant is still applied to the charger element regardless of whether other electrical work is being done at the same time.
Can I install the EV charger first and upgrade the consumer unit later?
For most installations, no. The EV charger circuit must be safely installed at the time of installation, which means the consumer unit must support the circuit at that point. Doing the consumer unit upgrade later as a separate project does not help if the EV charger circuit cannot be safely added in the first place.
Will my landlord pay for the consumer unit upgrade if I am renting?
This depends on the lease terms and the landlord’s agreement. For Scottish private rentals, the landlord is responsible for the fixed installation under the Repairing Standard. Adding an EV charger is an alteration that typically requires landlord consent. Many landlords agree to fund or contribute to the consumer unit upgrade where it brings the property to a higher standard for future tenants. The OZEV grant for landlord rental properties (up to £500 per charge point) makes the financial case more attractive.
Book a combined consumer unit and EV charger survey
Faithful Spark provides combined consumer unit upgrade and EV charger installation projects across Aberdeen and Aberdeenshire as a single coordinated visit. NICEIC certified, OZEV approved, fixed price quotes covering both elements. See our companion guides on consumer unit upgrades in Aberdeen and EV charger installation in Aberdeen for the full picture.
Faithful Spark Electricians. NICEIC approved. OZEV approved. Local Aberdeen team. Consumer unit upgrades, EV charger installation, and Electrical Installation Certificates for Aberdeen, Peterhead, Ellon, Fraserburgh and across Aberdeenshire.
