Installing an electric vehicle charger and an air-source heat pump can significantly reduce your home's reliance on fossil fuels. However, both are substantial electrical loads, and adding them to an older Redhill property needs more thought than simply finding a spare way in the consumer unit.
The key question is not only whether the charger and heat pump can operate individually. It is whether your incoming supply, consumer unit and existing household demand can safely accommodate them together.
The basic electricity calculation
Most UK homes have a single-phase supply with a main cut-out fuse rated at approximately 60A, 80A or 100A. At around 230V, that equates to roughly:
- 60A: 13.8kVA
- 80A: 18.4kVA
- 100A: 23kVA
A typical home EV charger rated at 7kW draws around 32A continuously while charging. That is a significant addition to the property's demand and should not be treated like an occasional small appliance.
A domestic air-source heat pump may draw approximately 10–16A while running, depending on its size, efficiency and operating conditions. However, its electrical demand can change. Compressor starting current, defrost cycles, pumps, controls and an immersion or backup heater can all increase demand temporarily or for longer periods.
You also need to consider:
- An electric shower, which may draw 40A or more
- An oven and hob
- A tumble dryer or washing machine
- An immersion heater or thermal store
- Existing electric heating
- Normal background loads throughout the home
This is where diversity comes into the calculation. Diversity recognises that every appliance will not necessarily operate at full power at precisely the same moment. However, it does not mean that you can simply add up all circuit breaker ratings and ignore the result.
The main fuse rating is a maximum protective limit, not a promise that the property can run that current continuously without consideration. A 100A fuse does not mean that 100A of uninterrupted load is automatically available for the EV charger, heat pump and every other appliance.
Three realistic outcomes
1. Both systems fit comfortably
This is most likely where the property has a 100A supply, the heat pump has a modest electrical input, and the home does not regularly use several other high-demand appliances at the same time.
For example, the EV may charge overnight while the heat pump is running at a relatively low output. Cooking, showering and laundry can then be spread across the day.
This does not remove the need for a proper maximum-demand assessment, but it may mean that a standard 7kW charger and dedicated heat-pump circuit can be installed without a supply upgrade.
2. Both systems fit with load management
This is a common and practical solution, particularly on an 80A supply or where the household has an electric shower, immersion heater or other substantial loads.
The EV charger remains capable of delivering up to 7kW, but it reduces its output when the property's total demand rises. Charging may slow down temporarily rather than continuing at full power regardless of what else is operating.
In practice, most vehicles are parked for several hours overnight. A charger that briefly reduces its output while a heat pump or cooker is running can still provide a full overnight charge.
3. The electricity supply becomes the bottleneck
A 60A supply can become restrictive when a 32A EV charger is combined with a heat pump, electric shower, immersion heater and normal household demand.
Possible solutions include:
- Applying to the Distribution Network Operator (DNO) for a larger supply
- Using a charger with properly designed dynamic load management
- Scheduling certain loads at different times
- Selecting a lower charging rate
- Considering a three-phase upgrade where demand is particularly high
The correct answer depends on the actual supply rating, cable arrangements, earthing system, heat-pump design and the household's likely usage.
What dynamic load balancing actually does
Dynamic load management, sometimes called dynamic load balancing, normally uses a CT clamp installed around the incoming supply conductors. The clamp measures how much current the property is drawing.
A controller then communicates with the EV charger. If the heat pump, oven or shower increases total demand, the charger automatically throttles back. When demand falls, charging can increase again.
This is different from:
- Built-in charger load balancing: the charger may contain the control hardware, but it still needs to be installed and configured correctly.
- Solar diversion: systems such as a Zappi's Eco modes use surplus solar generation to charge the vehicle. That is about using available generation, not necessarily protecting a restricted incoming supply.
- Timed charging: a schedule avoids certain hours but cannot respond to an unexpected shower, oven or heat-pump surge.
A CT-based system must be suitable for the proposed installation and configured around an agreed maximum demand. It should not be added as an afterthought without checking the DNO requirements and manufacturer's instructions.
Heat-pump details that are easy to overlook
The heat pump itself is not always a steady, predictable load.
At start-up, the compressor can create an inrush current. During cold weather, the system may enter a defrost cycle. Some installations also include an immersion heater or electric backup heater, which can add a much larger demand than the heat pump compressor alone.
The MCS heat-pump installer will often specify a dedicated circuit from the consumer unit, with its own protective device and RCD or RCBO arrangement. This allows the system to be isolated, tested and protected independently.
The EV charger also needs its own dedicated circuit. Under BS 7671 Section 722, the installation requires appropriate residual-current protection. The correct arrangement depends on the charger's built-in DC residual-current detection and the manufacturer's instructions. In many cases, a Type A arrangement is suitable where the charger provides the required DC protection; Type AC protection is not appropriate for a modern EV charging circuit.
The consumer unit may also need:
- Enough spare ways for separate EV and heat-pump circuits
- Suitable RCD or RCBO protection
- Surge protective devices in accordance with the current 18th Edition requirements
- Correct main bonding and earthing
- A suitable enclosure and circuit identification
A consumer-unit replacement is sometimes necessary, but it is often only one part of the design. Cable routes, supply capacity and DNO approval can be more significant than the board itself.
DNO notification, prior approval and G100
A single EV chargepoint installation may follow a notification route, depending on its rating, the supply and the relevant DNO process. Adding a heat pump changes the assessment.
Where two high-demand low-carbon technologies are being connected at the same property, it is sensible to treat the work as requiring DNO review or prior approval, rather than assuming that a simple post-installation notification is sufficient. The DNO may require:
- Details of the existing main fuse and maximum demand
- The EV charger rating
- The heat pump's electrical input and backup-heater rating
- Details of the load-management equipment
- A supply upgrade or connection application
Lead times vary. A straightforward notification may be relatively quick, while a supply upgrade, service-head replacement or network reinforcement can take considerably longer.
It is also important not to confuse G100 with every form of EV load balancing. ENA EREC G100 is principally associated with export-limiting schemes, such as solar PV or battery systems. If your home also has generation or storage, the designer may need to consider G98, G99 or G100 requirements as well as import capacity. The relevant DNO will confirm the required route.
What about solar panels and a battery?
Solar PV does not remove the need to assess maximum demand, but it may reduce imported power while the sun is generating. A battery can also help by discharging during periods when the heat pump, charger and household loads overlap.
That does not mean the battery should be treated as a substitute for suitable protection or DNO approval. It is one part of the overall energy design, particularly where the battery system includes export limitation or a larger inverter.
Local considerations in Redhill and Surrey
Homes in Redhill, Reigate, Earlswood, Merstham, Meadvale, Nutfield, Salfords, Linkfield and Whitebushes can vary considerably in age and electrical arrangement.
Older terraces may have smaller service heads, limited consumer-unit space or looped supplies. Homes with off-street parking may also need longer cable routes to a driveway or detached garage.
Properties close to the Surrey Hills or Green Belt may have separate planning considerations for external equipment, although planning permission and electrical capacity are different questions. The sensible approach is to assess both the location of the charger and heat-pump unit, and the electrical infrastructure, before ordering equipment.
A standard EV charger installation is typically around £895–£1,250 supplied and fitted, with a consumer-unit upgrade adding roughly £200–£500 where required. Combined EV-charger-and-heat-pump projects need a site-specific quote because DNO applications, supply upgrades and longer cable routes can change the overall cost significantly. That is why a free survey is more useful than relying on a standard online price.
The best order of work
For a home planning both technologies, we recommend:
- Survey the existing installation first, including the cut-out rating, consumer unit, earthing and available ways.
- Confirm the proposed heat-pump electrical demand, including immersion or backup heating.
- Apply to the DNO early if the combined demand may require prior approval or a supply upgrade.
- Choose an EV charger that supports suitable CT-based load management.
- Coordinate the heat-pump and charger installers, rather than allowing each contractor to design in isolation.
- Test, certify and commission the complete installation once both systems are connected.
As a NICEIC Approved Contractor, ADS Electrical can coordinate with other trades and help ensure the electrical work is designed as one connected project.
Frequently asked questions
Can I run a 7kW EV charger and heat pump on a 60A supply?
It may be possible with carefully designed load management, but it is often restrictive once electric showers, ovens and backup heaters are included. A supply upgrade or reduced charging rate may be more appropriate.
Is an 80A supply enough?
Sometimes. An 80A supply may support both systems when dynamic load balancing prevents the total demand from exceeding the agreed limit. The result depends on the heat pump and the rest of the home.
Do I need a 100A supply?
Not automatically, but 100A generally gives more practical headroom for a typical 7kW charger, heat pump and domestic loads. It still requires a proper assessment.
Does load balancing slow down my car charging?
It can temporarily reduce or pause charging when other demand rises. Once demand falls, the charger can increase its output again. For overnight charging, this is often a workable compromise.
Who should assess the installation?
Use a suitably qualified electrician familiar with EV charging, heat-pump supplies, BS 7671 Section 722 and DNO requirements. If you need an electric car charger installers Surrey team, ADS Electrical offers a free survey and free quotes within 24 hours.
For local EV charging solutions Redhill, contact ADS Electrical to discuss the supply before committing to equipment. We provide clear advice, coordinate with other installers and carry out work to the required standards. For urgent electrical problems, our 24-hour emergency call-out line is 07870 554498.