Quick Summary (TL;DR)
For most UK homes, a professionally installed 7–7.4 kW single-phase smart charger is the sensible default. An 11 kW unit can be worthwhile where three-phase supply already exists and the vehicle accepts 11 kW AC; a 22 kW unit makes sense only when the property can supply roughly 32 A on each of three phases, the vehicle can actually accept 22 kW AC, and the shorter charging window has tangible value. Buying a 22 kW-labelled wallbox does not upgrade the vehicle’s onboard charger or the grid connection.
The nominal ratings come from electrical fundamentals: 230 V × 32 A ≈ 7.36 kW on one phase; √3 × 400 V × 16 A ≈ 11.1 kW across balanced three-phase supply; and √3 × 400 V × 32 A ≈ 22.2 kW. They represent maximum AC input under appropriate conditions, not guaranteed power entering the traction battery. Supply limits, the car’s onboard AC charger, charge settings, load balancing and losses all affect the outcome. Tesla’s UK onboard-charger guidance, for example, lists up to 7.4 kW single-phase and 11 kW three-phase for current Model 3, Y, S and X configurations; verify the exact model and variant before buying.
Buying recommendation: confirm the car’s AC charging limit, the number of phases at the property and the network operator’s approved capacity before asking for wallbox quotations. Compare installed totals and features—dynamic load management, CT meter, solar surplus mode, off-peak scheduling, Home Assistant access, protective devices and commissioning—rather than hardware kW alone. This guide uses UK electrical and network rules; buyers elsewhere must obtain advice under their own local regulations.
At a glance: 7 kW versus 11 kW versus 22 kW
| Charger label | Typical supply and current | Idealised AC output | Vehicle requirement to realise rating | Usually the best fit |
|---|---|---|---|---|
| 7 kW or 7.4 kW | 230 V single-phase, up to 32 A | 7.36 kW | Car accepts 32 A on one phase | Most UK houses and overnight charging |
| 11 kW | 400 V three-phase, up to 16 A per phase | 11.1 kW | Car has 11 kW three-phase AC onboard charger | Houses already on three-phase; some multi-car use |
| 22 kW | 400 V three-phase, up to 32 A per phase | 22.2 kW | Car supports 22 kW three-phase AC | Selected high-use vehicles and sites with ample spare capacity |
These figures assume the supply is healthy, the charger is configured for its rated current and neither the car nor the installation is imposing a lower limit. UK and continental terminology varies: 7 kW, 7.2 kW and 7.4 kW commonly describe the same general 32 A single-phase class; do not treat tiny nominal differences as a meaningful speed advantage. Likewise 11 kW and 22 kW are three-phase AC categories, not battery sizes.
The cable connection is AC Mode 3 charging, generally using a Type 2 connection in the UK and most of Europe. The wallbox supplies and controls AC power; the onboard charger inside the car converts that AC to DC. High-power public DC fast charging works differently because the external charger performs that conversion and bypasses the car’s AC onboard power limitation.
What really limits charging speed?
There are four independent ceilings. Available grid and installation capacity comes first: a charger cannot be configured to draw more than the supply and protective equipment safely allow. Wallbox hardware and commissioning settings come next: a 22 kW-capable device might be configured at 11 kW or less. The cable, plug and authorised current must also support the intended operation. Finally the vehicle’s AC onboard charger limits how much power reaches the battery even when the chargepoint can provide more.
The effective AC charging power is approximately the lowest applicable limit; the actual power can be lower still because the battery management system reduces charging as necessary. Battery heating or cooling, state of charge, cell temperature, supply voltage and vehicle software settings can all alter results.
A common misconception is that a 22 kW wallbox automatically delivers 22 kW to any EV. Imagine a car with an 11 kW three-phase onboard charger. Plug it into a correctly configured 22 kW wallbox and the vehicle will ordinarily still draw no more than around 11 kW AC. Installing the more powerful box does not increase the car’s acceptance rate. Equally, a car described as capable of 11 kW AC may have a lower limit when connected to a single-phase supply; check the exact vehicle specification for both connection types.
Illustrative vehicle and supply combinations
| Available wallbox and supply | Car AC acceptance | Approximate maximum AC draw | Why |
|---|---|---|---|
| 7.4 kW single-phase | 7.4 kW single-phase | 7.4 kW | Both match |
| 22 kW three-phase | 11 kW three-phase | 11 kW | Vehicle onboard charger is the cap |
| 11 kW three-phase | 22 kW three-phase | 11 kW | Wallbox/current limit is the cap |
| 22 kW three-phase | 7.4 kW single-phase only | Up to 7.4 kW if 32 A on that phase is permitted | Vehicle uses one phase, subject to phase and supply constraints |
| 7.4 kW single-phase | Vehicle accepts only 16 A on that phase | About 3.7 kW | Vehicle’s per-phase limit dominates |
| 22 kW-labelled hardware configured to 16 A per phase | 22 kW three-phase | About 11 kW | Installation setting caps all three phases |
The cases above are illustrations, not a compatibility certificate. Three-phase charging behaviour differs across cars, particularly when the car has multiple onboard-charger modules or regional charging options. Some vehicles can accept 22 kW AC; others offer 11 kW as the maximum even though public chargers prominently advertise 22 kW. Use the manufacturer’s exact model-year data, not generic brand or battery-capacity descriptions.
Single-phase and three-phase supplies explained
A typical UK residential property has a single-phase service at nominal 230 V. A 32 A EV charging circuit then draws a little over 7 kW while charging at full output. The entire EV demand lands on one live phase, so the electrician must assess simultaneous consumption by showers, cookers, heat pumps, immersion heaters and other large loads. A charger’s dynamic load balancing can reduce the EV current when household demand rises, but it does not create additional supply capacity.
A three-phase service offers three line conductors with approximately 400 V between phases and 230 V between each line and neutral. A 16 A three-phase charger spreads its approximately 11 kW across those phases. At 32 A per phase, the theoretical ceiling becomes about 22 kW. The three-phase distribution is helpful where a home already has suitable electrical infrastructure, but equipment compatibility, phase imbalance and supply headroom must still be checked.
Do not assume that owning a three-phase house makes 22 kW free or straightforward. There may be multiple EVs, an air-source heat pump, a workshop, PV inverters or other demanding circuits. The installer needs to evaluate the site’s per-phase loads and protective arrangement, not just sum the service fuse ratings. Building management or shared parking installations can also have feeder, metering and landlord permissions beyond the home’s consumer unit.
Can I use an 11 kW charger on a single-phase house?
An EV charger sold as an 11 kW three-phase model may or may not have a manufacturer-approved single-phase operating mode. If it does, it generally cannot deliver 11 kW from an ordinary 230 V 32 A single-phase circuit; 230 × 32 gives about 7.4 kW, and some three-phase-designed equipment has stricter single-phase limits or will not operate at all. Check the actual manufacturer wiring configuration and certification; never assume phase conversion is possible by connecting terminals differently.
Similarly a 22 kW wallbox may be a configurable 7.4/11/22 kW model, but that must be documented for the exact regional hardware variant. Its label is an upper rating, not permission to install it on a supply that cannot sustain it.
Charging time: worked 42 kWh example
Charging power is measured in kW; transferred energy is measured in kWh. The simplest estimate is energy required ÷ average power. To compare real household outcomes, account for AC-to-battery charging losses as well. Losses vary by car, power level and thermal conditions; the 90% efficiency assumption below is an illustrative calculation only, not a test result or universal constant.
Suppose the driver wants 42 kWh added to the battery between arriving home and leaving again. At an assumed 90% overall charging efficiency, the electricity taken from the wall is 42 ÷ 0.90 = 46.7 kWh. Under constant ideal AC input, the times become:
| Effective AC draw | AC required | Idealised time to add 42 kWh to battery | Practical interpretation |
|---|---|---|---|
| 3.7 kW | 46.7 kWh | 12.6 hours | May not fit a short overnight tariff |
| 7.36 kW | 46.7 kWh | 6.3 hours | Fits many overnight stays, not necessarily a four-hour cheap window |
| 11.04 kW | 46.7 kWh | 4.2 hours | Useful if car, three-phase supply and installation all support it |
| 22.08 kW | 46.7 kWh | 2.1 hours | Only if vehicle really accepts approximately 22 kW AC |
| 22.08 kW-rated wallbox with 11 kW car | 46.7 kWh | About 4.2 hours | Paying for 22 kW does not beat the onboard limit |
This is an energy-balance illustration, not a guaranteed charge time. A car may taper or interrupt charging for temperature management; the wallbox may be load-balanced down, and the efficiency figure can change. If a manufacturer quotes a particular 10–80% or 20–80% time, follow its conditions rather than applying this calculation as a certification.
What fits into a four-hour cheap-electricity window?
A tariff with four low-price hours is a good test of whether you need more power. Using the same 90% illustrative efficiency, four hours at 7.36 kW moves 29.4 kWh from the wall, or 26.5 kWh into the battery. At 11.04 kW the comparable figures are 44.2 kWh from the wall and 39.7 kWh into the battery. At a genuine 22.08 kW they are 88.3 kWh from the wall and 79.5 kWh into the battery—although the car’s battery and its allowable charging power may make the last case impossible.
If daily driving consumes 12 kWh from the battery, even a derated 7 kW chargepoint usually has abundant overnight time to replenish it. If a two-car household needs 40–60 kWh added overnight and only one vehicle can use the driveway charger at a time, 11 kW might bring practical value. The answer depends much more on daily energy and parking time than the absolute size of the EV battery.
Does 22 kW save money on an EV tariff?
A faster wallbox does not automatically make each kWh cheaper. If all charging happens on the same flat-rate tariff and efficiency is similar, charging 42 kWh into a battery uses approximately the same electricity whether it takes two or six hours. The economic benefit appears when higher power moves electricity into a shorter low-rate period, avoids expensive public top-ups or serves several vehicles in succession.
As an illustration, suppose you need 39 kWh in the battery, charging efficiency is 90%, and cheap and peak grid electricity cost 10p and 30p per kWh respectively. The wall needs roughly 43.3 kWh. If 7.36 kW is available for four cheap hours, it can purchase about 29.4 kWh in that window; the remaining 13.9 kWh is paid at peak rate if you must finish before departure. The electricity cost is £2.94 + £4.17 = £7.11. If 11.04 kW fits essentially all 43.3 kWh into the four-hour window, cost is around £4.33. The example therefore shows £2.78 saved on that particular charging event, not £3.00 saved every night or a general tariff promise.
| Worked comparison | 7.36 kW for four cheap hours | 11.04 kW for four cheap hours |
|---|---|---|
| Battery energy required | 39 kWh | 39 kWh |
| Wall energy at 90% assumed efficiency | 43.3 kWh | 43.3 kWh |
| Wall energy at cheap rate | 29.4 kWh | 44.4 kWh |
| Wall energy charged at peak rate | 13.9 kWh | 0 kWh |
| Example charging cost, 10p/30p | £7.11 | £4.33 |
If you have six or more cheap hours, the standard 7 kW wallbox may already meet the requirement. If the EV is at home for an entire night and charging can be scheduled flexibly, buying a three-phase connection solely to save a few hours may offer poor value. Smart tariffs may also use variable cheap slots or vehicle-managed schedules; confirm actual terms, supplier support for your car/charger, export rates, and the consequences of charging outside allocated windows.
Energy Saving Trust notes that time-of-use or EV tariffs can reduce costs when drivers can shift demand. That benefit comes from tariff selection and scheduling, not the nameplate charger rating by itself.
The installation question: can the house actually support it?
A professional survey should identify the network service arrangement, single- or three-phase supply, service fuse and agreed capacity, earthing system, existing electrical loads, route to parking, cable conditions, suitable protective devices and whether grid-network approval is needed before installation. The UK government guidance directs installers to the Energy Networks Association (ENA) application/notification process and says the installer should determine whether the distribution network operator (DNO) must be informed before or after work.
The ENA network process is not optional paperwork you can work around with Home Assistant. A smart current cap may allow a compliant installation on an existing service, but the design and any network notification/approval must reflect the limits. Converting an ordinary single-phase service to three-phase could require network works, a revised metering arrangement, board alterations, trenching, long lead times or costs that dwarf a wallbox upgrade. Get a written site-specific quotation before committing.
The installer must assess these constraints
| Item to verify | Why it matters | Ask for this evidence |
|---|---|---|
| Actual supply and phase count | 11/22 kW operation requires a usable three-phase source | Survey findings and supply characteristics |
| Per-phase capacity and house maximum demand | EV charging is a sustained load and can coincide with heating/cooking | Load assessment and proposed configured current |
| DNO notification/approval | Network connection requirements depend on situation | ENA submission/approval or installer explanation of process |
| EVSE certification and UK compliance | Equipment must suit UK supply, safety and smart-chargepoint rules | Exact UK model identification and compliance documentation |
| Protective measures | EV circuits require appropriate fault and shock protection | Designed RCD/DC fault/PEN protection and test results |
| Cable route and installation conditions | Length, enclosure, thermal conditions and voltage drop affect design | Itemised quotation showing cable route and groundworks |
| Load management | Prevents site overload while other loads operate | CT/meter details, controlled current range and fail-safe test |
| Warranty, firmware and connectivity | Charging must remain safe if internet or Home Assistant fails | Warranty terms and documented offline operation |
The IET and BSI published Amendment 4 (2026) to BS 7671:2018 in April 2026. A qualified installer should work to the applicable UK rules at installation time, including protective arrangements around open-PEN conditions where relevant, residual-current and DC leakage requirements, isolation and circuit protection. This article does not provide instructions for wiring mains terminals, bypassing protective devices or modifying the vehicle’s charging interlocks.
What about the service fuse and consumer unit?
Do not treat a marked 60 A, 80 A or 100 A service fuse as a blanket statement that another 32 A continuous load is available. The figure does not tell you the building’s real maximum demand, the DNO agreement, the circuit design or the demands of other equipment. Equally, a large-looking main board does not prove the incoming connection supports 22 kW. The installer must assess the complete electrical installation and network conditions.
Dynamic load management can reduce charging current when household demand rises. It is valuable for heat-pump homes and future-proofing, but the chosen charger must respond correctly to its own metering device if the internet or Home Assistant fails. Software automations may optimise the charging schedule; they must not be the only safety mechanism preventing overload.
Should you buy a 22 kW-capable wallbox for future-proofing?
Sometimes, but specify what is being future-proofed. A configurable 22 kW wallbox installed on a three-phase circuit with a temporary 16 A-per-phase setting can make sense if network and electrical permissions permit and the installer has designed for later expansion. It could avoid replacing the charger when a future 22 kW-capable car arrives. However, upgrading the wallbox label without upgrading the supply, protective devices, distribution board and cable does not deliver future capacity.
Consider the trade-off between extra hardware cost today and uncertain vehicle adoption. Many popular battery-electric cars charge at up to 11 kW AC even on a 22 kW supply. Tesla’s published UK onboard-charger table demonstrates this for a common set of cars. A future EV could support 22 kW, but today’s purchase should not assume it will. Homeowners should check whether the manufacturer allows safe configurable current and later recommissioning by an electrician.
For many households, spending on reliable connectivity, a tethered cable of appropriate length, supported load management and a credible installer is a better long-term investment than unused maximum output. Cable-management ergonomics matter every day; an extra 11 kW of rarely usable capacity might not.
Solar panels, batteries and Home Assistant: what changes at 11 or 22 kW?
EV charging is a large adjustable household load and an attractive target for solar surplus automation. However, domestic PV rarely supplies 11–22 kW of spare power continuously, especially once other appliances and the home battery are accounted for. Buying a higher-rated wallbox does not turn intermittent PV into continuous 22 kW generation. In many homes the most useful feature is not maximum current, but the ability to modulate current gradually while respecting the car’s and chargepoint’s minimums.
A typical AC EV follows a charging protocol with minimum usable current thresholds. For many three-phase Mode 3 situations, a 6 A-per-phase lower boundary corresponds to roughly 4.1 kW across three phases, whereas 6 A on one 230 V phase is roughly 1.4 kW. Some chargers can switch between single- and three-phase operation to absorb lower solar surplus, but not every wallbox offers approved automatic phase switching; verify specific vehicle and EVSE compatibility before choosing it.
Why current limits need phase awareness
An 11 kW three-phase wallbox is using about 16 A on each phase at full output. Reduce it to 10 A and it draws roughly 6.9 kW, not 2.3 kW, if all three phases remain active. A one-phase car that happens to draw 10 A uses only about 2.3 kW instead. This distinction matters for Home Assistant automations: a number entity named charging_current may mean amps per active phase, not total current across phases.
The correct way to evaluate a solar charger is to inspect the manufacturer’s PV meter/CT support, phase measurement, export-detection logic, minimum current behaviour and cloud dependence. For Home Assistant, useful entities include real charging power, cumulative kWh, actual active phases where available, maximum offered current, charge state and grid import/export. Do not calculate imported energy by adding the grid meter’s total to the EV meter; that double-counts the car as an appliance within the home’s metered consumption.
| Integration feature | Why it matters | What to verify |
|---|---|---|
| Local API, supported OCPP or native integration | Automation resilience and privacy | Exact charger/firmware support; whether cloud access is still required |
| Measured power (kW) and energy (kWh) | Honest Energy dashboard accounting | Whether data covers charger input, car energy, or session-only totals |
| Charger current limit | Dynamic load and tariff response | Whether changes are persistent and accepted by the car |
| Three-phase/single-phase switching | Better low-solar utilisation | Manufacturer approval, switching conditions and contactor interlocks |
| Grid CT and battery priority | Prevents unwanted grid import or battery discharge | Compatible meter, CT orientation, configuration and failure mode |
| Local scheduling fallback | Keeps charging predictable if Home Assistant is offline | Autonomous EVSE behaviour and override options |
Home Assistant’s official OpenEVSE integration provides local monitoring and current control on supported firmware. For compatible third-party wallboxes, the community OCPP integration is another option but is not a built-in Home Assistant integration; actual charger functions depend on firmware and available measurands. Avoid assuming an OCPP badge guarantees reliable persistent charge-current control.
Cost comparison: budget for a completed installation, not just the box
A 22 kW product listing can look only modestly more expensive than a 7 kW product, but installed cost is the relevant figure. The budget must include certified hardware, labour, any additional metering and CTs, dedicated cabling, protective devices, testing, DNO-related work where applicable, groundworks, network upgrades, a warranty, and possible ongoing subscriptions. UK home installation ranges depend heavily on access and the site; Energy Saving Trust gives an indicative £800–£1,200 for a typical home chargepoint installation, not a quote for every location or a promise that three-phase conversion is included.
| Cost component | 7 kW on suitable single-phase | 11 kW on existing suitable three-phase | 22 kW with possible supply upgrade |
|---|---|---|---|
| Certified wallbox | Required | Required; confirm three-phase model | Required; confirm true 32 A three-phase rating |
| Electrician, circuit and protective devices | Required | Required; three-phase circuit design | Required; potentially larger components and route |
| Meter/CT and dynamic load management | Often advisable | Strongly advisable if site loads vary | Essential to consider carefully for constrained supplies |
| Network operator process | Assessment/notification as applicable | Capacity review and process as applicable | Greater chance site changes need approval or reinforcement |
| Cable run, trenching and enclosure | Site-dependent | Site-dependent | Site-dependent, potentially costlier |
| Change from one-phase to three-phase supply | Usually not needed | Not needed if suitable supply exists | Could dominate the project budget |
| Software/cloud fees and warranty | Check exact vendor terms | Check exact vendor terms | Check exact vendor terms |
Do not invent a precise upgrade cost from online averages. The price for a new three-phase service can be highly site-specific and depends on what the DNO must change. Obtain a written connection offer if a network upgrade is contemplated. Conversely, a property with three-phase already present and spare approved capacity may face relatively little additional cost for 11 kW. Compare real installer quotations with the same deliverables and warranty terms.
A practical five-year decision rule
Consider the incremental cost of choosing 11 kW over an adequate 7 kW solution, not the full cost of owning an EV. If that increment is £600 and it saves £2.78 per qualifying charging session as in the earlier illustrative tariff example, roughly 216 such sessions are needed just to cover that increment before discounting, future electricity price differences, maintenance, subscription costs and installation uncertainties. At only 20 qualifying sessions a year, that exceeds a decade; at 100 sessions a year, it is a little over two years. Those session counts and costs are hypothetical, designed to demonstrate how to build a decision—not actual payback forecasts.
For a household that already has enough cheap hours, the monetary saving may be close to zero even if 11 kW halves some wait times. More expensive equipment might still be worthwhile for convenience, multi-vehicle turnover or a future business use case, but value those reasons explicitly rather than presenting them as guaranteed electricity savings.
Buyer’s checklist before requesting quotations
- Check the exact car: obtain manufacturer documentation confirming maximum AC power on single phase and on three phase; confirm optional onboard-charger packages and regional variants.
- Identify the property supply: single/three phase, metering arrangement, approved capacity and loads. Ask the electrician to verify this on site.
- Quantify your actual daily demand: kilometres driven, typical kWh needed, times parked at home and the usable cheap-tariff window.
- Compare 7, 11 and 22 kW using the same conditions: do not compare idealised maximum hardware output with actual household derated performance.
- Discuss ENA/DNO requirements: the installer should assess whether connection notification or prior approval and any supply upgrade is necessary.
- Insist on an itemised installed price: cabling, protections, CTs, external isolators where required, groundworks, certification, testing and commissioning.
- Verify smart functionality: local versus cloud control, offline operation, tariff compatibility, authorised current limiting, firmware support and update policy.
- Check three-phase behaviour: whether the selected EVSE and the car handle single-phase operation or manufacturer-approved phase switching, if needed for PV surplus.
- Request protective-device documentation: the electrician should explain the RCD/DC leakage and open-PEN provisions appropriate to the installation and current regulations.
- Agree acceptance tests: confirm charger maximum current, derating, load balancing with other appliances, loss-of-network recovery and meter accuracy.
- Ask about expansion: if future EVs or a second charger are likely, seek a system-level load-management plan rather than assuming two 22 kW wallboxes can run simultaneously.
- Retain documentation: electrical certificate, network paperwork, charger settings, app details, warranty and measured results.
Common problems after installation
| Symptom | Possible explanation | Appropriate next check |
|---|---|---|
| 22 kW wallbox reports only 11 kW | Vehicle’s AC onboard charger limited to 11 kW | Verify vehicle and wallbox specifications; no unsafe workaround |
| Three-phase wallbox draws about 7 kW | Current set below nominal; car limits or demand management | Review documented site settings and event log |
| Chargepoint rated 7.4 kW charges at 3.7 kW | Car accepts 16 A single phase, or current was reduced | Check vehicle AC configuration and allowed chargepoint current |
| Charging slows when oven or heat pump runs | Dynamic load management operating correctly | Confirm site-current measurements and installer settings |
| Wallbox works but solar mode repeatedly stops | Insufficient surplus or minimum current/phase mismatch | Examine PV, grid import/export and controller hysteresis |
| Home Assistant says 22 kW but smart meter suggests lower draw | Wrong unit, phase multiplier, stale sensor or dashboard double counting | Compare real grid and charger power measurements |
| Charger loses smart schedule when Wi-Fi fails | Vendor cloud dependency or incorrect fallback | Verify approved offline schedule/firmware behaviour |
| Protective device trips | Possible fault, leakage, installation or supply issue | Stop charging and have a qualified electrician investigate |
Do not increase breaker ratings, bridge terminals, defeat fault detection or alter electrical protection in response to a slow charge rate. Software limits are not substitutes for certified protective design. The safe resolution to a charging constraint is to understand whether the vehicle, wallbox, installation or network is correctly imposing it.
Recommendations for typical UK households
Ordinary single-phase driveway, one EV, overnight parking
Choose a well-supported 7–7.4 kW smart chargepoint, professionally designed and installed with suitable site load management. Make reliability, tariff scheduling, customer support and a practical cable your buying criteria. If the car is parked from evening until morning, this often restores a typical day’s driving energy comfortably.
Existing three-phase service and an 11 kW-capable EV
An 11 kW three-phase wallbox is a credible upgrade when you need faster charging or need to complete charging within a shorter off-peak window. The installer should check per-phase headroom and whether the vehicle’s actual three-phase capability makes the upgrade worthwhile. If an approved configurable 22 kW model costs only slightly more, compare its warranty and features but have it commissioned at the permitted current.
Three-phase property with high turnover or a verified 22 kW AC car
Consider 22 kW if there is documented site capacity, the car can use it and faster turnaround clearly solves a real scheduling problem. Get written confirmation of total supply and installation costs, and request real commissioning measurements. A high-capacity charger is most defensible when it materially increases usable charging before the vehicle must depart.
Solar PV, battery and Home Assistant energy management
Prioritise measured import/export, reliable current modulation, approved metering, dynamic site protection and local integration rather than the kW badge. A 7 kW unit able to follow solar surplus and maintain cheap-tariff rules can outperform a cloud-dependent 22 kW unit for energy management. Do not let Home Assistant become a single point of failure for electrical safety.
Frequently asked questions
Is a 22 kW home charger three times faster than a 7 kW one?
Only under matching conditions. At nominal power, 22 kW is roughly three times 7.4 kW. The vehicle must accept 22 kW AC and the site must actually sustain it. An 11 kW-limited EV on a 22 kW point will not get a threefold speed boost. Battery charging losses and temperature conditions also affect real results.
Can I plug an 11 kW car into a 22 kW wallbox safely?
Generally yes with compatible, correctly installed Type 2 AC equipment: the car and chargepoint negotiate allowed current. The car draws within its onboard limit. The exact charger, vehicle and configuration still require normal manufacturer compatibility and approved installation.
Do I need a three-phase supply for 11 kW?
For the usual European/UK 11 kW AC charging arrangement, yes: around 16 A on each of three phases. A typical 230 V 32 A single-phase circuit supports roughly 7.4 kW instead. Special electrical installations and other regional supply arrangements should be assessed professionally rather than inferred from these common domestic examples.
Can a 22 kW charger be limited to 7 kW?
Some certified models support adjustable current and single-phase modes; others do not, or require installer tools. Confirm the exact manufacturer-approved configurations and never infer them from the power rating alone. A configured limit must align with the wiring and site approval.
Which rating is best for an EV with a 60 kWh battery?
Battery size alone cannot determine charger choice. More useful information is the daily energy deficit, hours available, the car’s AC acceptance, the electricity tariff and supply limitations. A car with a 60 kWh pack that uses only 10 kWh a day rarely requires 22 kW home charging.
Will 22 kW make my overnight EV electricity cheaper?
Only when it enables more charging within an eligible cheap-tariff window, or avoids a separate expense such as expensive public charging. If 7 kW already covers the required energy within the low-rate period, higher-rated hardware normally does not reduce the price per kWh by itself.
Does a 22 kW charger require DNO permission in the UK?
The installer must assess the network operator’s application/notification process and whether approval is required before connection. The specific route depends on the installation and service capacity. Do not assume an installation is exempt just because the wallbox can be software-limited.
Which wallbox is best for Home Assistant?
The answer depends on whether you need local monitoring, dynamic current commands, OCPP, vendor cloud scheduling, or a native integration. See the linked smart-charger buying guide and check the exact hardware and firmware. A wallbox’s power rating does not establish its API capabilities, and OCPP support alone is not proof of usable automation.
Official sources and verification links
- Tesla UK — Onboard Charger: example vehicle AC charging limits by phase and supply.
- UK government — Connecting EV chargepoints to the electricity network: network capacity and DNO assessment.
- UK government — Residential chargepoints minimum technical specification: nominal 230 V/400 V AC categories, equipment and standards.
- IET — Amendment 4 (2026) to BS 7671: updated UK wiring rules.
- Energy Networks Association — EV and heat pump connections: network application information.
- Energy Saving Trust — Charging electric vehicles: home charging and tariffs.
- Energy Saving Trust — Smart charging electric vehicles: typical installation-cost context and charging behaviour.
- Home Assistant — OpenEVSE integration: supported local charger controls.
- Home Assistant community OCPP integration — current-limit guidance: charger-current automation with compatible OCPP devices.
Related reading on esp32.co.uk
- ESP32 Modbus Energy Meter with Home Assistant — accurate measurements and energy accounting.
- ESP32 Energy Monitoring Methods Compared — CTs, pulse inputs and external meter limitations.
- Home Assistant Energy Dashboard Troubleshooting for ESPHome — correct units, counters and dashboard behaviour.
