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EV Charging Calculator (UK)

Free EV charging calculator for UK drivers. Estimate kWh drawn, charge time on a 7 kW home wallbox, electricity cost at 2026 Ofgem cap rates, and the savings if you charge from solar PV.

EV Charging Calculator

Energy drawn from the source
50 kWh
Time to reach target
6 h 45 min
Cost on grid only
£14
Cost after solar offset
£7
Saving from solar: £7
Granny / 3-pin (2.3 kW): emergency only.
7 kW home wallbox: full charge in 8-11 h.
Rapid (50 kW) and ultra-rapid (150-350 kW): 20→80% in 25-40 min.

How to use this calculator

Enter six values and the calculator returns the kWh drawn, charge time, and cost both with and without solar offset:

  1. Battery capacity (kWh) — your EV’s usable battery. UK 2026 mainstream: Tesla Model Y LR 75 kWh, Kia EV6 GT-Line 77, Hyundai Ioniq 5 84, Volkswagen ID.7 86, BMW i4 eDrive40 81, Polestar 2 LR 82.
  2. Charger power (kW) — most UK home wallboxes are 7.4 kW (32 A, single-phase). Tethered units from Ohme, Hypervolt, Andersen, MyEnergi, and Pod Point all fall in this band. 22 kW three-phase units exist but require a DNO upgrade for the typical UK home supply.
  3. Starting and target state of charge (%) — most manufacturers (Tesla, Kia, Hyundai, BMW) recommend 20-80% as the daily window for battery longevity. Long-trip days only — push to 100%.
  4. Electricity tariff per kWh — your unit rate in £/kWh. April 2026 Ofgem cap default: ~27p. Octopus Intelligent Go off-peak: 7p (23:30-05:30). British Gas Electric Driver off-peak: 9.9p. EDF GoElectric 35: 4.5p (00:00-05:00).
  5. Share covered by solar PV (%) — the proportion of charging energy supplied by your panels. 50% is realistic for a working household with EV plugged in evenings/weekends. 80%+ is achievable with a battery storage unit (Tesla Powerwall, GivEnergy, MyEnergi Libbi).
  6. Charging efficiency (%) — wall-to-battery. Default 90%. Real-world MyEnergi Zappi data shows 88-92% in mild UK temperatures, dropping to 82-85% below 5°C.

How the math works

The calculation is direct energy balance:

energy_to_battery (kWh) = battery_kwh × (target% - start%) / 100
energy_drawn (kWh)      = energy_to_battery / efficiency
charge_time (hours)     = energy_drawn / charger_kw
grid_cost (£)           = energy_drawn × unit_rate
solar_savings (£)       = grid_cost × (solar_pct / 100)
final_cost (£)          = grid_cost - solar_savings

Worked example for the en-gb defaults (75 kWh, 20→80%, 7.4 kW wallbox, 27p/kWh, 50% solar, 90% efficiency):

  • Energy to battery = 75 × 0.6 = 45 kWh
  • Energy drawn = 45 / 0.90 = 50 kWh
  • Charge time = 50 / 7.4 = 6.76 h ≈ 6 h 45 min
  • Grid cost = 50 × £0.27 = £13.50
  • Solar saving = £13.50 × 0.50 = £6.75
  • Final cost = £6.75 per session

A UK driver doing 8,000 miles/year on a 4 mi/kWh EV draws roughly 2,000 kWh of charging energy. At cap-rate 27p that’s £540/yr; on Intelligent Go at 7p that’s £140/yr; with 50% solar offset on cap rate that’s £270/yr. Compared to a 45 mpg petrol car at £1.45/litre (£11/100mi, £900/yr fuel), even cap-rate EV charging saves £360/yr.

UK charger types — wallbox, granny lead, and rapid

Granny lead (2.3 kW, 13 A 3-pin): Manufacturer cable for emergencies and PHEVs. Adds ~10 miles/hour. Continuous use of a 13 A socket above 10 A risks thermal damage to UK BS 1363 sockets — never daily-charge from a 3-pin.

Tethered home wallbox (7.4 kW): UK standard. Single-phase 32 A on a dedicated radial circuit. Smart functionality is mandatory under the EV Smart Charge Point Regulations 2021. Common brands and 2026 hardware-only prices: Ohme Home Pro £799, MyEnergi Zappi V2.1 £950, Hypervolt Home 3 Pro £799, Andersen A2 from £1,199, Pod Point Solo 3 £999.

Rapid (50 kW DC) and ultra-rapid (150-350 kW DC): Public-only. Gridserve, Osprey, BP Pulse, Ionity, Tesla Supercharger V4, InstaVolt. Typical 2026 rates: 70-89p/kWh ad-hoc, 50-65p subscribed. A 20→80% charge on 75 kWh costs £25-35 vs. £3.50 at home off-peak.

Charging from solar PV

The Smart Export Guarantee replaced Feed-in Tariff in 2020 — installers must now quote SEG-compatible inverters and DNO-G98 commissioning. Self-consumption is the priority: every kWh you self-consume is worth your import unit rate (27p), every kWh exported is worth 4-15p depending on supplier (Octopus Outgoing 15p, E.ON Next Export 16.5p, British Gas Export 6.4p).

A 4 kWp UK PV array (typical Energy Saving Trust mid-roof estimate) generates ~3,800 kWh/yr in central England (MCS Standard PV calc), more in the south. Pairing with a Zappi or Hypervolt that supports solar-only mode (Eco+ on Zappi, Solar mode on Hypervolt) lets you ramp the wallbox up and down to match real-time solar export — putting all surplus into the EV instead of exporting at 4-15p.

What changes the math

Lowers the cost (good)

  • Off-peak EV tariff (Intelligent Go, Octopus Go, EDF GoElectric, OVO Charge Anytime) — saves 60-75% vs. cap rate
  • Solar PV with diverter mode on the wallbox — captures surplus that would otherwise export at SEG rate
  • Battery storage to time-shift cheap-rate import to peak periods (effectively arbitrage at 20p/kWh delta)
  • 0% VAT on solar PV under the UK government’s energy-saving materials zero-rate, in force until March 2027

Raises the cost (bad)

  • Public DC rapid charging as a daily habit — 60-90p/kWh vs. 7p home off-peak
  • Standing charges counted in raw cost-per-kWh — Ofgem cap standing charge ~62p/day applies whether you charge an EV or not
  • Three-phase upgrade for domestic 22 kW — DNO connection charges of £2,500-6,000 are rarely justified on charging-time grounds alone

Pair this with the solar output calculator, savings calculator, and solar system cost calculator

The output calculator gives MCS-aligned annual kWh production for a UK array, savings translates that into £ saved on import, and cost gives the installed price for a typical 4-6 kWp domestic system.

Sources

Frequently asked questions

How long does a 7 kW wallbox take to charge an EV from 20% to 80% in the UK?
On a typical 7.4 kW (32 A single-phase) home wallbox — the UK standard — going from 20% to 80% on a 75 kWh battery (Tesla Model Y, Kia EV6, Volkswagen ID.4) takes roughly 6 hours 45 minutes once the typical 10% AC charging losses are included. The wall actually draws about 50 kWh to put 45 kWh into the battery. A 22 kW three-phase wallbox would do the same job in about 2 hours 15 minutes, but only households with a three-phase service (rare in domestic UK supply) can use the full 22 kW.
How much does it cost to charge an EV at home in the UK?
At the April 2026 Ofgem default tariff cap of about 27p/kWh for unit rate, a 20-80% charge on a 75 kWh battery costs around £13.50 of electricity. Switching to an EV-specific tariff like Octopus Intelligent Go (7p/kWh between 23:30-05:30) drops the same charge to about £3.50 — a typical UK driver doing 8,000 miles/year saves £450-600 a year by switching to an EV tariff alone, before considering solar.
Are home solar panels worth it for charging an EV in the UK?
Yes for daytime/weekend charging and surplus export. A typical UK 4 kWp domestic array generates about 3,800 kWh annually (MCS PV calculator, central England), enough to cover roughly 12,000 EV miles a year on a 4 mi/kWh car. Smart Export Guarantee (SEG) tariffs from Octopus Outgoing, E.ON Next, and EDF pay 4-15p/kWh for exported surplus — pairing solar with an EV that's plugged in during midday raises self-consumption from 30% (no EV) to 50-65% (EV at home midday).
Do I need a 7 kW or 22 kW home wallbox?
Almost every UK home has single-phase 60-100 A supply, which limits domestic EV charging to 7.4 kW (32 A). A 22 kW (three-phase) wallbox requires a three-phase service upgrade — typical cost £2,500-6,000 including DNO connection charges. For 95% of UK drivers, a 7 kW unit fully refills a typical EV overnight (8-11 hours from empty) and the cost saving on a three-phase install is rarely recovered. Brands: Ohme, MyEnergi Zappi, Andersen, Hypervolt, Pod Point.
What is the UK regulatory framework for home EV chargers?
The Electric Vehicles (Smart Charge Points) Regulations 2021 require all new home and workplace chargers sold in Great Britain to support smart functionality (default off-peak charging, randomised delay, demand-side response capable). BS 7671 18th Edition Section 722 covers EV charging installations; a Type A or Type B RCD is required and PME (Protective Multiple Earthing) requires either an earth electrode or a PEN-fault detection device — an OCPP/IEC 61851-compliant smart charger handles this in software.

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