Should your business install 7 kW or 22 kW AC chargers?

Choose AC chargers around parking time, vehicle capability and available power. A 22 kW unit needs a suitable three-phase supply, and a vehicle's onboard charger can limit the actual speed [S1]. Your business may get more useful charging from additional slower bays than faster labels. Compare complete installation costs and realistic use. Checked October 2026.

Last checked 16 October 2026

What is the difference between 7 kW and 22 kW AC chargers?

AC means alternating current. The car converts this electricity for its battery, so its onboard charging limit matters as well as the socket rating. Energy Saving Trust identifies both supply type and vehicle capability as checks before choosing business chargers [S1].

A kilowatt (kW) measures power; a kilowatt-hour (kWh) measures energy. Use power to size the electrical design and energy to model what drivers receive and pay for. A higher kW label does not establish more sessions or revenue. For the wider technology choice, read AC versus DC.

For socketed installations, include cable compatibility in the specification. The council guide identifies a three-phase 32 amp cable for full 22 kW delivery [S2].

How fast will a 22 kW charger charge your customers’ vehicles?

Use energy required ÷ actual charging power as a simplified time calculation [S1]. The following comparison assumes a 21 kWh top-up, constant power and no losses or interruptions. It is arithmetic, not a vehicle test.

Ask your installer to model the cars you expect and simultaneous use. Then compare the result with a normal visit. An overnight guest and a short-stay customer need different schedules. Do not take the fastest row as a commitment to every driver. Use dwell time and charger speed to prepare the operating brief.

Why might a commercial car park choose more slower chargers?

Compare completed top-ups across the car park. As an assumed design exercise, four sockets delivering 7 kW each need 28 kW at their outputs. Four delivering 22 kW each need 88 kW. Those sums exclude losses and other site loads; they are not a connection design. Ask the designer to test the actual simultaneous demand.

Energy Saving Trust describes load management that limits the combined charging demand to available capacity [S1]. Request a schedule showing what each car receives when every bay is occupied, rather than quoting only the unshared maximum. Include a response to interrupted communications in the proposed design.

Gather vehicle types, arrival times and departure deadlines. Ask the installer to demonstrate that the proposal serves those needs within the agreed capacity. Review signage and access before designating more bays: a driver who stays parked after charging can still prevent the next session. Compare that operational issue separately from electrical speed.

What could the chargers earn under each funding model?

The following is an illustration, not a quote for a paid destination installation. All inputs are assumptions, not observed utilisation or market prices. The example deliberately gives no automatic demand uplift to faster hardware. It excludes tax, finance, grants, rent, rates, payment fees and replacement reserves.

Annual energy E = daily sessions × 365 × 15. Sales = E × £0.50. Electricity = E × 1.10 × £0.25. Operating surplus N = sales − electricity − £600. In the mid case, E = 21,900 kWh and N = £10,950 − £6,022.50 − £600 = £4,327.50.

Fully funded income = sales × 5%. Part funded net = N × 50%; self funded net = N. Simple return on investment (ROI) = annual net ÷ host capital × 100. Payback = host capital ÷ annual net. Calculate from unrounded figures. With proportional contributions and shares, both investing models give the same illustrative ranges:

For a speed comparison, assume a 22 kW design adds £4,000 to capital but changes neither energy sold nor annual costs. At central capital of £16,000, mid-use self funded payback becomes £16,000 ÷ £4,327.50 = about 3.7 years, versus about 2.8 years at £12,000. Extra capital needs an evidenced operating benefit. Use your actual quotes in the ROI and payback guide.

What public charging and funding rules affect your choice?

For in-scope new paid public chargers, contactless requirements start at 8 kW per cable. Restricting output does not remove the requirement for a capable unit. Operator exemptions and access conditions need checking [S3]. Ask who handles payments and driver support, and request the recurring charges in the quote.

The Workplace Charging Scheme covers up to 75% of eligible purchase and installation cost, capped at £500 per socket and 40 sockets across an applicant’s sites, until 31 March 2027 [S4]. It is not an automatic discount for every public charging project. HMRC’s chargepoint first-year allowance extension runs to 31 March 2027 for Corporation Tax and 5 April 2027 for Income Tax [S5]. Check with your accountant; no relief is included above.

What should you do next?

Prepare vehicle and parking schedules, then request comparable power and cost proposals. Get matched with an installer that covers your area.

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