Key terms in electric vehicle charging

When you ask for a quote for a charging point, half a dozen terms come up that are not always explained. Here are the ones you genuinely need, with examples and without the waffle.

What a kW is

The kilowatt (kW) measures power, that is, the rate at which the charger delivers energy to the battery. The more kW, the faster it charges. It is the number on the unit's spec sheet: 7.4 kW single phase and 22 kW three phase is the norm for a domestic installation, and it is what all six models in the charger range.

What a kWh is

The kilowatt-hour (kWh) measures energy: what fits in the battery and what you use. It is what your supplier bills you for.

An example makes it quick to see. A 37 kWh battery, charging from 0 to 100% on a 7.4 kW home charger, takes around 5 hours. The same battery on a 60 kW fast charger takes a little over half an hour.

What consumption per 100 km is

It tells you how many kWh the car needs to travel 100 kilometres. The lower, the more efficient.

Following the example above: a car with a 37 kWh battery and a consumption of 18 kWh per 100 km has a range of around 200 km. With that figure and the price per kWh on your tariff you get the real cost per kilometre, which is the number worth comparing against petrol. You can do that calculation in our calculators.

AC charging

This is home charging and the medium-speed charging of public car parks. The grid supplies alternating current, and the car's onboard charger converts it to direct current to put into the battery.

That onboard converter is what sets the ceiling: it makes no difference that the charging point can deliver 22 kW if the car only accepts 7.4 kW on AC. AC charging typically runs between 2.3 kW and 22 kW, and it is the right one for charging overnight or during the working day.

DC charging

This is fast charging. The conversion happens in the station itself, which delivers direct current straight to the battery and bypasses the car's converter. That is why it can run from around 50 kW to over 350 kW and have the car ready in 20 or 30 minutes.

It is not a domestic option: it needs a power supply that a home does not have. It is what gets installed at charging stations and service areas.

Charging modes

You will see references to mode 3 and mode 4. Mode 3 is AC charging with a fixed charging point and communication between car and charger, which is what gets installed at home and in car parks. Mode 4 is the fast DC charging of public charging stations.

What OCPP is

The Open Charge Point Protocol lets a charger and a management system understand each other even when they come from different manufacturers. It is used for remote monitoring, for updating the unit and, above all, for billing its use.

For a domestic installation it is not usually needed. In a shared car park or at a business, where consumption has to be split, it is. From our range, the one that has it as standard is the V2C Trydan, on the V2C Trydan page.

What dynamic load balancing is

It is what means you do not have to increase your contracted power. The charger measures in real time how much the home is using and adjusts the power it sends to the car so that the total never exceeds what you contracted.

If the house is quiet, the car charges hard. If you put the oven, the hob and the washing machine on at once, the charger steps aside and catches up afterwards. Without this, the main power limiter would end up cutting the supply.

They do not all handle it the same way. The Woltio Pro includes the measuring sensor in the installed price, as you can see on the Woltio Pro page; on the Wallbox Pulsar Plus and the Tesla Wall Connector it is an optional accessory.

What solar surplus charging is

If you have solar panels, this is the function that sends the car the energy left over instead of exporting it to the grid. It needs a charger that supports it and a measuring device. We explain it in full in the article on solar power and electric car charging.

And in a shared car park

The terms are the same, but different ones matter: individual measurement of consumption, card activation and the ability to grow as more neighbours join. How that is approached is in installations in residents' associations.

Once these terms are clear, comparing quotes is far easier. Ours, with a fixed price by model, are in the charger range, and the grants currently available for installing a charging point ES apply to the total cost of the installation.