In short: this glossary explains the terms that come up most when planning EV charging and battery storage, from kW and kWh to OCPP, flexible connections and state of health. Each entry is a plain-English definition, with a link to a fuller article where we have one.
Charging projects bring together vehicles, electrical engineering, energy markets and software, and each brings its own vocabulary. We have grouped the terms by topic so related ideas sit together.
Power and energy
kW (kilowatt): a measure of power, the rate at which energy flows. A charger’s kW rating tells you how fast it can deliver energy, if the vehicle can accept it.
kWh (kilowatt-hour): a measure of energy. A battery’s size is given in kWh. A 7 kW charger running for one hour delivers 7 kWh.
kVA (kilovolt-ampere): a measure of apparent power, often used for grid connections and generators. It is close to kW when the load’s power factor is near 1.
Power factor: the ratio of real power (kW) to apparent power (kVA). Good chargers have a power factor close to 1, so they make efficient use of the connection.
Peak demand: the highest power a site draws, often measured over half-hour periods. It drives connection size and, on many tariffs, part of the bill.
Load profile: how a site’s power use changes through the day. It is the starting point for sizing chargers, storage and connections.
Charging types and connectors
AC charging: the vehicle’s own on-board charger converts AC from the grid to DC for the battery. It is usually slower and suits long stays such as overnight at a depot.
DC charging: the charger converts AC to DC itself and feeds the battery directly, allowing much higher power.
Rapid charge point: in Great Britain’s public charging rules, a charge point of 50 kW or more.
Ultra-fast or high-power charging: DC charging at roughly 150 kW and above. Hyundai, for example, defines ultra-fast charging as 150 kW to 350 kW. See 150 kW vs 350 kW chargers.
Type 2: the standard AC connector for cars and vans in the UK and Europe.
CCS (Combined Charging System): a connector that adds two DC pins to an AC connector. CCS2, based on Type 2, is the common DC connector in the UK and Europe. CCS1 is the North American version.
CHAdeMO: an older DC connector standard, now uncommon on new vehicles in Europe.
NACS / SAE J3400: the North American Charging Standard connector, developed by Tesla and standardised through SAE as J3400.
MCS (Megawatt Charging System): a charging standard for heavy vehicles. CharIN lists its limits as up to 1,250 volts and 3,000 amps DC. More in electric HGV charging.
Dwell time: how long a vehicle stays parked where it can charge. It decides how much power you really need.
Charging curve: the way a vehicle’s charging power changes as its battery fills. Power is usually highest at low states of charge and falls as the battery approaches full.
Dispenser: the unit in each bay of a distributed charging system, holding the cable and screen but little of the power electronics.
Distributed charging system: one central power cabinet feeding several dispensers and sharing power between them. Compared in distributed vs standalone chargers.
Grid and connections
DNO (distribution network operator): the company that owns and runs the local electricity network in your area and provides connections to it.
IDNO (independent distribution network operator): a licensed company that builds and runs smaller networks, such as on new developments, connected to the DNO’s network.
ICP (independent connection provider): an accredited contractor that can build some connection works instead of the DNO.
Budget estimate: an indicative cost for a connection, without detailed network studies. It cannot be accepted.
Connection offer: a formal quotation based on network studies, with a cost and terms you can accept.
Reinforcement: upgrades to the wider network, such as a new transformer or cable, needed to supply a new connection.
Flexible connection: a connection where your import can be limited at certain times, in exchange for an earlier or cheaper connection. Also called non-firm, curtailable or timed connections.
DUoS (Distribution Use of System) charges: network charges on business electricity bills, often higher in a red time band in the early evening.
Load management: software or hardware that shares available power between chargers so a site stays within its limit. See load management for depots.
Smart charging: charging that is scheduled or adjusted in response to prices, site load or grid signals.
Batteries and storage
BESS (battery energy storage system): a battery with its power conversion, controls and safety systems, installed to store and release electricity.
Battery-buffered (or battery-boosted) charging: chargers paired with on-site storage so a small connection can deliver high charging power. See why battery-boosted charging matters.
Usable capacity: the energy a battery can actually deliver, usually less than its nominal capacity.
State of charge (SoC): how full a battery is, as a percentage.
State of health (SoH): a battery’s remaining capacity compared with when it was new.
Depth of discharge (DoD): how much of the battery’s capacity is used in a cycle.
Cycle: one full charge and discharge, or the equivalent in partial cycles.
C-rate: charge or discharge power relative to capacity. A 100 kWh battery delivering 100 kW is at 1C.
Round-trip efficiency: the share of energy put into a battery that you get back out.
LFP (lithium iron phosphate): a lithium-ion chemistry widely used for stationary storage and many vans.
Mobile energy storage: a battery system that can be moved to where power is needed. See mobile energy storage explained.
Software and protocols
CPMS (charge point management system) or back office: the software that monitors chargers, controls access and pricing, and reports usage.
OCPP (Open Charge Point Protocol): the open protocol chargers use to talk to a back office, so hardware and software can come from different suppliers. Explained in OCPP explained for charger buyers.
OCPI (Open Charge Point Interface): a protocol that connects charge point operators with mobility service providers, so drivers can use one app or card across networks.
ISO 15118: a standard for communication between vehicle and charger. It enables Plug & Charge, where the car identifies itself and billing starts automatically.
V2G (vehicle-to-grid): using a vehicle’s battery to send power back to the grid or a building. V2X covers all such uses.
Rules, roles and contracts
CPO (charge point operator): the company that runs charge points and is responsible for their operation.
eMSP (e-mobility service provider): a company that gives drivers access to charging through an app or card.
Uptime: the share of time a charger is working and available. Public rapid networks in Great Britain must meet 99% reliability. See charger uptime and service levels.
SLA (service level agreement): the contract terms that set response times, repair times and uptime targets, with remedies if they are missed.
OEM (original equipment manufacturer): a factory that builds a product to your design.
ODM (original design manufacturer): a factory that designs and builds a product you sell under your own brand. See working with an ODM.
UKCA and CE marking: conformity marks showing a product meets the relevant product safety rules for Great Britain and the EU respectively.
BS 7671: the UK wiring regulations, which include specific requirements for EV charging installations.
Frequently asked questions
What is the difference between kW and kWh?
kW is power, the rate of charging. kWh is energy, the amount delivered or stored. A van needing 60 kWh overnight would need around nine hours on a 7 kW charger, a little longer once charging losses are included.
What does “50 kW charger” mean for my vehicle?
It is the most the charger can deliver. The vehicle may accept less, and power usually falls as the battery fills.
Is a flexible connection the same as load management?
No. A flexible connection is an agreement with the network operator about when you can import power. Load management is how your site shares whatever power it has between chargers.
If a term on your project is not here, or you want help turning the jargon into a decision, our solution recommendations service can help. Send us your question.
