What is an electrical diversity factor?
Electrical diversity describes loads reaching their individual peaks at different times. A designer assesses their combined maximum demand, rather than assuming every rating coincides. For EV charging, the IET explains matching loads to supply without an assumed reduction, or using controls [S1]. An assumed 4 chargers at 7 kW total 28 kW before control. Checked October 2026.
What does electrical diversity mean for your site?
Electrical diversity is the effect of individual loads reaching maximum demand at different times. A diversity factor expresses the relationship between individual maxima and their combined peak; ask which convention a proposal uses before interpreting its number [S1].
For your site, this matters when sizing a supply for chargers alongside refrigeration, kitchens or machinery. ADMD means after diversity maximum demand [S2]. It is a demand assessment, rather than extra electrical capacity.
Can you assume chargers will not run together?
Do not assume a reduction simply because vehicles sometimes finish at different times. The IET’s charging guidance distinguishes assumed diversity from active control of charging demand [S1].
An illustration, not a quote: assume 4 chargers rated at 7 kilowatts (kW), a unit of power. Their combined rating is 4 × 7 = 28 kW. A designed charging limit of 14 kW would constrain their combined draw; it would not give every vehicle its full rated power simultaneously. All example figures are assumptions, excluding conversion losses.
What happens if load controls stop working?
Ask the designer to document the response to lost communications or monitoring, plus the protection against overload. The IET discusses these failure concerns and the need to follow equipment instructions [S1]. Ask for the limit and commissioning results in the handover documents.
Start with how many chargers your site needs and load management versus a grid upgrade. Use the charging cost tool for energy-cost arithmetic; it does not size electrical protection.
Next step
Take your proposed charging timetable to the site check, then get matched with an installer that covers your area.
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Common questions
What does ADMD stand for?
SSEN defines ADMD as after diversity maximum demand; it describes demand after allowing for diversity [S2].
Is there a universal percentage for commercial charger diversity?
No universal percentage is established by the IET webinar. It directs designers to assess loads and controls for the installation [S1].
Can the same allowance be used for a cable and a whole site?
The IET distinguishes individual circuit design from diversity across distribution boards and sites [S1].
Does diversity remove the need to balance phases?
No. The IET says designers must still consider phase balance and demand over time [S1].
Can a controller be sized using an assumed diversity reduction?
The IET says a charge controller is sized for its required operating parameters [S1].
Ask about your site
Sources
- Electrical Diversity and Load Curtailment webinar questions and answers, Institution of Engineering and Technology,Last checked 19 October 2026
- Glossary, ADMD, SSEN,Last checked 19 October 2026