How to Plan Charging Locker Capacity

Charging locker capacity should be calculated from the number of devices that genuinely need secure charging at the same time, then converted into the number of complete charging-locker units required. Total device population is only the starting point.

This guide shows how to calculate how many charging locker compartments and complete locker units you need. It covers total device numbers, peak simultaneous charging demand, spare or growth allowance, unit conversion, rounding up partial locker requirements and future expansion.

For the wider charging-locker specification process, start with the Charging Lockers UK guide.

Quick answer: how many charging locker compartments do I need?

Use two calculations.

Required charging positions = peak simultaneous charging demand + chosen spare/growth allowance

Then convert the result into complete locker units:

Number of locker units = required charging positions ÷ usable charging positions per locker, rounded up

Always round the locker-unit result up to the next complete unit. A calculation of 2.1, 2.5 or 2.9 lockers still requires 3 complete lockers.

There is no universal spare-capacity percentage that suits every site. Choose an allowance that reflects the likelihood of growth, temporary devices, replacement equipment and changes in use.

What charging locker capacity actually means

Charging capacity is the number of usable charging positions required to support the real operating pattern of a school, workplace or facility.

That is different from simply counting the total number of devices owned by the organisation. Some devices may be in use while others are charging. Some may never need to return to the locker at the same time. Others, such as a class set or shift-issued equipment, may all return together.

Capacity figure	What it means
Total device population	Every device the charging system may need to support
Peak simultaneous charging demand	The maximum number likely to need a charging position at the same time
Spare/growth allowance	Additional positions deliberately provided for expansion, replacements or operational resilience
Required charging positions	Peak simultaneous demand plus the chosen allowance
Usable positions per locker	The number of charging positions in the specific locker configuration being considered
Required locker units	Required charging positions divided by usable positions per locker, rounded up

Step 1: count the total device population

Start by identifying every device group that may need to use the charging system.

• laptops;
• Chromebooks;
• tablets;
• phones;
• radios;
• barcode scanners;
• handheld terminals;
• tool batteries;
• loan or replacement devices;
• future devices already planned for purchase.

Keep different device pools separate at this stage if they have different return patterns. Twenty laptops that return overnight and twenty scanners that return at shift handover should not automatically be treated as one forty-device demand figure.

Step 2: identify peak simultaneous charging demand

The most important capacity figure is the maximum number of devices that realistically need charging at the same time.

Use the busiest normal charging period rather than the daily average.

• School class set: if all tablets return after the final lesson, peak demand may equal the complete set.
• Hybrid office: if only part of the laptop fleet is ever returned together, peak demand may be much lower than total ownership.
• Warehouse: if radios or scanners return together at shift handover, the handover period may define peak demand.
• Mixed workplace: different device groups may reach their peaks at different times and may need separate calculations.

Do not reduce the figure because devices are usually staggered if there are predictable periods when more equipment returns together. Capacity should survive the busiest routine condition the site expects to handle.

The operational differences behind these patterns are covered in Charging Lockers for Schools vs Workplaces.

Step 3: choose a spare or growth allowance

Once peak simultaneous demand is known, decide whether additional charging positions should be provided.

There is no universal percentage that should automatically be added. The appropriate allowance depends on the site.

• Are more laptops or tablets already planned?
• Is pupil, employee or membership growth likely?
• Are temporary or loan devices regularly added?
• Could new shifts or teams increase peak demand?
• Would spare positions help when a device is replaced or moved between groups?
• Is it difficult or expensive to add another locker later?
• Is the device population stable enough to plan tightly?

The organisation should choose and document its own allowance. For one stable fleet it might be only a small number of additional positions. Another site may deliberately reserve more expansion capacity because growth is already expected.

Step 4: calculate the required charging positions

Once peak demand and the chosen allowance are known, calculate the number of charging positions required.

Required charging positions = peak simultaneous charging demand + chosen spare/growth allowance

For example:

Peak simultaneous demand	Chosen allowance	Required positions
18	2	20
32	4	36
16	4	20

This calculation tells you how many usable charging spaces the installation needs. It does not yet tell you how many complete locker cabinets to buy.

Step 5: convert charging positions into complete locker units

Next, take the required charging positions and divide them by the number of usable charging positions in the specific locker unit being considered.

Number of locker units = required charging positions ÷ usable charging positions per locker

If the answer is not a whole number, round up.

Required positions	Positions per locker	Calculation	Complete lockers required
36	12	36 ÷ 12 = 3	3
20	10	20 ÷ 10 = 2	2
20	8	20 ÷ 8 = 2.5	3
25	12	25 ÷ 12 = 2.08	3

You cannot normally buy half a charging locker, and the unused positions in the final cabinet become part of the available capacity. Recheck the completed configuration so that the final result still matches your intended allowance and expansion plan.

Worked example 1: school tablet charging capacity

A school has a set of 32 tablets. All 32 are normally returned together at the end of the teaching day.

• Total device population: 32
• Peak simultaneous charging demand: 32
• School chooses additional capacity: 4 positions

Required charging positions = 32 + 4 = 36

The proposed charging locker has 12 usable charging positions.

36 ÷ 12 = 3 charging lockers

The school therefore needs 3 complete 12-position charging lockers.

Worked example 2: hybrid-office laptop capacity

A business owns 40 laptops, but attendance records and device-return patterns show that no more than 18 laptops normally require secure charging at the same time.

• Total laptop population: 40
• Peak simultaneous charging demand: 18
• Business chooses additional capacity: 2 positions

Required charging positions = 18 + 2 = 20

The chosen unit provides 10 usable charging positions.

20 ÷ 10 = 2 charging lockers

The business therefore needs 2 complete 10-position charging lockers. It does not need forty charging positions simply because forty laptops exist.

Worked example 3: warehouse shift equipment

A warehouse has 22 scanners and radios in operation. The largest normal return at a shift handover is 16 devices.

• Total device population: 22
• Peak simultaneous charging demand: 16
• Site chooses additional capacity: 4 positions

Required charging positions = 16 + 4 = 20

The proposed locker provides 8 usable positions.

20 ÷ 8 = 2.5

Round up to the next complete unit:

3 charging lockers are required.

Three 8-position lockers provide 24 positions, leaving four positions above the calculated 20-position requirement.

Worked example 4: mixed device pools

Mixed devices should not automatically be added together and placed into one locker type. First separate the equipment by charging pattern and by the kind of compartment each device requires.

For example, a facilities team has:

• 12 laptops, with a peak simultaneous return of 8;
• 18 handheld radios, with a peak simultaneous return of 14.

The organisation chooses 2 additional laptop positions and 2 additional radio positions.

Laptops: 8 + 2 = 10 required charging positions

Radios: 14 + 2 = 16 required charging positions

If a 10-position laptop locker and an 8-position radio-compatible locker are selected:

• Laptops: 10 ÷ 10 = 1 locker
• Radios: 16 ÷ 8 = 2 lockers

The mixed requirement therefore becomes 3 complete locker units across two suitable configurations.

Whether equipment physically fits the selected compartments is a different question. Check that separately using Charging Locker Sizes Explained.

How shared vs assigned use affects the calculation

The capacity calculation needs an agreed operating model. A permanently assigned charging position can remain reserved even when its normal user is absent, while a genuinely shared charging position may serve several users or devices at different times.

Do not try to solve that allocation question inside the capacity calculation. Decide the operating model first, then calculate peak simultaneous demand from it.

Use Shared vs Assigned Charging Lockers for pooled, individually allocated, role-based and hybrid charging systems.

One large charging locker or several smaller units?

Once the number of charging positions is known, the same capacity can sometimes be delivered by one larger charging bank or several smaller units.

Several smaller units may help when	One larger unit may help when
devices belong to different departments or areas	all equipment is issued and returned from one central point
different device types need different compartment formats	the device fleet is highly standardised
capacity needs to be distributed around a building	a single managed charging location is preferred
future expansion may be phased	the full requirement is known and needed immediately
one unit should remain available if another is being serviced	centralised supervision or administration is important

The physical location decision belongs in Where to Install Charging Lockers.

Always round partial locker requirements up

Locker-unit calculations commonly produce fractions. These must be rounded up because the required charging positions still have to exist physically.

Calculation result	Locker units to specify
1.1	2
1.8	2
2.01	3
2.5	3
3.0	3

Do not round 2.5 lockers down to 2 because that would leave part of the calculated charging demand unsupported.

Plan future charging capacity before the first installation

Future expansion can be handled in two ways:

• Build extra positions into the initial requirement through the chosen spare/growth allowance.
• Plan for an additional locker later by reserving suitable physical and electrical provision for expansion.

The correct approach depends on how certain the growth is. If additional devices have already been approved, including them in the calculation may be more sensible than treating them as vague future growth. If demand is uncertain, leaving a planned expansion route can avoid overbuying immediately.

Electrical supply for current and future charging units should be reviewed separately using Charging Locker Power Requirements Explained.

Common charging locker capacity mistakes

• Using total device ownership as the charging requirement. Peak simultaneous demand may be lower or may equal the whole fleet depending on the workflow.
• Using average demand instead of peak demand. Capacity needs to survive the busiest normal return period.
• Adding an arbitrary spare percentage. Choose an allowance that reflects the actual site’s growth and resilience needs.
• Stopping at the number of required positions. Convert positions into complete locker units before ordering.
• Rounding down a partial locker. Always round the unit requirement up.
• Combining incompatible device pools. Different devices may need separate locker configurations even when they share one capacity project.
• Ignoring the allocation model. Shared and assigned systems can create different peak-demand patterns.
• Ignoring expansion. A system that is full on day one may be expensive to extend later.
• Using compartment count without confirming usability. Physical device and charger fit must be checked on the dedicated sizing stage.

Charging locker capacity planning worksheet

Planning item	Your figure
Total device population	_____
Peak simultaneous charging demand	_____
Chosen spare/growth allowance	_____
Required charging positions	Peak demand + allowance = _____
Usable charging positions per proposed locker	_____
Raw locker-unit calculation	Required positions ÷ positions per locker = _____
Complete locker units required	Round up = _____
Total charging positions provided by final configuration	_____
Unused positions after installation	_____
Planned future expansion	_____

If the project contains several device groups, complete the calculation separately for each group before deciding whether they can use the same locker configuration.

What to decide after capacity

Next question	Use this guide
Will the devices and chargers physically fit?	Charging Locker Sizes Explained
Should charging spaces be pooled or individually allocated?	Shared vs Assigned Charging Lockers
What electrical supply or charging load is required?	Charging Locker Power Requirements Explained
Where should the lockers be positioned?	Where to Install Charging Lockers
How do school and workplace operating patterns differ?	Charging Lockers for Schools vs Workplaces
What is the complete specification process?	Charging Lockers UK Guide

Charging locker capacity FAQs

Charging locker capacity: summary

Charging locker capacity should be based on peak simultaneous charging demand, not automatically on total device population or total staff numbers.

First calculate the required positions:

Required charging positions = peak simultaneous charging demand + chosen spare/growth allowance

Then calculate complete locker units:

Number of locker units = required charging positions ÷ usable charging positions per locker, rounded up

Keep separate device pools separate where their return patterns or compartment requirements differ, and decide how future growth will be handled before installation.

When you are ready to compare products, view the Total Locker Service charging locker range. For the complete specification process, return to the Charging Lockers UK guide.