What is a self-storage unit mix?
A unit mix is the spread of unit sizes in a self-storage facility: how many lockers, small, medium and large units you have, and how many square metres each size takes up in total. That second figure is easy to lose sight of. Ten 1 m² lockers count as ten units, but together they take up less floor space than one 15 m² unit.
You can only divide your lettable floor area once, and every size has its own demand, price and price per m². A size that is full with a waiting list deserved more floor space; a size that stands empty for months ties up floor space that would have earned more elsewhere. So look past the occupancy of the whole facility, at what each size earns per m².
Revenue per available m², by size
Monthly rental revenue of that size ÷ total lettable m² of that size
Example: Fictional example: 20 units of 6 m² add up to 120 m². 18 are let at €117 a month, €2,106 in total. Revenue per available m²: €2,106 ÷ 120 = €17.55.
What storage unit sizes are there?
Every facility has its own unit sizes, but for analysis it helps to sort them into a few groups. The boundaries below are a working split, not a standard. Keep your own grouping fixed, so you can compare periods and facilities. Look at height as well as m²: two 5 m² units with different ceiling heights are not the same product to a tenant.
- Lockers and very small units, up to about 2 m²: boxes, archives and seasonal items. Relatively many walls, doors and locks per m².
- Small units, about 2 to 5 m²: the contents of a room or belongings during a renovation.
- Medium units, about 5 to 10 m²: part of a household during a move, or stock for a small business.
- Large units, from about 10 m² up to garage size: the contents of a whole home, business stock or equipment, sometimes with their own outside door.
How do you analyse your current unit mix?
Analyse size by size and over several months: occupancy by unit size in a single busy month tells you little.
Start with two exports: all units with size, status and street rate, and all running contracts with start date and actual rent. In TheStorageControl you filter units by size, price and status in a grid or table, and export the unit data for your own analysis.
Group both by size or size band and put these figures side by side for each group:
- Number of units and total m².
- Occupancy in units and in m².
- Monthly street rate and the price per m² that follows from it.
- Actual rent per m², after discounts and older rates.
- Revenue per available m², using the formula above.
- Waiting list and turned-away enquiries.
- Move-ins, move-outs and average length of stay.
- Tenants who moved to a larger or smaller unit.
Tip: record the demand you could not serve too
Your records show who rents a unit, not who walked away because their size was full. For every enquiry you could not meet, note the size requested, the date and whether the customer accepted another size. After a few months, that is your best measure of shortage by size.
Worked example: occupancy and price per m² by size
A fictional facility with 222 units and 1,460 m² of lettable floor space. The figures are made up to show the method, not as a benchmark for the market. Prices are street rates without discounts.
Counted in units, the facility is 87% occupied (194 of 222), but in m² only 81% (1,187 of 1,460 m²), because it is the large units that stand empty. The 3 and 6 m² sizes are full with a waiting list; the 15 and 20 m² sizes are not. The lockers have the highest price per m² and still have space, so more lockers would not solve anything here.
Revenue per available m² makes the gap concrete: at 3 m² it is 59 × €69 ÷ 180 m² = €22.62, at 15 m² it is 13 × €240 ÷ 300 m² = €10.40. A square metre in the large units earns less than half as much here.
| Size (fictional) | Units | Occupied | Occupancy | Price per month | Price per m² | Waiting list |
|---|---|---|---|---|---|---|
| 1 m² (locker) | 40 | 31 | 78% | €29 | €29.00 | No |
| 3 m² | 60 | 59 | 98% | €69 | €23.00 | Yes |
| 6 m² | 50 | 49 | 98% | €117 | €19.50 | Yes |
| 10 m² | 40 | 35 | 88% | €175 | €17.50 | No |
| 15 m² | 20 | 13 | 65% | €240 | €16.00 | No |
| 20 m² | 12 | 7 | 58% | €300 | €15.00 | No |
| Total | 222 | 194 | 87% (81% in m²) | – | – | – |
Signs your unit mix is off
You recognise a mix that does not match demand by signals that keep coming back month after month, not by one figure or one busy period:
- One or two sizes are consistently full with a waiting list, while other sizes stand empty for months.
- Occupancy in units is high, but occupancy in m² lags behind.
- Customers settle for a larger unit than they want, or walk away when their size is full.
- One size keeps needing a discount to get let.
- Tenants switch to a smaller unit as soon as one becomes available.
- Revenue per available m² differs widely between sizes, and the gap is not closing.
Adjusting: price by size, splitting or merging units
Start with the cheapest change you can reverse: the price per size. Raise the street rate of sizes with a waiting list; keep sizes with vacancies level or run a targeted promotion.
If the picture stays the same after a few pricing rounds, look at the layout. Splitting units means dividing a large unit that has been empty for a long time into sizes with a waiting list; merging is the reverse. Every new unit needs its own door onto a corridor, and a new wall costs floor space. Check fire safety, ventilation and any permits with your architect or local authority.
Other options are converting space, such as an unused office that can take lockers, and phasing: only fitting out part of the building once it is clear which sizes are in demand.
In TheStorageControl, splitting and merging units is part of standard unit management; the floor plan and availability follow automatically. For pricing, dynamic pricing gives advice per unit size and facility based on occupancy and demand, and you decide whether to apply it.
Whether a split pays off comes down to the payback period:
Payback period of a split
One-off cost of walls, doors and locks ÷ extra rental revenue per month
Example: Fictional, using the prices from the worked example: an empty 15 m² unit becomes two 6 m² units and one 3 m² unit. Once let, that brings in 2 × €117 + €69 = €303 a month. To earn the work back within 12 months, it may cost no more than 12 × €303 = €3,636. If the 15 m² unit was about to be let anyway, the extra revenue is only €63 a month (€303 − €240).
Planning the unit mix for a new facility
A new facility has no figures of its own yet. You build the first mix from research into local demand and design the building so you can adjust it later. There is no standard split that works everywhere. For developers and investors, the unit mix is an assumption in the business case that needs backing up.
Keep the number of sizes manageable: sizes that barely differ make the choice harder for customers. Research demand along these lines:
- Catchment: who lives and works within a reasonable travel time? Households that are moving or renovating ask for different sizes than businesses with stock or equipment.
- Local supply: which sizes do other facilities offer, which show as full online and what does a m² cost per size?
- Enquiries: if you already run a facility nearby or have a website before opening, record the size requested with every enquiry.
- Building: which sizes fit logically between columns, corridors and doors, and where could you split or merge later? Movable partition walls keep that option open.
- Phasing: fit out part of the building first with a broad spread of sizes, and complete the rest once you see which sizes are in demand.
A routine for reviewing your unit mix
How you divide your floor into sizes is not a one-off decision. A fixed rhythm lets you spot shifts in time without reacting to one busy month. A workable routine:
- Monthly: update occupancy in units and m², the waiting list, turned-away enquiries, move-ins and move-outs for each size.
- Quarterly: calculate the price per m², actual rent per m² and revenue per available m² for each size.
- Quarterly: adjust the price of sizes that are consistently full or empty, and record why.
- Yearly: assess physical changes such as splitting, merging or converting space, with the payback period alongside.
- After every change: compare occupancy and revenue by size with the period before.
