Rooftop Solar for a UAE Warehouse or Factory: What to Check Before You Sign

Every commercial solar proposal leads with three numbers: system size in kWp, annual generation in kWh, and a payback in years. None of them is what kills projects. Projects die on a roof that cannot carry the load, on a waterproofing membrane with eight years left in it, or on a generation curve that peaks at noon while the plant runs its heaviest shift at six in the morning. Get those three right and the rest is procurement.

The roof decides the project before the panels do

Ask the structural question first, because the answer can cancel everything downstream. A ballasted system on a flat concrete roof adds dead load, typically in the order of 15 to 25 kg per square metre once ballast is counted — indicative only, until an engineer runs your numbers. A rail-mounted system on profiled metal sheet adds far less, often under 12 kg per square metre, but it transfers wind uplift into the purlins and their fixings rather than spreading it across a slab.

Two documents settle this: the as-built structural drawing with the design imposed load, and an assessment by a licensed structural engineer who has physically stood on the roof. A warehouse designed with headroom has room for an array; one built to the minimum, already carrying two chillers and a solar water heater someone added in 2011, may not — and nobody discovers that from a satellite image.

Wind is the load UAE buyers underestimate. Shamal events drive uplift on the windward edge and, worse, on the corners, far above the values mid-field. That is why competent designs set panels back from every edge and increase ballast or fixings in the corner and perimeter zones. If a layout shows modules running out to the parapet, ask which wind code was used and what design wind speed it assumed.

Waterproofing is a sequencing problem, not a technical one

The membrane under the array is the one part of the building you cannot reach again for twenty-five years. Three rules keep it from becoming an argument:

• Do not install onto a membrane with under ten years of remaining life. Re-roofing under a live array costs more than the array did.
• Penetrations are fine when detailed. A flashed and sleeved penetration by a roofing contractor with the membrane manufacturer's approval is not a leak. An unsleeved bolt driven through torch-on felt is.
• Fix the membrane warranty position in writing before work starts. Many are void once a third party fixes through them unless the original roofing contractor makes the penetrations. Bring them in at design stage.

On a sandwich-panel roof the fixing goes into the crown of the profile with the manufacturer's clamp, never through the valley where water runs.

Shading, orientation and the area you can genuinely use

Gross roof area is not array area. Subtract setbacks, plant and ductwork, walkways, smoke vents, access hatches and the maintenance clearance around each. On a typical UAE warehouse the usable fraction commonly lands between half and three-quarters of gross — indicative, and the only way to know yours is a marked-up drawing.

At mainstream module efficiencies, plan on roughly 5 to 6 square metres of roof per kWp for a coplanar layout on a metal roof, and meaningfully more on a flat roof, where tilted rows need spacing so they do not shade each other. That spacing is set by the low winter sun: rows spaced for a June sun angle self-shade for hours a day through December and January.

Shading in the UAE is rarely a tree. It is a parapet, a duct run, a lightning finial, a stair core, or the neighbouring warehouse that went up last year. Ask for a 3D shade study with full-year hourly simulation rather than a photograph, and for electrical mitigation where shade is unavoidable: independent MPPT strings, or module-level optimisers, so one shaded module does not drag its string down with it.

Orientation matters less at this latitude than people expect. Due south gives the highest yield per kWp; an east-west split on a flat roof gives a few per cent less per kWp, fits more kWp onto the same area, and produces a flatter curve that often suits an office load better. Your load decides, not a rule of thumb.

Match the generation curve to your load curve

This is the analysis most proposals skip, and the one that decides the economics.

Solar you consume on site is worth your full import tariff, including the fuel surcharge you avoid paying. Solar you export is worth whatever your utility's net-metering scheme says it is worth — in the UAE, a credit against future consumption, not a cheque. The commercial case turns on your self-consumption fraction.

So the first thing a serious bidder asks for is not a roof drawing. It is twelve months of electricity bills and, where the meter supports it, interval data. A cold store running compressors through the night and a printing plant on a single day shift can have identical annual kWh and completely different solar cases.

Load pattern	Self-consumption of a roof-filling array	What usually follows
Single day shift, weekdays only	High Monday to Friday, near zero at weekends	Size to the weekday midday base load, not the roof
Two shifts or a continuous process	High and stable all week	Roof area, not load, is the binding constraint
Cold store, night-heavy	Moderate; peak generation meets low load	Examine battery storage before oversizing
Office floors, weekdays	Good midday match, poor at weekends	East-west layout often beats due south

Indicative patterns only — your own interval data replaces every row of this table.

A useful test of a bidder: ask for simulated generation plotted over your measured load, hour by hour, for a typical week in each season, and for the self-consumption percentage that falls out of it. No plot means no analysis.

Indicative yield, and the losses that eat it

The UAE has the resource. Published figures put global horizontal irradiance across the Emirates broadly in the 1,900 to 2,300 kWh per square metre per year range, and well-designed rooftop systems here commonly report specific yields in the order of 1,600 to 1,900 kWh per kWp per year. Treat that as an indicative band, and as an output of a site-specific simulation rather than a promise.

Where that spread comes from:

• Heat. Module output falls as cell temperature rises, and a rooftop module in a Dubai July sits far above the 25°C at which its nameplate was measured. Arrays with little air gap behind them run hotter and lose more. This is the largest single gap between a brochure figure and a measured one; the module and inverter comparison guide explains how to read a temperature coefficient.
• Soiling. Dust is the defining PV loss in this region; published UAE field studies of modules left uncleaned for a year have measured severe output loss. Cleaning frequency is a design input, not an afterthought — it belongs in the O&M scope and in the yield model, and the model must state the soiling loss it assumed.
• Wiring, mismatch and inverter conversion losses. Normal, and already inside any competent simulation.
• Downtime. Rarely modelled, occasionally the largest loss of all. It belongs in the O&M conversation, with response times attached.

Performance ratio summarises all of the above, so ask for it explicitly — and treat a bidder who will not state assumed soiling and thermal losses as quietly inflating the yield.

What a proper proposal actually contains

A proposal thin enough to read in five minutes is thin enough to be wrong. Ask for all nine, and treat a missing one as a finding rather than an oversight:

1. A structural assessment, or a statement that one is a condition precedent, naming who pays.
2. A marked-up roof layout showing setbacks, plant, walkways and the real module count.
3. A single-line diagram down to the point of connection, naming the existing switchgear and its rating.
4. A shading study with full-year hourly simulation.
5. A yield model stating software, weather dataset, soiling loss, thermal model and degradation assumption.
6. Named equipment: module model and datasheet revision, inverter model, mounting system, cable and protection sizing.
7. The utility approval path with the enrolled consultant and contractor named — the subject of the Shams Dubai and net-metering guide.
8. An O&M scope: cleaning frequency, monitoring, response times, and exclusions.
9. A warranty schedule separating product, performance and workmanship, naming who carries each.

Comparing two quotes, line by line

Two proposals for the same roof rarely agree on kWp, and the cheaper one is usually cheaper for a reason you can find in under an hour. Normalise before you compare.

Line	Normalise to	The trap
System size	kWp DC and kW AC stated separately	Midday clipping from a high DC-to-AC ratio is a design choice, not a free upgrade
Yield	kWh per kWp per year, with stated soiling and thermal losses	Models built on different assumptions are not comparable
Modules	Exact model and datasheet revision	"590W Tier 1" names nothing anyone can be held to
Inverters	Model, quantity and MPPT string count	One central unit is a single point of failure for the roof
Mounting	Ballasted or mechanically fixed, and the wind code used	Ballast is load your roof carries for 25 years
Scope boundary	Who supplies DB modifications, containment, civils, crane and lifting	The cheapest quote often stops at the inverter terminals
Approvals	Who submits, who pays fees, who carries programme risk	"Client to obtain approvals" moves the utility process onto you
O&M	Years included, cleaning cycles per year, response time	A free first year is goodwill, not a service contract
Warranties	Whose paper it is, and who honours it inside the UAE	Covered in brand and warranty comparison

Scope boundary hides most of the price gap. Put each quote in its own column and force every row to be filled, including with "not included".

Who supplies, who installs, and who signs

Keep the commercial role and the regulatory role separate in your head, because they are separate in law.

CoHub holds a UAE General Trading licence. It supplies the equipment and delivers the project as your single commercial counterparty — one order, one proforma invoice, one tax invoice, one party to go back to. Design, installation, testing and utility approval are carried out by licensed, utility-enrolled contracting and consultancy partners working under CoHub's project management. CoHub is not itself a DEWA-enrolled contractor and is not a licensed engineering consultant, and the proposal names the partners who hold those roles.

That split matters on a roof: whoever seals the electrical drawings must be licensed to seal them, and whoever carries the equipment warranty should be who you bought from. Mixing the two turns a warranty claim into a three-way argument — the failure mode in the supplier selection guide.

What to send, and what comes back

Four things get a survey booked: twelve months of electricity bills, a roof drawing or plot number, the roof construction and rough age, and operating hours by day of week. Start at the commercial rooftop page, use the solar quote form, or send the bills through the RFQ form; the sales desk on WhatsApp takes photographs of them the same way. CoHub does not publish solar prices — a system is quoted after a survey, and anything priced without one is a guess with a decimal point in it. The rest of the section sits under solar and renewable energy.