Somebody has just asked you what generator you want on site, and you do not yet have an answer you can defend in a meeting.
That is who this page is for. Project engineers on a first Dubai posting, QSs told to get power sorted, villa owners in JVC or Al Furjan self-managing a build, fit-out managers in Al Quoz or Business Bay who have always let the MEP subcontractor decide, and free zone tenants in JAFZA or Dubai South whose authority has asked for a load schedule.
We load generators onto trucks at our Ras Al Khor yard most weeks of the year, and the same sizing mistakes come back with them. By the end of this page you will be able to build a load schedule, do the arithmetic, and read a spec sheet without bluffing.
One thing worth saying early. Most first-time renters ask for more kVA than they need, so this page will probably save you money.
If you only want the number rather than the method, go straight to what size generator a small Dubai site actually needs.
The Short Answer: How to Size a Generator in Six Steps
To size a generator, list every electrical load in kW, apply a diversity factor for what actually runs at the same time, check that the largest motor can start, convert kW to kVA by dividing by the power factor, derate for the site temperature, then round up to the next standard size.
- List every load in kW
- Apply an honest diversity factor to get running load
- Check the worst starting event
- Convert to kVA using power factor
- Derate for Dubai heat and site conditions
- Round up to the next standard rental size
One headroom, not four. This is the rule that saves the most money on this page. Beginners stack a diversity factor, a starting allowance, a heat derate and then a blanket 20 percent safety margin on top, and land two sizes too high. Each step in the list above does one job. Do not add a fifth cushion.
Want the fast answer for a small Dubai site instead of the method? That page has it.
Why Generator Sizing Goes Wrong on a First Project
The most common request our desk receives is for a set larger than the job needs. The second most common call is a trip that turns out to be a starting-sequence problem, not a capacity problem.
What happens if the set is too small
The physical event is quick and public. Voltage dips, the set trips on overload, the distribution board breaker goes, and somebody walks to the corner of the plot to press reset.
It is never one trip. It is a trip every time the same machine starts, so the crew begins working around it and productivity quietly halves without anybody logging a problem.
There is a wear angle too. Repeated deep voltage dips are hard on motors and on any electronics on site. The classic Dubai trigger is the welding set or the concrete mixer starting while the tower light and the site office AC are already running.
What happens if the set is too big
A diesel engine running lightly for weeks never reaches proper operating temperature. Unburnt fuel and soot build up in the exhaust side. That is wet stacking, and it is a real mechanical penalty, not a theoretical one.
Commercially it costs three ways: higher rental, more diesel burned per useful kWh, and a set that may need a load bank or a service before it will run clean again.
Oversizing also enlarges the logistics problem. Bigger footprint, heavier lift on offload, bigger cables, more fuel to store.
Here is the thing nobody in this industry says out loud: a supplier who always recommends the bigger set is optimising their own utilisation, not your programme. We would rather send the right set twice than the wrong set once.
From the yard. An interiors contractor working night windows in an occupied Business Bay building hired well above requirement “to be safe”. For four weeks the set ran at low load through long night shifts, the exhaust started showing wet, unburnt residue, and they were paying for capacity they never used, in rent and in diesel. We explained wet stacking, moved them down to a correctly sized set for the remainder, and agreed a sensible minimum loading for the shift. Oversizing is not the safe option. It is the expensive option with a mechanical penalty attached.
The two mistakes that are specific to Dubai
Sizing at the nameplate rating. A set that was correct in January struggles in July, because the nameplate is a laboratory number and your site is not a laboratory.
Sizing from an equipment list rather than a programme. Plant that will never run in the same week gets added together.
Dust and airflow compound both. A set boxed into a corner of a walled villa compound in Al Barsha recirculates its own hot air and behaves as though it is in an even hotter ambient than the forecast says.
From the yard. A logistics operator doing a racking and mezzanine install in Dubai Investment Park built their request from an asset list rather than a programme, and asked for a set several sizes larger than the job needed. Half the plant on that list was not even scheduled for the same weeks. We asked for the programme, marked which loads were live in each stage, and rebuilt the number from the busiest stage. The set that went out was materially smaller, and they paid less in rent and much less in diesel. Size the busiest realistic minute, not the equipment register.
The Electrical Basics You Actually Need
This is the minimum vocabulary, not an engineering course. Every definition below is followed by what it means for you in practice.
kW, kVA and power factor
kW is the real work the load does. kVA is the total the alternator has to supply, including the reactive part it never converts into work.
Both directions of the formula:
kW = kVA x power factor kVA = kW / power factor
Most diesel generator sets are rated at 0.8 power factor, so a 100 kVA set delivers 80 kW.
The practical consequence matters. If your load list is in kW and the quotes are in kVA, you are comparing two different things until you convert. Divide your kW by 0.8.
Watch the reverse trap too. Some tool nameplates state kVA or amps rather than kW. Never mix units inside one column of your schedule.
One more thing worth knowing. Lots of induction motors and older welding sets pull a site’s power factor below 0.8, which raises the kVA you need for the same kW.
Single phase or three phase, and what 230 V and 400 V mean here
UAE site equipment expects 230 V single phase and 400 V three phase at 50 Hz. The relationship is simpler than it sounds. 400 V three phase is measured line to line. 230 V is line to neutral. The same set usually offers both.
The decision rule: if everything on your list is hand tools, lighting and a site office, single phase output may be enough. The moment there is a three phase motor, a hoist, a passenger lift, a chiller or a larger welding set, you are on three phase.
Three phase is better for motors anyway. Smoother torque, smaller cables for the same power, and less voltage dip on start.
If your equipment was bought or shipped from a 60 Hz or 110 V market, it will not run correctly here without a transformer or a different spec. This catches events and exhibition companies regularly.
And one free improvement: on a three phase set, spread the single phase loads across all three phases. Hanging every socket off one phase makes a correctly sized set behave like an undersized one.
Amps, and why your electrician cares about them more than kVA
Two formulas, both worth keeping:
Three phase: amps = (kVA x 1000) / (1.732 x 400) Single phase: amps = (kVA x 1000) / 230
Worked: a 30 kVA set at 400 V three phase gives (30 x 1000) / (1.732 x 400) = 43 A per phase.
That number is why it matters. Cable size, breaker size and distribution board rating are all chosen from amps, not from kVA.
The shortcut to remember: at 400 V three phase, multiply kVA by about 1.44 to get amps.
Running load, starting load and step load: three different numbers
Running load is what is drawn once everything is up and working. Starting load is the surge when a motor switches on. Step load is how much load you throw at the set in one go.
Here is the teaching point that changes how people size. A set can often handle a large starting surge that it could never carry continuously, because the surge lasts a second or two.
Which makes step loading a free lever. Staggering start-up by 20 or 30 seconds per machine can let a smaller set do the same job. Almost nobody plans this, and it costs nothing.
Transient behaviour is standardised, incidentally. Under ISO 8528-5, a class G3 set is expected to hold frequency within roughly minus 7 to plus 10 percent, recovering within about 3 seconds, and voltage within roughly minus 15 to plus 20 percent, recovering within about 4 seconds. That is why the lights dim and come back rather than going out.
Still not sure whether your site is single phase or three phase? Send us a photo of the rating plates and we will tell you what you are dealing with, no obligation and no quote attached. WhatsApp 056 857 8181.
Step One: Build Your Load Schedule
What a load schedule is, and why it is the whole job
A load schedule is a single table listing every electrical item, its rating in kW, how many of them, whether it is a motor, and when in the programme it runs.
The principle that saves the most money: you are sizing for the busiest realistic minute of the busiest day, not for the sum of everything you own.
Get the numbers from the nameplate or rating plate on each machine, from the hire company’s spec sheet, or from the supplier’s data sheet. Never from memory.
Convert everything to kW before you sum. If a plate shows amps, convert first.
The fillable load schedule table
| Item | Qty | Rating each (kW) | Total (kW) | Motor? | Starter type | Runs during which stage | Same time as others? |
|---|---|---|---|---|---|---|---|
| Site office split AC | 2 | 2.2 | 4.4 | Y | DOL | All stages | Y |
| Tower light | 3 | 1.0 | 3.0 | N | n/a | Night only | Y |
| Connected load total | |||||||
| Simultaneous running load |
Fill the last column honestly, because that column is where your diversity factor comes from. Everything else is bookkeeping.
Loads beginners forget, in the order we usually have to remind people: site office and its AC, welfare and the drinking water cooler, security lighting overnight, the water pump, the curing pump, the hoist, phone and laptop charging, CCTV, the compressor for the sprayers, and the drying or dehumidification kit on a fit-out.
Fill this table in, screenshot it, and WhatsApp it to 056 857 8181. We will check your totals, your diversity and your starting load, and reply with what we would actually send. It costs nothing and it is not a quote.
How to choose an honest diversity factor
Diversity is the ratio between what you own and what is genuinely energised at the same moment.
The industry rule of thumb reported across the market is 0.7 to 0.8 on a typical mixed site. That is a rule of thumb, not a law, and treating it as a law is how people get it wrong in both directions.
The better method takes ten minutes. Go stage by stage through your programme: excavation, structure, blockwork, first fix, second fix, snagging. Mark which loads are live in each stage. The highest stage total is your running load.
Two guardrails. Do not apply a diversity factor below about 0.6 unless you can point at the programme line that justifies it. And never apply diversity to a load that is genuinely continuous, such as a dewatering pump or a cold store.
One exception worth knowing. On a mall or office fit-out with a fixed night window, everything really does run at once, because there are only six hours to work. Diversity there is close to 1.0.
Step Two: Handle the Starting Load Without Oversizing
Why motors are the whole problem
A motor at the instant of switch-on draws far more current than it does when running, because it has not yet built back EMF.
The published figure: motor and transformer inrush is typically around six times full load current, and some high efficiency motors can approach roughly double that.
But there is a counterweight from the same source. Modern sets can supply around three times nominal current briefly to cover inrush peaks, so you do not size the whole set on inrush current.
The sizing rule: check that the set can start the single largest motor while the rest of the running load is already on. You do not add up every motor’s starting surge.
Starting multipliers by starter type
| Starter type | Typical starting demand | What it means in practice |
|---|---|---|
| Direct on line (DOL) | About 3 to 4 times the motor rating | Cheapest starter, hardest on the generator, common on small pumps and compressors |
| Star-delta | About 1.5 to 2 times | Common on medium motors, halves the hit but adds a second transition surge |
| Soft starter | About 1.3 to 1.8 times | Ramps up, much kinder to the set, common on newer plant |
| Variable speed drive (VSD) | About 1.1 to 1.3 times | Gentlest start, but adds harmonics the set has to tolerate |
Those bands are typical industry figures. Read the motor plate, or ask the plant supplier for the actual starting kVA, wherever the motor is large relative to the set.
The check itself is one line of arithmetic. Running load minus the largest motor’s running kW, plus that motor’s starting demand, must sit inside what the set can supply for a few seconds.
And the fix that costs nothing: start the big motor first, before the site is fully loaded, or stagger the start-ups.
Do not double count. If you have applied a starting multiplier, do not then add a blanket 20 percent safety margin. The starting check is the margin.
From the yard. An independent villa builder in JVC hiring power for the first time had sizing that was fine on paper. Then a compressor borrowed from another site was started direct on line at the same moment the mixer was running, and the set tripped repeatedly. The customer assumed the generator was faulty. We attended, found no fault, and changed the sequence of switch-on so the compressor started before the site was fully loaded. The trips stopped without changing the set. Starting load and running load are different problems, and the order you switch things on is free capacity.
Step Three: Convert to kVA and Read the Rating Correctly
Turning your kW into kVA
Divide your running kW by 0.8.
Worked: 24 kW of running load divided by 0.8 is 30 kVA.
If your site power factor is genuinely worse than 0.8, meaning lots of old induction motors and no correction, the kVA figure rises for the same kW.
Prime, standby, continuous: the rating changes the number on the canopy
Here is why this matters before anything else. The same physical set can be advertised as a prime rated machine or a standby rated machine, and the standby number is higher. Comparing a standby kVA against a prime kVA is comparing two different promises.
| Rating | Typical annual hours | Average load limit | Overload allowed | Right use on a Dubai site |
|---|---|---|---|---|
| Emergency standby (ESP) | Up to about 200 hours per year | About 70 percent of the standby rating over 24 hours | None | Backup behind a DEWA supply that is already live |
| Limited time prime (LTP) | Up to about 500 hours per year | Up to 100 percent during operation | None | Short, defined campaigns |
| Prime (PRP) | Unlimited hours, allowing for servicing | About 70 percent of the prime rating over any 24 hours | About 10 percent, roughly 1 hour in 12, limited annually | The normal choice for a site running as the only power source |
| Continuous (COP) | Unlimited hours | Constant 100 percent load | None | Constant base load, rarely a construction hire |
Those definitions come from ISO 8528-1.
The takeaway for a site with no mains: ask for the prime rating, and size against that number.
Note what the 70 percent average load line is telling you. A prime rated set is designed to average around 70 percent of its rating over a day. That is another reason not to buy a set you will run at 25 percent.
When comparing two quotes, check both are quoting the same rating class before you compare the kVA.
How to read a generator spec sheet line by line
A spec sheet gives you: prime kVA and kW, standby kVA and kW, voltage and phase configuration, frequency, power factor, engine make and model, alternator make, fuel tank capacity in litres, fuel consumption at 50, 75 and 100 percent load, sound level in dBA at a stated distance, dimensions and dry weight, control panel type, breaker rating in amps, and the derate curve or reference conditions.
Four lines decide most hires: prime kVA, tank litres, consumption at 75 percent load, and dBA at 7 m.
Weight and dimensions decide the offload method and whether the set fits through your site gate, which is worth checking before delivery day rather than on it. What happens on delivery day covers that side, and our transport runs under RTA rules.
A canopied set carries a sound rating and an open set does not. For Dubai Municipality noise limits and where a canopy is mandatory rather than preferable, see the small site sizing guide.
The reference conditions line is the one that matters most here, which brings us to the next step.
Step Four: Derate for Dubai Heat, Dust and Airflow
Why the nameplate is a laboratory number
Manufacturers rate sets at reference site conditions. Your site is not those conditions.
Under IEC 60034-1, AC generators are designed for site conditions up to about 1000 m altitude and ambient air up to about 40 degrees C for industrial applications.
Above that, the standard is explicit. Where maximum ambient sits between 40 and 60 degrees C, the permitted temperature rise limits are reduced by the amount the ambient exceeds 40 degrees C, achieved by lowering the continuous rating. In plain English: the set is allowed to make less power.
Dubai summer afternoon shade temperatures routinely exceed that 40 degree reference, and the air immediately around a canopy in a walled compound is hotter still.
The derating rules of thumb, and where they come from
These are typical figures with their sources named. The manufacturer’s derate curve on your spec sheet always overrides a rule of thumb.
- Alternator derate: about 3 percent for every 10 degrees C above 40 degrees C
- Altitude derate: about 1 percent per 100 m above 1000 m, which is largely irrelevant in Dubai since we sit near sea level
- Air density context: falls roughly 1 percent per 100 m of elevation and roughly 0.3 percent per degree C of temperature rise
UAE rental suppliers commonly quote a 10 to 15 percent climate allowance above 40 degrees C. Treat that as a planning allowance rather than a calculated derate.
Apply one derate allowance and stop. Do not add a second safety margin on top of it.
The site conditions that derate a set more than the weather does
Airflow. A set pushed against a wall or into a corner recirculates its own hot exhaust air. Leave clear space on the radiator discharge side, never blow hot air into a boundary wall, and confirm the manufacturer’s minimum clearances.
Dust. Sites in Ras Al Khor, Al Quoz, DIP and Jebel Ali clog radiator cores and air filters fast. A blocked core is a thermal derate whether or not anybody calls it one.
Sun. A set in full afternoon sun with no shade runs hotter than the same set on the shaded side of a building. Position costs nothing and buys you output.
Fuel and heat. Watch condensation and fuel quality on long stands, and ask who is responsible for fuel filtration.
From the yard. A villa renovation contractor working inside a walled Al Barsha compound placed the set with its radiator discharge a short distance from the boundary wall, to keep the driveway clear. In summer it recirculated its own hot air and started shutting down on high temperature in the afternoons. Nobody had touched the load. We repositioned the set so the discharge was clear and shaded the canopy from the afternoon sun, and the shutdowns stopped. The ambient temperature that matters is the air the set is actually breathing, not the forecast.
Fill in the load schedule above, send it to us, and our rental desk will check the maths before you commit to anything. We will tell you if you have oversized. Most first-time renters have. Call 056 857 8181 or 054 581 9331, or WhatsApp the table straight across. Delivery and pickup are included in every rental, so the figure you agree is the figure you plan around.
Step Five: Two Worked Dubai Examples, Start to Finish
Every intermediate number is shown. Follow the same six steps both times and you will see the method is repeatable rather than bespoke.
Example one: a warehouse fit-out in Dubai Investment Park
Racking installation and mezzanine work in a shell unit where the landlord’s supply is not yet energised in the tenant’s name. Six week programme, day shift.
| Item | Qty | Rating each (kW) | Total (kW) | Motor? | Starter | Runs when |
|---|---|---|---|---|---|---|
| Scissor lift chargers | 2 | 1.5 | 3.0 | N | n/a | Overnight only |
| Air compressor | 1 | 2.2 | 2.2 | Y | DOL | Occasional |
| Magnetic drill and power tool circuit | 1 | 3.0 | 3.0 | Mixed | n/a | All day |
| Temporary lighting | 1 | 4.0 | 4.0 | N | n/a | All day |
| Site office split AC | 1 | 2.5 | 2.5 | Y | DOL | All day |
| Water cooler and welfare | 1 | 1.5 | 1.5 | N | n/a | All day |
| Welding set | 1 | 5.0 | 5.0 | N | n/a | Intermittent, peak stage |
Step 1. Connected load: 3.0 + 2.2 + 3.0 + 4.0 + 2.5 + 1.5 + 5.0 = 21.2 kW
Step 2. Diversity from the programme. The busiest stage is mezzanine steel and welding. Live at that point: lighting 4.0, office AC 2.5, welfare 1.5, power tools 3.0 and the welding set 5.0. The chargers are overnight only. The compressor is occasional and does not coincide with peak welding.
Simultaneous running load: 4.0 + 2.5 + 1.5 + 3.0 + 5.0 = 16.0 kW
Overnight the picture is entirely different, at roughly 4 kW of chargers and security lighting, so the day shift sets the size.
Step 3. Starting check. The largest motor is the 2.2 kW compressor on DOL, so 3 to 4 times gives roughly 6.6 to 8.8 kW of starting demand. It does not run at peak, so the worst case is starting it against roughly 11 kW of other load. Comfortably inside a set’s brief surge capability.
Step 4. Convert to kVA: 16.0 / 0.8 = 20 kVA of running demand
Step 5. Loading and derate. A prime rated set wants to average around 70 to 80 percent. At 75 percent loading: 20 / 0.75 = 26.7 kVA. Apply a 10 percent Dubai heat allowance: 26.7 / 0.9 = 29.6 kVA
Step 6. Round up: 30 kVA.
What we would actually send. A 30 kVA canopied set, three phase, with a distribution board and correctly rated tails, plus an earth rod. Canopied because the unit is inside a leased shell and the neighbours are working tenants. Note the charger load: scissor lift chargers are a genuine overnight draw that beginners leave off the schedule entirely, and if you are hiring scissor lift hire alongside the generator, put them on the list. The same applies to any forklift hire for a small warehouse charging in the same unit.
Example two: a villa plot in JVC at first fix
Independent villa build, first fix stage, no DEWA builder supply yet, residential neighbours on both sides, day work only under the summer midday break rules.
| Item | Qty | Rating each (kW) | Total (kW) | Motor? | Starter | Runs when |
|---|---|---|---|---|---|---|
| Concrete mixer | 1 | 2.2 | 2.2 | Y | DOL | Pour days |
| Water pump | 1 | 1.5 | 1.5 | Y | DOL | Occasional |
| Bar bending and cutting circuit | 1 | 3.0 | 3.0 | Y | DOL | All day |
| Tower lighting | 3 | 1.0 | 3.0 | N | n/a | Night only |
| Site office AC | 1 | 2.2 | 2.2 | Y | DOL | All day |
| Curing pump | 1 | 1.1 | 1.1 | Y | DOL | Occasional |
| General power tools | 1 | 3.0 | 3.0 | Mixed | n/a | All day |
Step 1. Connected load: 2.2 + 1.5 + 3.0 + 3.0 + 2.2 + 1.1 + 3.0 = 16.0 kW
Step 2. Diversity. Busiest stage is a pour day: office AC 2.2, power tools 3.0, bar bender 3.0 and mixer 2.2. Tower lighting is night only. The water and curing pumps are occasional and do not coincide with the pour peak.
Simultaneous running load: 2.2 + 3.0 + 3.0 + 2.2 = 10.4 kW
Step 3. Starting check, and why sequence matters. The mixer is the largest motor at 2.2 kW on DOL, so roughly 6.6 to 8.8 kW of starting demand.
Started last, with 8.2 kW already running, the transient peak is roughly 17 kW. Tight.
Started first, before the site loads up, the peak is roughly 11 kW. Comfortable.
Same machine, same set, no extra cost. That is step loading doing real work.
Step 4. Convert to kVA: 10.4 / 0.8 = 13 kVA of running demand
Step 5. Loading and derate: 13 / 0.75 = 17.3, then 17.3 / 0.9 = 19.2 kVA
Step 6. Round up: 20 kVA.
Now the comparison that matters. Suppose you had skipped diversity and simply summed the connected load. 16.0 kW / 0.8 = 20 kVA, then 20 / 0.75 = 26.7, then the derate gives 29.6, and you round up to 30 kVA.
Same villa. Same tools. A 30 kVA set instead of a 20, paid for in rent every week and in diesel every hour, for the entire build. That single ten-minute exercise with the programme is the difference.
What we would actually send. A 20 kVA canopied set. Canopied is not optional here, because you have neighbours on both sides. For the actual noise limits that apply and when they bite, see the small site sizing guide, and if you also need groundworks on the plot, mini excavator hire for villa projects covers that side.
Once you have your number, compare your number against typical small site sizes.
Generator Sizing Chart: kVA, kW and Amps at a Glance
The formulas, so you can extend the table yourself:
- kW = kVA x 0.8
- Three phase amps at 400 V = kVA x 1.44
- Single phase amps at 230 V = kVA x 4.35
| kVA | kW at 0.8 pf | Amps at 400 V 3ph | Amps at 230 V 1ph | Typical example loads |
|---|---|---|---|---|
| 10 | 8 | 14 | 44 | Hand tools, lighting, welfare |
| 15 | 12 | 22 | 65 | Above plus a small pump and site office AC |
| 20 | 16 | 29 | 87 | Above plus a bar bender and a small mixer |
| 25 | 20 | 36 | 109 | Above plus a compressor |
| 30 | 24 | 43 | 130 | Above plus an intermittent welding set |
| 45 | 36 | 65 | 196 | Multiple motors plus continuous welding |
| 60 | 48 | 87 | 261 | Hoist, larger pumps, mixed plant |
| 80 | 64 | 115 | 348 | Heavier mixed plant with concurrent motors |
| 100 | 80 | 144 | 435 | Larger site distribution |
| 125 | 100 | 180 | 543 | Larger site distribution |
| 150 | 120 | 217 | 652 | Larger site distribution |
| 200 | 160 | 289 | 870 | Larger site distribution |
This chart converts units. It does not size your site. The sizing comes from your load schedule.
Fuel, Tank Size and How Long the Set Will Actually Run
Estimating consumption
The rule of thumb, derived from published consumption charts: roughly 0.28 to 0.30 litres of diesel per kW of output per hour at full load.
Here is the derivation so you can trust it rather than take it. A 20 kW set at full load consumes about 1.6 US gallons per hour, which is about 6 litres per hour, which works out at about 0.3 litres per kW per hour.
Now the caveat that matters more than the rule. Consumption scales with load, not with the badge on the canopy. A set at 50 percent load uses considerably less than half again of the full load figure, and the spec sheet’s own consumption line at 50, 75 and 100 percent load beats any rule of thumb.
Worked from example one: 16 kW of running load at 0.3 litres per kW per hour gives roughly 4.8 litres per hour.
Ask for the manufacturer’s consumption figures with your quote. A supplier who cannot produce them is guessing.
Runtime planning and refuelling in Dubai
The sum is simple: usable tank litres divided by litres per hour equals hours before somebody has to refuel.
Treat the tank as usable down to about a quarter, not to empty. Running a diesel tank dry pulls sediment and air into the system.
Worked: a 100 litre tank, usable down to a quarter, gives 75 litres. At 4.8 litres per hour that is roughly 15.6 hours of running.
Now make it a scheduling problem rather than a fuel problem. If your runtime lands mid-shift, somebody stops work to refuel. Size the tank or the bunkering plan so refuelling happens between shifts.
The Dubai practicalities to settle before delivery: who supplies the diesel, whether the rental includes a starting tank of fuel, whether a bowser can physically reach the set on your plot, and gate access hours. Fuel delivery here is a scheduled logistics job, not an on-demand one.
Ramadan hours and the summer midday work break change when the site is live, which changes the runtime plan. So does hire length, and daily, weekly and monthly hire each suit a different shift pattern.
Bunded tanks, drip trays and spill kits are what a landlord, a free zone authority or a main contractor’s HSE officer will ask about, and Dubai Civil Defence requirements can apply where fuel is stored on site. Ask who provides them.
From the yard. A facilities team running a planned shutdown in a Jebel Ali warehouse calculated runtime from the full load consumption figure but never checked it against the actual shift length or the gate access hours. The tank reached its practical limit part way through the shift, and a fuel delivery could not get through the gate at that hour. We recalculated runtime from the real load, moved the refuelling slot to between shifts, and confirmed gate access times with the site before the next visit. Runtime is a scheduling problem before it is a fuel problem.
Fuel cost is usually bigger than the rental
Over a month of continuous running, diesel typically outweighs the hire line.
The method: litres per hour x hours per day x days x price per litre. UAE pump prices are revised monthly, so use the current figure rather than one from an article.
That arithmetic is the real financial reason not to oversize. You pay for the extra capacity twice, once in rent and once in fuel.
For what the hire line itself costs, see what generator hire actually costs in Dubai.
What Goes With the Generator: Cables, Distribution Boards and Earthing
Cable and tails
The correct set with undersized tails is still an undersized system, and that is a fire risk rather than a nuisance.
The reasoning chain runs: amps from your kVA conversion, then cable selected by a competent electrician for that current, the run length, the installation method and the ambient temperature, which in Dubai derates cable as well as generators.
We do not publish cable sizes here, deliberately. Cable selection is the electrician’s responsibility under the applicable regulations, and a table on a rental page would be misused.
What to ask your supplier: what length and size of tails come with the set, and what happens if the set has to sit 40 m from the distribution board because of access.
And one practical point that turns up in every HSE inspection: cables crossing a haul route need ramps or ducting.
The temporary distribution board
A temporary distribution board splits the supply into protected circuits, provides the sockets the site actually uses, and holds the RCDs and breakers.
Your checklist: correct incoming rating in amps, RCD protection on socket circuits, a weatherproof and dust-rated enclosure, the right socket types and voltages for the tools on site, and clear labelling.
Confirm whether the board is part of the hire or a separate item, and who is responsible for its inspection and test certificate.
DEWA publishes regulations for electrical installations in Dubai, and main contractors, Trakhees and free zone authorities commonly require a third party inspection of a temporary installation. Check the current requirements for your site rather than assuming.
Earthing
A generator supplying a site is a separate source, and its installation needs a proper earthing arrangement, usually including an earth electrode at the set, with the earth connection tested rather than assumed.
The failures we see in practice are consistent: no earth spike driven at all, a spike driven into loose backfill so the resistance is meaningless, the earth cable left disconnected after a set is repositioned, and an RCD that has never been tested with a test button let alone an instrument.
Ask two questions before delivery. Does the set come with an earth rod and lead, and who is signing off the earth test.
To be clear about the boundary: this is a licensed electrician’s work. Our handover briefing covers what the set provides. It does not cover your site installation design, and we will not pretend otherwise.
From the yard. A signage and fabrication company in Al Quoz moved their set a few metres during a yard reorganisation. The tails were reconnected. The earth lead to the rod was not. It was found during a routine visit, not by anyone on site. We reconnected it, had the arrangement checked, and made it a fixed item on the handover briefing: if the set moves, the earth moves with it and gets checked again. Earthing is the part of the installation that fails silently, which is exactly why it needs a named owner.
How Dream Way Helps You Get This Right
Send us the filled load schedule on WhatsApp and our desk will check the arithmetic and tell you if you have oversized, before any quote is written. Nobody else in this market offers that, and it costs you nothing.
- Delivery and pickup included in the rental package
- Daily, weekly and monthly hire
- Trained and certified operators available on request
- Basic operational training and a safety briefing at handover
- Regular equipment inspection
- 24/7 availability across Dubai, Sharjah and the Northern Emirates, plus Abu Dhabi
Government of Dubai licensed, RTA Dubai registered, Federal Tax Authority VAT registered. Prices exclude 5 percent VAT unless stated. See our full equipment rental fleet for what else goes on the same delivery.
Ready to get power on site? Dream Way Equipment and Machinery Rental supplies generators across Dubai, Sharjah, Abu Dhabi and the Northern Emirates, on daily, weekly and monthly hire, with delivery, pickup and a handover safety briefing included, and trained operators available on request. We are available 24/7 from our yard in Ras Al Khor Industrial Area 2. Call 056 857 8181 or 054 581 9331, WhatsApp us your load schedule, or email sales@dreamwayrental.com. Government of Dubai licensed, RTA registered and VAT registered with the Federal Tax Authority. Prices exclude 5 percent VAT.
Frequently Asked Questions
How do you size a generator step by step? List every load in kW, apply a diversity factor for what genuinely runs at the same time, check the largest motor can start against that running load, divide by the power factor to get kVA, apply one heat derate, then round up to the next standard size. One headroom, not four.
What is the difference between kVA and kW? kVA is apparent power, the total the alternator must supply. kW is real power, the actual work your tools do. Generators are usually rated at 0.8 power factor, so a 100 kVA set delivers 80 kW. If your load list is in kW and quotes are in kVA, convert before comparing anything.
How do I convert kVA to kW? Multiply kVA by the power factor. At the standard 0.8, a 30 kVA set gives 24 kW. Going the other way, divide kW by 0.8, so 24 kW of load needs 30 kVA of set. Keep every entry in your load schedule in the same unit before you total the column.
How many amps is a 30 kVA generator? Roughly 43 A per phase at 400 V three phase. The formula is amps = (kVA x 1000) / (1.732 x 400), so (30 x 1000) / 692.8 = 43.3 A. The shortcut is to multiply kVA by about 1.44. Your electrician sizes cables and breakers from that number, not from kVA.
Do I need a single phase or three phase generator? Single phase may cover hand tools, lighting and a site office. The moment you have a three phase motor, a hoist, a chiller or a larger welding set, you need three phase. If you take three phase, spread your single phase loads across all three phases, because an unbalanced set behaves like an undersized one.
What is the difference between prime power and standby power? Prime rating is for continuous site use as the only power source, with about 70 percent average load over 24 hours and around 10 percent overload capability. Standby is for backup behind a live supply, limited to roughly 200 hours a year with no overload. Compare two quotes on the same rating class.
How much does heat reduce a generator’s output in the UAE? Reference conditions under IEC 60034-1 run to about 40 degrees C ambient. Above that, alternator output typically derates around 3 percent per 10 degrees C as a rule of thumb, and UAE suppliers often plan a 10 to 15 percent climate allowance. The manufacturer’s derate curve on the spec sheet always overrides a rule of thumb.
How much diesel does a generator use per hour? Roughly 0.28 to 0.30 litres per kW of output per hour at full load, as a rule of thumb. So 16 kW of running load burns around 4.8 litres per hour. Consumption follows load rather than the badge, and the spec sheet’s figures at 50, 75 and 100 percent load are authoritative.
Can I run a generator smaller than my total connected load? Yes. That is the entire point of diversity. Provided your simultaneous running load and your starting check both pass, a set sized well below your connected total is correct, not risky. Sizing to connected load is the single most expensive mistake first-time renters make.
What size generator do I need for a small site in Dubai? That depends on your load schedule, which is what this page teaches you to build. For typical bands by site type, along with pricing, permits and noise rules, see our small site sizing guide.
Does a rented generator come with cables and a distribution board? It varies by supplier and by hire, so ask rather than assume. Confirm what length and size of tails are included, whether the distribution board is part of the hire or a separate item, whether an earth rod and lead come with the set, and who signs off the earth test.
Can I hire a generator for one day in Dubai? Yes, daily hire is available, with delivery and pickup included in the rental package. Whether daily is the cheapest option depends on how many days you actually need it and how many separate site visits are involved, which daily, weekly and monthly hire works through properly.