How to Choose a Construction Site Generator

On a construction project, the demand for electricity is not constant. During excavation, a few pumps and lighting are enough; in the structural phase, the tower crane, concrete pump and welding machines come into play; during finishing works the load falls but the running time gets longer. The right site generator is one that meets this changing load profile, is easy to move around the site and can go for days without attention in harsh conditions. Below we take the questions to ask during selection one by one.

1. Split the loads by construction phase

Instead of a single total power, consider the peak of each phase separately:

Phase	Typical loads	Point to watch
Excavation and foundations	Drainage pumps, lighting, site office	Starting current of the pumps
Structural works	Tower crane, concrete pump, vibrators, welding machines	Simultaneous hoisting and slewing load of the crane
Finishing works	Hand tools, compressor, heaters, lighting	Long running time, low load
Site camp	Container offices, dormitories, canteen, air conditioning	Uninterrupted running through the night

Tower cranes and concrete pumps are the loads that put the most strain on a generator’s starting capacity. Crane manufacturers usually state the recommended minimum generator power in the operating manual; if this value is not checked and only the motor ratings are added up, the set may be undersized. For starting calculations for motor loads, see our article on generator sizing for electric motors.

2. Welding machines and hand tools

Many single-phase tools and welding machines are used on site. If these are distributed unevenly across the phases of a three-phase generator, one phase is overloaded while the others are lightly loaded. Practical recommendations:

• Split single-phase loads as evenly as possible across the three phases in the distribution board.
• Inverter welding machines generally work well with generators, but where there are many of them the harmonic effect should be assessed.
• If significant imbalance between phases is expected, the alternator rating should be selected accordingly.

3. Transport: trailer, skid or canopy

At the end of the project, the site generator moves to the next site. The way it is transported is therefore as important as its power:

• Trailer-mounted sets suit sites that move often and road construction work. We build the trailers in our own plant, and sets of every rating in our range can be supplied trailer-mounted. For details, see our trailer-mounted generators page.
• Canopied (sound-attenuated) sets protect the engine from dust, rain and impact. On sites close to residential areas, they reduce noise complaints.
• A base frame with lifting points and forklift pockets allows safe loading by crane or forklift.

4. Fuel: plan refuelling frequency from the start

The most common reason a generator stops on site is not a fault but running out of fuel. During selection, clarify the following:

• How many hours a day, and at what average load, will the set run?
• How often can fuel be delivered?
• Is the built-in tank sufficient, or is an additional external tank needed?

We explain with an example how to calculate tank capacity in our article on generator fuel tank sizing. Because water and sediment often get into fuel on construction sites, a pre-filter with water separator and regular draining of the tank bottom are useful.

5. Site conditions: dust, heat, cold

• Dust: the air filter clogs much faster than normal on a construction site. Shorten the filter check interval and, if possible, use a filter with a restriction indicator.
• Heat: in summer, the inside of a canopy working in the sun heats up. The front of the radiator and the canopy air inlets must not be blocked by stockpiled materials.
• Cold: on winter sites, an engine block heater and a battery charger are important for easy first starts; both are standard on our sets. For details, see our article on generator cold starting.

6. Electrical safety

A construction site is a high-risk working environment for electrical accidents. On the generator side, the following measures should be treated as mandatory:

• Earthing of the set and distribution boards, and measurement of the earth resistance
• Residual current protection on the output circuits
• Cables routed with protection across vehicle routes
• An emergency stop button that is easy to reach

Details on earthing are given in our article on generator earthing. The occupational health and safety legislation in force should be followed for the rules.

7. Buy or rent?

For needs of a few weeks limited to a single project, renting is usually more sensible. In Türkiye only, we offer a generator rental service from 30 to 1000 kVA on a daily, weekly, monthly and long-term basis. If your company runs several sites throughout the year, the option of buying should be assessed together with the annual running hours of the set and how maintenance is organised. Our article Rent or buy a generator? helps with the comparison.

Short checklist

• Has the peak load of each construction phase been determined separately?
• Has the generator power recommended by the manufacturer been checked for the tower crane and concrete pump?
• Will the set be trailer-mounted, or moved by crane?
• Are the refuelling interval and tank capacity compatible?
• Have earthing and residual current protection been planned?

If you send us your site’s load list and duration, we can determine the right power, type of transport and tank option together. For night work, take a look at our light towers as well.