In short. Construction and infrastructure sites need power that changes with the work: site offices and tower cranes first, then batching plant and hoists, then building commissioning loads. A sound project plans generator capacity and temporary distribution by work stage, earths and protects every feeder, controls fuel and monitors running hours, and records what was delivered and tested so later claims stay within the evidence.
Power follows the programme
A high-rise in Kokapet, a metro extension, a highway flyover and a water pipeline all need temporary power, but their demand profiles differ and each changes as the work advances. Early stages may need only site offices, labour camp lighting, welding sets and a few pumps. Mid-programme brings tower cranes, passenger and material hoists, concrete pumps and batching plant. Near completion, the building’s own lifts, chillers and fire pumps need power for testing and commissioning, often before the permanent DISCOM connection is energised. Planning one generator for the whole programme usually means either a large set idling for months or a small set that is overloaded at the peak. A staged plan, typically with rental generators added and removed as stages change, matches capacity to need. Construction and infrastructure power and construction rental generators describe the options.
| Work stage | Typical loads | Power planning focus |
|---|---|---|
| Mobilisation | Site offices, camp, lighting, small tools | Single-phase balance, small set or rental |
| Substructure | Dewatering pumps, piling rigs, welding | Continuous pump duty, monsoon peaks |
| Superstructure | Tower cranes, hoists, concrete pumps, batching | Motor starting, step loads, distribution spread |
| Finishing and commissioning | Building lifts, HVAC, fire pumps, testing loads | Stable voltage, documentation, interface with permanent system |
Sizing for cranes and hoists
Tower cranes and hoists combine large motor starts with regenerative energy during lowering. A generator that easily carries the average site load can still dip enough during a hoist start for the crane’s controls to fault. Inverter-driven cranes reduce the starting step but add harmonic load, and regeneration back into a lightly loaded generator can drive frequency or voltage upward unless the crane has braking resistors. The crane supplier’s power data, not its nameplate kW, should set the requirement.
I = (P × 1000) / (√3 × V × PF)
I is feeder current in amperes, P the feeder load in kW, V the line voltage (415 V) and PF the power factor. Worked example (illustrative): a hoist feeder carrying 45 kW at 0.8 power factor draws about 78 A, so a 100 A protective device and cable rated for the load after grouping and ambient derating would be a starting point, then checked for voltage drop over the actual run length. A 150 metre run to the far end of a site can drop enough voltage to cause motor trouble even if the generator is correctly sized. See cable sizing.
Temporary distribution, earthing and protection
Most construction power incidents happen in distribution, not at the generator. One set often feeds several separate load areas through cables laid across a changing site, which is why distribution panels should be arranged by area or by purpose, with protection matched to each outgoing feeder and residual current protection for hand tools and site lighting. Every temporary system needs a defined fault return path: the generator neutral and frame earthed, earth continuity carried to each distribution board, and the earth electrode tested before energisation. Cable routes must be protected from vehicles, buried or raised where they cross haul roads, and reviewed as the site layout changes, since a route that was safe last month may sit under a new excavation. Distribution panels and earthing and neutral cover the details.
Fuel, maintenance and monitoring
Construction generators run long hours in dust, heat and vibration, so service intervals arrive sooner than on a standby set and air filters and radiators need more frequent attention. Fuel is both a cost and a control problem: telemetry that records fuel level, running hours and load lets the contractor see whether consumption matches work done and spot losses early. Planning refuelling around the programme also avoids the commonest site outage, which is simply a set running dry over a weekend.
Separating delivery from demonstrated performance
Mobilising and connecting a generator are project activities; they do not themselves prove that the site was continuously powered. A useful project record states the work stage, supported loads, distribution arrangement, tests performed before energisation, operating responsibilities and the duration of the deployment. No approved construction case is presented in this category; future cases will keep to what the records show. Related categories include manufacturing power projects and mining power projects.
Common mistakes
- Sizing one generator for the whole programme. It runs lightly loaded for months, then is overloaded when cranes and batching plant arrive.
- Running long feeders without a voltage drop check. Hoists and pumps at the far end of the site stall or trip even though the generator has spare capacity.
- Omitting residual current protection on tool and lighting circuits. A damaged cable in wet conditions becomes a shock hazard to workers.
- Leaving cable routes unchanged as the site evolves. Vehicles and new excavations damage cables that were safely routed at the start.
What to send us
Send the construction programme with expected stages and durations, the load schedule for each stage including crane, hoist and pump data, a site plan showing distances from the generator location to each load area, and access and fuel arrangements. Send a generator rental enquiry.
Questions engineers ask
Should a construction site buy or rent its generators?
Rental usually suits construction because demand changes by stage and ends at handover. Purchase can make sense for long programmes with a steady base load, or for contractors who move sets between sites. Compare total cost including maintenance, fuel management and the resale value.
What size generator does a tower crane need?
It depends on the crane’s hoist motor rating, its drive type and the other loads on the same set. The crane manufacturer’s power requirement and starting data should be used; a generic multiple of crane kW is not reliable.
How is a construction generator earthed?
The generator neutral and frame are connected to a tested earth electrode, and an earth conductor is carried to every distribution board so faults can clear through the protective devices. Residual current protection is added on final circuits for tools and lighting.
Can the construction generator be used to commission building services?
Yes, if its capacity, voltage stability and connection arrangement suit the commissioning loads. Commissioning lifts, chillers and fire pumps needs a more controlled supply than general site power, with documented connections and protection.
Generators by rating
- Under 15 kVA generators
- 15–50 kVA generators
- 50–125 kVA generators
- 125–250 kVA generators
- 250–500 kVA generators
- 500–1000 kVA generators
- 1–2 MVA generators
- 2 MVA and above generators
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.