What Size Generator Do You Need For A Construction Site?
Key takeaways:
- Most construction sites use generators in the 20kVA to 100kVA range, depending on equipment, site size, and project requirements
- Welders, compressors, pumps, and other high-demand equipment can significantly increase generator size requirements
- Startup loads must always be considered, as some tools and machinery need more power when starting than when running
- Many construction sites require three-phase power for larger tools, machinery, and temporary site infrastructure
- Choosing the correct generator size helps reduce downtime, improve reliability, and control fuel costs on site
- Construction sites with multiple trades working at the same time may need additional generator capacity
- Allowing spare capacity can help support changing site requirements as the project progresses
Choosing the right generator for a construction site is critical for productivity, safety, and project efficiency.
A generator that is too small may struggle to power tools and equipment. A generator that is too large can increase fuel costs and operating expenses unnecessarily.
The ideal construction site generator depends on the equipment being used, the number of workers on site, startup power requirements, and whether single-phase or three-phase power is required.
What Affects Construction Site Generator Size?
Every construction project is different.
A small residential renovation has very different power requirements compared to a large commercial development.
When sizing a construction site generator, consider:
- Number of tools operating simultaneously
- Site sheds and offices
- Lighting requirements
- Air conditioning
- Pumps
- Compressors
- Welders
- Battery charging stations
- Temporary site facilities
Understanding how generator sizing works is essential. If you're unfamiliar with electrical power calculations, read our guide on kVA, kW, amps and watts explained.
Typical Equipment Found On Construction Sites
The equipment being used will largely determine the generator size required.
| Equipment | Typical Power Demand | Approximate Power Draw |
|---|---|---|
| Site office | Low demand | 1–5kW |
| Lighting towers | Low to medium demand | 1–6kW |
| Power tools | Low demand | 0.5–3kW |
| Battery charging stations | Low demand | 0.5–2kW |
| Air compressors | Medium demand | 5–20kW |
| Water pumps | Medium demand | 2–15kW |
| Concrete mixers | Medium demand | 3–10kW |
| Welders | Medium to high demand | 5–30kW+ |
| Large site facilities | High demand | 20–100kW+ |
Startup loads are often much higher than running loads, particularly for compressors, pumps, and welders.
Every construction site has different power requirements depending on the equipment being used, site layout, operating hours, and future expansion plans. Before selecting a generator, it's important to understand your total site load and how power demand may change throughout the project. Our guide to commercial generator power planning explains how to assess site requirements and build a reliable temporary power strategy.
Small Construction Site Example
A small residential construction project may require power for:
- Site office
- Charging stations
- Small power tools
- Lighting
In many cases, a 20kVA generator provides sufficient power for these applications.
To better understand the capability of this size generator, see our guide on what will a 20kVA generator run.
Medium Construction Site Example
A medium-sized project may require:
- Multiple site sheds
- Lighting towers
- Compressors
- Several power tools operating simultaneously
In these situations, a 50kVA generator is often a popular choice.
A 50kVA generator typically provides approximately 40kW of usable power and offers greater flexibility for changing site requirements.
Learn more in our guide on what will a 50kVA generator run.
Large Commercial Construction Site Example
Large commercial developments often require:
- Multiple site offices
- Large compressors
- Welders
- Cranes
- Extensive lighting
- Temporary site infrastructure
These projects frequently require generators of 100kVA or larger.
In some cases, multiple generators may be synchronised to provide additional capacity and redundancy.
Construction sites should ensure temporary power systems are installed and operated in accordance with applicable electrical safety requirements.
Single Phase vs Three Phase Construction Generators
Many construction sites require three-phase power.
Three-phase generators are commonly used for:
- Welders
- Large compressors
- Industrial equipment
- Pumps
- Commercial construction equipment
Single-phase generators are generally suitable for:
- Site sheds
- Small tools
- Lighting
- Basic temporary power
- Selecting the wrong phase configuration can create operational issues and equipment compatibility problems.
Common Construction Site Generator Sizing Mistakes
Only Calculating Running Loads
Startup currents can significantly exceed normal operating loads.
Failing to account for surge demand can result in overloads and power interruptions.
Choosing The Cheapest Generator
The lowest-cost option is not always the most suitable solution.
Fuel efficiency, reliability, runtime, and support services should all be considered.
Underestimating Future Requirements
Construction projects often evolve.
Additional equipment may be added as the project progresses, increasing overall power demand.
Ignoring Fuel Consumption
Fuel costs can become significant on longer projects.
Our Diesel Generator Fuel Consumption Guide explains how generator size affects operating costs and runtime.
Generator Hire vs Buying
For many construction projects, generator hire services offer significant advantages.
Benefits include:
- Lower upfront costs
- Access to modern equipment
- Flexible generator sizing
- Maintenance support
- Rapid replacement if required
For long-term projects or ongoing site operations, commercial generator sales solutions may be more appropriate.
The right choice depends on project duration, budget, and operational requirements.
You can also read our guide to buy or hire a generator for a more in depth look.
How To Choose The Right Construction Site Generator
The best generator is one that:
- Meets current power requirements
- Handles startup loads safely
- Provides room for future expansion
- Operates efficiently
- Supports site safety requirements
If you're unsure what size generator your project requires, our What Size Generator Do I Need? guide provides a broader overview of generator sizing considerations.
Need Help With Construction Site Power?
SGH provides generator hire, temporary power solutions, commercial generator sales, installation services, and ongoing support for construction projects across Australia.
Whether you need power for a small residential build or a large commercial development, our team can help identify the right generator solution.
Explore our Generator Hire, Sales & Services Across Australia or contact SGH to discuss your project requirements.
FAQs
What size generator do I need for a construction site?
Most construction sites require generators between 20kVA and 100kVA, depending on the equipment being used and total power demand.
Can a 20kVA generator run a construction site?
Yes. Many small residential and light commercial projects can operate successfully using a 20kVA generator.
Do construction sites need three-phase generators?
Many sites do, particularly when operating welders, compressors, pumps, and larger commercial equipment.
Is generator hire better than buying?
For short-term projects, generator hire is often more cost-effective. Long-term operations may benefit from purchasing equipment.
How do I calculate generator size for a construction site?
Start by identifying all equipment that will operate simultaneously, calculate total power demand, and allow additional capacity for startup loads and future expansion. You can also check out our generator power calculator here.
