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What size microgrid does a construction site need?
That is a question that comes up very quickly once people start looking at microgrids for construction sites.
It sounds as if there should be a quick answer. A neat little table, perhaps. Ten cabins equals this size. Twenty cabins equals that size. Add a tower crane and move one column to the right.
But construction site power does not work that neatly because two sites of the same physical size can behave completely differently. One might have a handful of cabins, basic lighting and predictable daytime usage. Another might have welfare units, drying rooms, EV charging, security systems, communications equipment, pumps, heaters and a site team that quite reasonably expects everything to work without anyone needing to babysit the power system.
The size of the site matters, of course, but it is not the best starting point.
The better question is: what is the site actually using, when is it using it, and how will that change?
That is your load profile. And if you want to size a construction site microgrid properly, the load profile is where the conversation needs to start.
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Why site size is not enough
It is easy to assume a bigger construction site automatically needs a bigger microgrid. Sometimes that will be true. But the relationship between site size and power demand is not always straightforward.
A large site with a relatively simple temporary compound may have lower power demand than a smaller urban project with heavy welfare use, electric heating, drying rooms, lighting restrictions and EV charging. A housing development, road project, rail compound and city-centre commercial site may all be “construction sites”, but from a power perspective they can be completely different beasts.
That is why sizing based on square metres, number of plots or a rough description of the job can lead to problems. The system may end up too small, which creates performance issues, or too large, which increases cost and reduces efficiency.
Neither is ideal.
A good microgrid specification looks at the actual behaviour of the site, not just the size of the fence around it.
Start with the load profile
A load profile shows how much power the site uses over time. It helps answer the questions that really matter when sizing a microgrid. Read our blog – Off-grid power vs microgrids
What is the highest demand the site is likely to hit? What does the site use on an ordinary working day? What keeps running overnight? Which loads are essential? Which ones are only needed at certain times? Are there big spikes caused by heating, tools, EV charging or drying rooms? Does demand change between summer and winter?
This is where the conversation becomes much more useful than simply asking what generator is currently on site.
Measure if possible
If a site is already operating, temporary load monitoring can provide a far more accurate picture than relying on assumptions or generator nameplates. Even a few weeks of load data can reveal demand peaks, overnight consumption and generator utilisation that would otherwise be missed. This information can help identify oversized generators, unnecessary runtime and opportunities to optimise battery storage and energy management before a system is specified.
Where real-world data is available, it will almost always lead to a more accurate microgrid design than estimates alone.
A generator may have been sized for a worst-case scenario. That does not mean the site needs that level of power all day. In fact, most sites do not. They have peaks, dips and long stretches where demand is far lower than the generator capacity.
A microgrid can take advantage of that variation. Battery storage can support lower loads. The generator can step in when demand is higher or the batteries need charging. HEMS can help manage the timing of certain loads, so the system is not constantly fighting avoidable waste.
The more accurately the load profile is understood, the better the system can be specified.
Peak demand is only one part of the answer
Peak demand matters because the system has to cope when everything that needs power is running. If the site has a short but heavy spike in demand, the microgrid needs to be designed with that in mind.
But peak demand is not the whole story.
A site might only hit its maximum power demand for a short period each day. If the whole system is sized around that moment alone, it may be larger than it needs to be for the rest of the time. That can make the system more expensive and less efficient.
Average demand matters too. So does overnight demand. So does the length of time the battery needs to support the site without the generator running.
A good specification will look at the difference between the site’s highest demand, its normal working demand and its low-load periods. That gives a much clearer picture of what the microgrid needs to do.
It is a bit like planning catering for a site team. You need to know the maximum number of people who might arrive, but you also need to know whether they are all eating at once, whether half of them are only there on Tuesdays, and who keeps using the kettle like it is a competitive sport.
Welfare cabins, offices and drying rooms
Temporary accommodation is often one of the biggest drivers of site power demand, especially once heating and drying rooms are involved.
Welfare cabins and offices may not look dramatic from an energy point of view, but the loads add up quickly. Lighting, heating, kettles, microwaves, laptops, routers, printers, chargers and hot water all create demand. Then add drying rooms, which can be particularly energy hungry, and the overnight profile can change completely.
A drying room drawing around 4kW and running from 6pm to 6am results in 12 hours of continuous power consumption. On many sites, it does not need to run for that long; it is simply left on because nobody has a better way to manage it. With HEMS, that drying room load can be timed so it runs for the period required, rather than through the whole night.
That kind of detail matters when sizing a microgrid.
If the site has several loads that can be scheduled or controlled, the system may perform very differently from a site where everything is left running continuously. The equipment is important, but the behaviour around the equipment matters just as much.
Lighting, security and communications loads
Not every important load is large.
Some of the smaller loads are the ones that make site teams nervous about turning generators off. Security systems, CCTV, communications equipment, routers, alarms and essential lighting may not draw the same power as heavy tools or heating, but they often need to stay live.
A microgrid can be very useful here because battery storage can support those lower overnight loads silently, without keeping a generator running just to power a relatively small amount of equipment.
Lighting also deserves a closer look. Perimeter lighting is often needed during hours of darkness, but not during daylight. The brochure’s HEMS example shows how a daylight sensor can control one of the outlets, switching lights off when they are not needed and back on as the sun sets.
That is the kind of thing that changes the sizing conversation.
If lighting runs all day and all night, the system has to support unnecessary consumption. If it is controlled properly, demand comes down. Over a long project, that makes a real difference.
EV charging and growing electrical demand
EV charging is becoming a more common part of construction site power planning.
It may begin with one or two chargers for site vehicles or management teams, then grow as more electric vehicles arrive. On some projects, it may be a tender requirement, a sustainability commitment or simply a practical necessity.
Either way, EV charging can change the site load profile quickly.
The important question is not just “Will there be EV charging?” but “When will vehicles charge, how many will charge at once, and does charging need to be prioritised against other site loads?”
If everyone plugs in at the end of the day, the evening demand could look very different from the daytime profile. If charging can be scheduled or staggered, the microgrid may be able to support it more efficiently.
This is where intelligent load management becomes useful. A site may not need to charge everything at full power immediately. It may need a system that can make sensible decisions about timing and priority.
Cranes, pumps and higher-demand equipment
Some site loads move the conversation into a different category altogether.
Tower cranes, pumps, batching equipment and other heavy loads can create higher power requirements that may not be suitable for a smaller system on its own. These loads can also introduce large transient demands and motor starting currents that need to be considered during system design. A site that starts with cabins and welfare may later add equipment that changes the entire power strategy.
That does not automatically mean the only answer is to jump straight to the largest possible setup from day one. It does mean the system needs to be planned with enough flexibility for what is coming next.
If a project has known future phases, those should be discussed early. The power system might need to scale. It might need multiple units. It might need a different generator arrangement. It might need a phased approach so the temporary power setup grows with the project rather than being redesigned every time demand changes.
Nobody wants to solve the same power problem three times because the first conversation was too narrow.
Quiet hours and overnight operation
Quiet hours can be one of the biggest reasons for choosing a battery-based microgrid.
On some sites, generators cannot run overnight because of local restrictions, planning conditions or residential neighbours. On others, they technically can run, but everyone would rather they did not. Noise carries, and nobody enjoys the gentle bedtime hum of a generator outside their window. Funny, that.
If the generator needs to stay off during quiet hours, the microgrid must be sized to carry the required overnight loads from the battery. This means battery sizing is often driven by required hours of autonomy rather than peak power demand alone.
HEMS can help here by making sure the batteries are charged before quiet hours begin and by controlling overnight loads more carefully. That might involve switching off non-critical loads, timing drying rooms, managing lighting and preventing unnecessary generator starts.
For sizing, this is crucial. A site that needs two hours of silent running has a very different requirement from a site that needs to run through the entire night without generator support.
Why generator size alone can mislead you
Many microgrid conversations begin with the existing generator size. That is useful information, but it should not be treated as the final answer.
A site might be using a 100kVA generator because that is what was available, what was specified years ago, or what felt safe at the time. It may not reflect the actual demand. It may be oversized. It may be running inefficiently. Or it may be needed only for occasional peaks.
If you size a microgrid only by matching the existing generator, you may miss the opportunity to improve the setup.
The better approach is to look at what the generator is actually doing. How often does it run? What load does it usually carry? When does demand peak? How much fuel is being used? What happens overnight? Which loads could be controlled?
That tells you whether the site needs more generation, more storage, better load management or a different operating strategy.
Battery capacity changes the conversation
In a generator-only setup, the generator has to be available whenever power is needed. In a microgrid, battery capacity gives the system breathing space.
The battery can support lower loads, absorb energy when the generator or renewables are available, and supply power silently when the generator is off. The question is how much stored energy the site needs.
That depends on the load profile.
A site with low overnight demand may need enough battery capacity to run essential loads until morning. A site with drying rooms, heating and security loads may need more. A site with strict quiet-hour restrictions may need the battery to carry a defined period without fail.
Battery capacity is not just about how large the system looks on paper. It is about how long it needs to support real site loads in real operating conditions.
When one microgrid unit may be enough
For many site compounds, one well-specified microgrid unit may be enough to support typical temporary loads, especially where the system is designed around cabins, welfare, lighting, communications and controlled overnight demand.
This is where EasyGrid’s plug-and-play approach is useful. The unit can be pre-configured around the site’s expected power demand, generator setup and control requirements, reducing the amount of on-site complexity.
But the phrase “well-specified” is doing a lot of work there.
One unit is only enough if the loads, running patterns and quiet-hour requirements suit the system. If the site has heavy equipment, multiple zones, expanding compounds or future phases with higher demand, the better answer may be to scale.
When you need a scalable microgrid
A scalable microgrid becomes important when the site is likely to grow, when loads are spread across multiple areas, or when demand sits between standard system sizes.
The EasyGrid messaging supports systems from 45kVA to 200kVA and beyond, with parallelised systems for larger or more flexible power requirements. The brochure also describes multiple EasyGrid units working via an on-site distribution board to deliver power to separate areas while communicating properly with generator stop signals.
In practical terms, that means the site does not necessarily need to commit to one oversized system from the start. It may be better to use a more flexible arrangement that can grow with the job.
For rental companies, this matters as much as it does for contractors. Flexible assets are easier to place across different projects. A unit that can work alone on one site and form part of a larger setup on another is far more useful than equipment that only suits one narrow application.
What information should you gather before asking for a quote?
You do not need to arrive with a perfect technical pack before speaking to a specialist. But the more useful information you can provide, the better the recommendation will be.
The most helpful starting points are the current or expected generator size, typical running hours, fuel use, peak demand, average demand, overnight loads, site operating hours and any known quiet-time restrictions. It is also useful to list the main loads: welfare cabins, offices, drying rooms, lighting, security systems, communications equipment, EV charging, pumps, cranes or other high-demand equipment.
Future plans matter too. If more cabins are arriving in three months, if EV charging is likely to be added, or if the project will move from one phase to another, say so early. A good microgrid should be designed around where the site is going, not just where it is today.
How Energy Solutions sizes EasyGrid
Energy Solutions starts with the load profile and use case rather than a generic site-size rule.
That means understanding what the site needs to power, how demand changes, what the existing generator setup looks like, whether renewables are available, what quiet-hour requirements apply and how the project may scale.
From there, the team can recommend an appropriate EasyGrid model or configuration, pre-configured to suit the site’s needs. Once deployed, the system can be monitored and adjusted so performance is not left to guesswork.
That is important because construction sites are not static. Loads change. People plug new things in. Working hours shift. Weather changes the demand for heating or cooling. Site teams discover new and imaginative ways to use power.
A system that can be monitored and optimised is much more useful than one that is simply dropped on site and left to fend for itself.
The right size is the one that fits the site behaviour
Choosing the right microgrid size is not about finding the biggest system you can justify. It is about matching the system to the way the site actually uses power.
Too small, and the site may struggle during high-demand periods or quiet hours. Too large, and you may pay for capacity that rarely gets used. Poorly controlled, and even the right hardware can underperform.
The best results come from understanding the load profile, planning for future changes and using battery storage, generator control, renewables and HEMS in a way that suits the project.
So if you are asking what size microgrid your construction site needs, the honest answer is: it depends on the load, not just the site.
And that is a good thing, because it means the system can be designed around the job you are actually doing.
Talk to an Energy Solutions Power Specialist to review your site load profile and find the right EasyGrid configuration for your project.
Energy Solutions designs, builds and supports intelligent energy systems for land, sea and off-grid environments. From EasyGrid hybrid microgrid systems to commercial battery storage, bespoke engineering, distribution and remote monitoring, our team helps organisations reduce generator runtime, improve energy visibility and deploy reliable power infrastructure that works in the real world.
To discuss your off-grid, temporary, hybrid or commercial energy storage requirements, speak to an Energy Solutions Power Specialist.