What if your construction site connection comes too late?

Apply as soon as the permit is in, ask for a size the grid can deliver quickly, and bridge the gap with power you control. For many business sites that means a temporary connection below 25 kVA, or a generator, together with a battery that delivers the peaks. The battery is built like a fixed business battery: cells, a battery management system, an inverter and a controller. How to size one for a site is in our article on the site battery (werfbatterij). This article is about the connection itself: how long it takes, why, and what to do while you wait.

The shell construction starts in six weeks. The tower crane is booked, the site huts arrive on Monday, and the planning assumed power from day one. Then the grid operator answers: for the power you asked, a study comes first. Or you hear nothing, and the only date you get is "we will plan it".

What nobody puts in the site budget is the time in between. A site that waits for power runs on diesel. A generator sized for the crane burns fuel all day, even when only the kettle in the site hut is on. Add refuelling, noise for the neighbours, and an inspection of the site cabinet that must be done before the connection. A few weeks of delay become a cost that is on no quote.

Running a site without the grid is possible, and we do it on permanent sites. In Zele, Special Renting Van Zele runs its warehouse, offices and electric lifting gear without any grid connection, because the grid study offered none. It uses 30 kWp of solar panels, a battery, and a generator for about 5% of the yearly need. On a farm in St-Georges-sur-Meuse the street had no connection, so the farm ran on a generator day and night. With solar panels and a battery (30 kVA, 46.2 kWh), the generator is now only the back-up.

How long does a construction site connection take in Belgium?

In Flanders, a temporary site connection below 25 kVA can be live within about five weeks. From 25 kVA, the maximum terms add up to about six months. Those are the terms in the Flemish technical regulation for distribution (TRDE), if you answer at once and nothing is extended.

A temporary connection is one for a building site or an event, strictly limited in time, and below 25 kVA. Fluvius tells you within five working days whether it can carry out the request, and sends an offer within five working days after that. After you approve the offer, you can demand the connection within 15 working days. VITO, which keeps the Flemish guide to best available techniques, says the same: a temporary connection can be arranged within five weeks.

From 25 kVA it is a connection with a prior study. The grid operator checks your file within ten working days. It then sends an offer or a reasoned refusal within 30 working days (40 from 1 MVA). After you approve the offer and pay any advance, you can demand the works within 18 weeks, for connections up to 5 MVA.

In Wallonia, the regulator CWaPE sets the terms for the offer. The grid operator (ORES or RESA) sends it within 10 working days of a complete file for a simple case. When the grid must be extended, it has 30 working days. Once all conditions are met, the meter is put into service within 3 working days. ORES limits a site connection to two years, longer if the works are delayed, and delivers the power "subject to the availability of the grid". In Brussels, Sibelga works with an offer request that includes photos of the site.

Why does 25 kVA decide how long you wait for a site connection?

Because at 25 kVA the Flemish rules switch from the quick procedure to a study. A temporary connection is by definition below 25 kVA. Above it, the grid operator first checks what the local grid can take.

On a 3 x 400 V connection, 25 kVA is about 36 A per phase. Site huts, lighting and hand tools fit well under it. A tower crane or a builder's hoist pushes a site over it fast. That is why Fluvius asks on its application form for the power of the crane, and whether it has a soft start (a controller that lets the motor start gently). A crane that starts hard needs more from the grid than its running power suggests.

The study also costs money. In Flanders the study fee in 2026 is 246.94 euro excluding VAT between 25 and 56 kVA, and 493.90 euro up to 1,000 kVA. You pay it even if you do not accept the offer. Between 25 and 250 kVA the grid operator also decides where you connect: on the low-voltage grid, directly on a transformer station, or on the medium-voltage grid. From 250 kVA it is always medium or high voltage.

So the real question is not how much power the site needs, but how much of it must come from the grid. If a battery delivers the peaks of the crane, the grid only has to deliver the average. Our article on the site battery works this out for a site with a small 25 A connection and a crane.

How do you apply for a construction site connection with Fluvius, ORES or Sibelga?

You apply online with your grid operator, or through your energy supplier: Fluvius in Flanders, ORES or RESA in Wallonia, Sibelga in Brussels. Fluvius handles the request in Mijn Fluvius, ORES through an online form.

Fluvius offers three set-ups. A temporary connection with a temporary cable is only possible where there is an overhead grid or a street cabinet. A temporary connection with the definitive cable uses the cable that will later feed the building. Or you ask for the definitive connection right away and use it as the site connection. The definitive cable saves you a second visit and a second trench.

Have this ready before you apply:

The weak point is often on your own side. Book the inspection of the site cabinet before the connection date, not after. If the inspector comes after the grid operator, the cable is there and the site still has no power.

What are your options while you wait for the site connection?

You have five realistic options, and only one of them is to wait. They differ in when the power is there, what it can carry and what it costs you every day.

VITO lists a site connection as a best available technique for building sites for one reason: it avoids diesel generators. Electric machines are quieter, and there are no exhaust gases, noise or vibrations from generators. VITO also warns that not every site qualifies, because high peaks such as electric cranes can exceed what the grid can deliver.

A battery changes the job of the generator. It no longer runs all day to be ready for the crane. It charges the battery in short runs at a good load, and a controller starts and stops it automatically. How the two work together is in our article on a generator with a battery.

Can a small site connection with a battery replace a heavier one?

Often yes, for the construction phase. The battery charges from the small connection when the site is quiet, and adds its power when the crane lifts. The grid then only has to deliver the average, not the peak.

That can be the difference between a temporary connection within weeks and a study that takes months. The sizing comes down to two numbers: the peak in kW, which sets the inverter, and the energy per working day in kWh, which sets the battery. The site battery article shows the calculation step by step, so we do not repeat it here.

The technology is the same as in our fixed business battery systems: a battery, an inverter and a controller. The inverter can also run as an island (on its own, without the grid). The controller decides when to charge and when to deliver. On a site without any connection, the charging comes from a generator or solar panels instead.

Can you claim compensation when the grid operator connects your site too late?

Yes, but it will not pay for a site that stands still. In Flanders the Energy Decree sets a flat amount for every day the grid operator exceeds the term. It is 50 euro per day for a temporary or simple connection that is not for a home, and 100 euro per day for a connection with a detailed study. For a home it is 25 euro.

The grid operator does not pay if it proves it could not prevent the delay. And the term only runs when your side is in order: the grid operator may deviate from the agreed date when the applicant does not keep the agreements. Fluvius explains how to claim on its compensation page.

In Wallonia, the CWaPE lists a flat amount per day beyond the connection date planned in the offer: 25 euro for a household, 50 to 100 euro for a non-residential customer.

Compare that with a crane crew that cannot lift. The compensation is a reason to get the dates in writing, not a plan B.

What if the final connection of the building is the real bottleneck?

Then the site connection is only the first delay. Fluvius replaces the site connection with the definitive one once the building is wind- and watertight. A warehouse or workshop that needs far more than the site did goes through the study route for that final connection. In a congested area it can then be flexible, late or refused.

Check it before the works start. The Fluvius capacity map (Capaciteitswijzer) gives, per parcel and for several power levels, an indication of the expected lead time, the cost and the distance to the medium-voltage grid. In Wallonia, ORES warns that designing, permitting and building new grid capacity sometimes takes several years. For the permanent connection of a business in Wallonia, read how a business connection with ORES or RESA works.

Did the grid study already say no to the final connection? Then our article on a new building without a grid connection shows how a building can start on its own power and connect later. Was a heavier connection refused or postponed? Read your options when a heavier grid connection is refused. And if the offer asks for your own cabin, compare a medium voltage cabin with a battery first.

What happens when you ask us to bridge the wait on your site?

We start with what must run on site and when, not with a device.

1. Step 1: Analysis and sizing. We list the crane, hoist, site huts, drying and tools, and work out the peak in kW and the energy per day in kWh.
2. Step 2: Technical design. We choose the battery, the inverter power and the charging source: the small connection, a generator, solar panels or a mix.
3. Step 3: Installation and commissioning.
4. Step 4: Monitoring and support. You follow the system remotely and see when the battery needs charging.