kW vs kWh: the difference on your Belgian bill

A kW measures power; a kWh measures a quantity of energy. The distinction sounds like a physics lesson, and in Belgium it still was one five years ago. Since Flanders began billing part of the network on peak power, it is worth several hundred euros a year — and it does not read the same way depending on your region.

What is the difference between a kW and a kWh?

The kilowatt (kW) is a rate: what your installation draws from the grid at a precise moment. The kilowatt-hour (kWh) is a volume: what you actually took off the grid over a period of time. FEBEG, the Belgian federation of electricity and gas companies, sums the relationship up in one line: 1 kWh is the energy consumed by a 1,000-watt appliance running for one hour.

The tap analogy works well here, as long as you do not stop halfway. The kW is the width of the jet — how much water comes out per second when you open it. The kWh is the volume in the bucket at the end. Two households can fill the same bucket: one opened the tap fully for ten minutes, the other let it trickle all morning.

Until recently, in Belgium, only the bucket counted. That is changing.

The maths fits on one line: power × time = energy

Power in kW × duration in hours = energy in kWh.

A 2 kW portable heater running for 3 hours uses 6 kWh. A 2.2 kW kettle running for 3 minutes uses only 0.11 kWh, even though its power rating is almost identical: duration does all the work. And if you want to go the other way, divide energy by time — 6 kWh spread over 3 hours is an average power of 2 kW.

Above all, remember this: you do not convert kW into kWh. You multiply them by a time. That is why an online "kW → kWh" converter cannot produce anything meaningful unless you also give it a duration.

What your appliances use, and what it actually costs

Here is the translation into euros at the all-in Belgian price recorded in August 2026 — roughly €0.30/kWh including the 6 % residential VAT, network costs and taxes. The power ratings are orders of magnitude for common household equipment, not manufacturer specifications.

Two rows deserve a pause. The kettle has almost the same power rating as the oven and costs twenty-five times less to run: the fear of "power-hungry appliances" often aims at the wrong target, because it looks at the kW while the bill looks at the kWh. The charging point, by contrast, combines both — high power and long duration. It is the one item that reshapes a household's bill, and we put numbers on it in our guide to the best electricity supplier for an electric car.

In Flanders, the kW has become a bill line of its own

This is the point almost no English-language article explains to people living in Belgium, because most of them are written for other markets.

Since 2023, Flemish households with a digital meter pay a capacity tariff (capaciteitstarief): part of the network costs is no longer billed per kWh drawn, but per kW of peak power. The meter records the average power drawn in each fifteen-minute block; the highest block of the month becomes your monthly peak, and the bill is based on the average of your last twelve peaks. In other words, running the tumble dryer, the induction hob and the car charger at the same moment costs more than running them one after the other — for exactly the same number of kWh.

The amounts are not symbolic. In 2026 the price sits between €52 and €60 per kW of peak per year depending on the network operator, with a floor peak of 2.5 kW billed to everyone, meaning €130 to €150 a year even for a very frugal household. Fluvius, the Flemish DSO (distribution system operator), puts the average monthly peak of a Flemish household at 4.24 kW.

Let us run the calculation nobody publishes. At a 4.24 kW average peak, the capacity tariff comes to €220 to €254 a year. Set against an annual electricity bill of €1,304 to €1,589 for a 3,500 kWh profile in August 2026, that means roughly 14 to 20 % of a Flemish household's bill is charged per kW, not per kWh. A fifth of the bill no longer depends on how much you consume, but on how you consume it.

The spread between profiles is of the same order. An average peak of 4 kW costs €208 to €240 a year; a peak of 6.5 kW, €338 to €390. Between the two, about €130 to €150 a year, for the same quantity of energy. Suppliers pass the tariff on unchanged — Engie details it in its customer area, while Mega, Luminus and Eneco show it on the "distribution costs" line of your statement. The Flemish regulator, VREG, publishes the official grid per network operator.

Wallonia, Brussels, Flanders: where do you pay per kW and where per kWh?

The answer changes by region, which is precisely why a foreign article, or a "Belgian" article that does not separate the three, will mislead you.

In Wallonia, CWaPE — the Walloon energy regulator — confirmed two changes on 1 January 2026: new dual-hour time bands (off-peak from 10 p.m. to 7 a.m. and from 11 a.m. to 5 p.m., seven days a week) and the launch of the Impact tariff, an optional distribution tariff for holders of a communicating meter who can shift large loads, typically electric-vehicle drivers. It is not a general capacity tariff, and it remains optional. In Brussels, Brugel has not generalised power-based billing for households either.

Regional tariff grids change every year: check yours on your annual statement rather than trusting an article, this one included.

Does it matter if you live in Wallonia or Brussels?

Less than in Flanders, but not nothing — and for a reason that has nothing to do with the bill.

The objection is fair: if your bill is calculated entirely per kWh, spreading your usage across the day earns you nothing directly. A Brussels household that runs the tumble dryer while the oven is on will pay exactly what it would have paid two hours apart. There, the priority remains volume: fewer kWh, and a better price per kWh.

Three qualifications still temper that conclusion.

• Your connection capacity is a physical limit. Stacking an EV charger, a water heater and an induction hob can trip an ordinary domestic installation, whatever the region. That is a safety matter, not a pricing one, and it is handled by a certified electrician — never by working on the fuse board yourself.
• The Walloon dual-hour tariff already rewards timing. Since January 2026 the 11 a.m.–5 p.m. window is billed at the off-peak rate: moving the washing machine to the afternoon pays, even without a capacity tariff.
• Moving house changes the rule. Someone leaving Wallonia for Flanders inherits the capacity tariff along with the digital meter, often without seeing it coming in that first annual statement.

In short: in Wallonia and Brussels, watch the kWh and the price per kWh. In Flanders, watch both.

kVA, watt, amp: the other units people confuse with the kWh

kW versus kWh is only the most visible confusion. Four others come up constantly, and three of them trip up readers who rely on non-Belgian sources.

• The watt (W) is simply a kW divided by a thousand. A 1,500 W appliance is a 1.5 kW appliance; a 60 W appliance running for an hour uses 0.06 kWh. Product sheets mix the two notations freely.
• The kVA measures apparent power, the kW active power. On an ordinary domestic installation the two are close. The real trap lies elsewhere: in Belgium you do not subscribe to a kVA level the way French households do with EDF. Your connection capacity is set by your DSO — ORES, Fluvius, RESA or Sibelga depending on your municipality — and does not appear as a contract option with your supplier.
• The amp (A) describes the current your circuit breaker can carry. On single-phase 230 V, a 40 A breaker tolerates roughly 9.2 kW; on three-phase 400 V, the same current supports considerably more. That is why an 11 kW charging point is unremarkable on a three-phase installation and impossible on some single-phase ones.
• The MWh equals 1,000 kWh. You will not meet it on a household bill, but you will in the reports of the CREG, the federal energy regulator, and in regulatory thresholds — the 50,000 kWh line separating a residential from a professional customer, for instance.

These distinctions are not vocabulary pedantry. They decide what you can plug in, what you pay, and what a salesperson can tell you without your being able to check it.

Once the units are clear, only one figure needs comparing from one supplier to the next: the price per kWh, standing charge included. Our ranking of the best electricity suppliers sets them side by side by consumption profile, and our bill simulator turns your annual kWh into euros. If your last bill came as a shock, start instead with our guide to an electricity adjustment bill that is too high: nine times out of ten the problem is neither the kW nor the kWh, but the monthly instalment.