About this report
This report is a simulation study of smart charging of electric cars at home, carried out at Ghent University within the InterFlex project. It asks how much of the value of smart charging depends on the habits of the people who use it. It is written for a broad audience of stakeholders across the energy ecosystem.
How this report was made
This report was made with the help of generative AI: large language models, including Claude by Anthropic, used as coding agents in the Cursor editor. Under the author’s direction, these agents wrote the code of the simulation model and of the analysis, ran and checked the analyses, drew the figures, and drafted this report and its website version. The author, an energy economist with more than ten years of research experience on residential flexibility and electricity markets, set the research question, made the modelling choices, interpreted the results, and reviewed and steered both the model and the writing through many rounds of detailed feedback.
The results rest on the assumptions set out in Chapter 2, Chapter 5 and the appendix, and are meant as input for discussion rather than as a forecast. Readers who spot an error are warmly invited to let the author know, so that it can be corrected.
Executive summary
Smart charging software can cut the cost of charging an electric car at home. But software can only work with the room the household gives it. This report asks how much of the value of smart charging depends on two everyday habits: plugging the car in when you get home, and letting the software decide how full the battery needs to be.
The headline results cover 2,539 simulated Flemish households, each followed for a full year, quarter-hour by quarter-hour, using measured household consumption, solar production and 2024 electricity prices, and the Flemish capacity tariff. Each household was simulated with uncontrolled (“dumb”) and smart charging, and with two simple bundles of habits: “bad” and “good”.
Dumb charging
bad habits
€727
Smart charging
bad habits
€603
Smart charging
good habits
€368
Average annual cost of charging the car at home, over 2,539 simulated Flemish households.
- Technology alone captures about a third of the prize. Moving from dumb to smart charging while keeping bad habits lowers the average annual EV bill from €727 to €603: a saving of €125 (17.1%).
- The two habits are worth more than the technology itself. Adding them lowers the bill by a further €234, to €368. Together the two steps save €359, about half (49.4%) of the bill. The behaviour step is the larger of the two for 70% of households.
- Of the two habits, letting the software choose the charge level matters most (€131 on its own, against €93 for plugging in more often), and the two reinforce each other.
- The two steps earn money in different ways. The technology step is almost entirely a capacity-tariff saving (€120 of €125): smart charging spreads the refill so that monthly peaks are lower. The behaviour step also unlocks solar self-consumption and cheap hours, so it is worth most to households with solar panels (up to €300 with 12 kWp) and a dynamic contract (€306, against €166 on a fixed one).
- Hardware matters for the technology step, not for behaviour. With a slow 2.5 kW charger, smart charging with bad habits saves nothing; the behaviour step still saves about €201 there.
- Good habits also benefit the grid massively. Charged dumb with bad habits, the car raises the household’s average monthly peak from 4.5 to 8.8 kW. Smart charging alone brings that down to 6.5 kW; with good habits as well, the car adds only 0.15 kW to the household’s peak.
- The result is robust. Across the sensitivity checks the full prize stays between €346 and €372. For a driver who never lets the battery drop below half, the two steps are about equal, because such a high personal minimum acts as a leftover bad habit.
What this means. Promoting smart charging technology on its own leaves about half of its potential benefits on the table, for households and for the grid. Products and policies should also help people plug in routinely and trust the software with the charge level, and the price signals that make those habits pay (the capacity tariff and dynamic contracts) carry much of the value. Chapter 7 sets out the recommendations.
1The question: why would habits still matter?
Smart charging is usually presented as a technology story. Install a smart charger, and software shifts charging to cheaper or sunnier hours and away from the evening peak, fully automatically. Nobody has to press a button.
Yet the software can only act within the room the household gives it, and two habits decide how much room that is. Plugging in: the software can only charge when the car is connected, so a car standing unplugged in the driveway cannot use the cheap hours of the night or the sunny hours at noon. The charge target: many drivers ask for a full battery every morning. That forces the software to fill the battery whatever the coming days look like, even when waiting a day for sun or low prices would cost the driver nothing in comfort.
Hypothesis
Most of the potential value of smart charging remains unrealised without the right behaviours.
To test this, we compare two deliberately simple bundles of habits (Figure 1). With bad behaviour, the car is plugged in only when the battery runs low, on about a quarter of arrivals home. That is a realistic picture of today: in data measured by charge-point operators, Elia finds that only 15–35% of Belgian electric cars are connected to a charger at any given moment1. Whenever the car is plugged in, it must be full by the next morning. With good behaviour, the car is plugged in on most evenings and there is no morning target: the software charges what the coming trips need, plus a safety margin, and more only when that is cheap.
Bad behaviour
Plugging in
Only when the battery drops below 20%
in practice about 24% of arrivals home
Charge target
100% full by the next morning
Good behaviour
Plugging in
On 80% of arrivals home, so most evenings
in practice about 83% of arrivals home
Charge target
None: the software decides how full the battery must be
A note on words
“Dumb” and “smart” charging are the everyday terms, and we use them throughout. They are not neutral: in the academic literature the same two regimes are more often called uncontrolled and managed (or controlled) charging. Likewise, “bad” and “good” behaviour are shorthand for two deliberately simple extremes, chosen to make the comparison easy to follow. They are not moral judgements (“bad” only means bad for the bill), and real households sit somewhere in between.
2How the study works
2.1 Four combinations, two steps
Crossing the two charging regimes with the two bundles of habits gives four combinations, and each household is simulated in all four (Figure 2). The comparison is made in two steps. The technology step moves from dumb to smart charging while keeping bad habits. The behaviour step then adds the good habits, on top of smart charging. This order mirrors how households adopt: they buy the charger first and change their habits later, so the behaviour step measures what is still left on the table once the technology is in place.
2.2 What smart charging means here
Whenever the car is plugged in, the smart-charging software plans ahead for up to 14 days. It knows the household’s own electricity use, the solar production, when the car will next leave and return, and, on a dynamic contract, the hourly prices. It then decides, for every quarter-hour the car is connected, how much to charge, so that the household’s electricity bill is as low as possible (Figure 3). It always leaves enough charge for the next trip plus the driver’s safety margin, and under bad behaviour it must also reach 100% by morning.
The software is given perfect foresight. Real products have to forecast and will capture somewhat less, so the technology step should be read as an upper bound for what software can do. The behaviour step is about giving the software room, so its logic does not depend on that assumption, although the exact euro amounts do.
What the software sees
14 days ahead, with perfect foresight
- 1The rest of the household’s electricity use
- 2Solar-panel production
- 3When the car will next be home and plugged in, and for how long
- 4Electricity prices, if the household has a dynamic contract
What it decides
For every quarter-hour the car is plugged in: whether to charge, and how much.
Goal: the lowest household electricity bill, while always leaving enough charge for the next trip plus the driver’s safety margin.
How it saves money
one optimisation, three ways to win
Raise solar self-consumption
Charge when the panels produce more than the house uses, instead of exporting that energy for very little.
Lower the capacity tariff
Spread charging so that it adds as little as possible to the household’s monthly peak.
Buy grid energy cheaply
On a dynamic contract, charge in the hours when electricity is cheap.
Why?What is the capacity tariff, and why does it matter so much here?
Since 2023, Flemish households pay part of their grid costs according to their peak: the highest quarter-hour of electricity use in each month, averaged over the year2. In this study each kilowatt of that average monthly peak costs about €53 a year, VAT included. Charging a car at full power in the evening, on top of cooking and heating, easily adds several kilowatts. Without an electric car, the simulated households have an average monthly peak of 4.5 kW.
That is why the capacity tariff turns out to be the largest single source of savings in this study: about 61% of the full prize (Section 3.1). Under a different tariff design that share would be different.
2.3 Thousands of different households
There is no such thing as “the” Flemish EV household. Battery size, charger power, kilometres driven, solar panels, the contract and the rest of the house’s consumption all change how much smart charging and good habits are worth. We therefore built 4,000 synthetic households from six building blocks (Figure 4). The first is a measured 2024 quarter-hour consumption profile of a Flemish home without solar panels or an electric car, from Fluvius3 (with or without a heat pump). The others are drawn independently, with every allowed value equally likely. Each household is then simulated for a full year, quarter-hour by quarter-hour.
The headline results use the 2,539 households whose driver has a range-anxiety threshold of 20% and, under bad behaviour, a morning target of 100%. The other households, with a 50% threshold or an 80% target, are used for the sensitivity checks in Chapter 4.
Real Fluvius consumption
2024 · quarter-hourly
no PV / no EV
Driving lifestyle
annual km, WFH
Contract
dynamic / fixed
Solar PV
0 – 12 kWp
Charger
2.5 / 5 / 10 kW
Battery
40 – 120 kWh
= one fully configured household, simulated for a full year under each combination of charging and behaviour
2.4 The yardstick: the annual EV electricity bill
Every euro figure in this report is an annual EV electricity bill: the household’s total electricity bill with the electric car, minus what the same household would have paid without it. The bill without the car is simulated too, with the same house, solar panels and tariffs. The EV bill therefore captures not only the energy bought for the car, but also its effect on the capacity tariff, on the per-kWh grid fees and taxes, and on how much of the household’s own solar production is used at home rather than exported.
A simplifying assumption
All charging happens at home. Drivers who charge largely at work or at public fast chargers are not modelled. As a rule of thumb, a household that does only half of its charging at home should halve the euro savings in this report. The one exception is an emergency: when the battery would run empty on the road, the car charges at a public charger, and that cost is kept out of the home bill.
3What we found
3.1 The headline: technology is only half the prize
Figure 5 fills the four boxes of Figure 2 with money. Start at the top left: with dumb charging and bad habits, charging the car at home costs an average household €727 a year. Switching to smart charging while keeping the habits brings this down to €603, a saving of €125 (17.1%). Adding the two good habits brings it down to €368: a further €234. The behaviour step is worth almost twice the technology step, and together they halve the bill (−€359, −49.4%).
Why?Why does smart charging save so little when habits are bad?
With bad habits the car is plugged in rarely, nearly empty, and must be full by morning. The software has almost no choice about when or how much to charge; all it can do is spread the refill over the night instead of charging at full power on arrival. That flattens the monthly peak: the average monthly peak falls from 8.8 to 6.5 kW. That is almost the entire technology step: €120 of the €125 is capacity tariff (Figure 6). Solar energy and cheap hours stay largely out of reach: among households with solar panels, the share of their own solar production used at home does not rise at all (25.0% before, 24.1% after).
Why?Why does plugging in more often raise the bill with dumb charging, to €763?
Mostly bookkeeping. With good habits the battery is kept full, so the car almost never runs low on the road. Energy that bad-habit drivers buy at public chargers (69 kWh a year, which is not part of the home bill) is now bought at home (8 kWh public), and the battery also ends the year fuller. Only about €7 of the difference comes from higher peaks. Counting public charging, the two dumb boxes cost almost the same (€762 and €767). The lesson stands either way: without smart charging, good habits buy nothing.
Leaving public charging out of the home bill makes the results conservative rather than flattering. Bad habits push more charging to expensive public chargers (69–81 kWh a year) than good habits do (21 kWh). Counting that energy at €0.50 per kWh, the technology step becomes €119, the behaviour step €264 and the full prize €383.
Figure 6 shows where the euros come from. The technology step is a capacity-tariff story. The behaviour step saves on the capacity tariff too, cutting the average monthly peak further, to 4.7 kW, almost back to the 4.5 kW of the same households without a car. But it also saves €86 on the energy bought from the grid, because more of the household’s own solar energy goes into the car (self-consumption rises from 24.1% to 33.8%) and, on a dynamic contract, more charging happens in cheap hours. Every kWh that is not taken from the grid also avoids the per-kWh grid fee and excise duty, worth another €48.
Averages hide a wide spread (Figure 7). For the middle 80% of households the full prize lies between €129 and €647 a year, and almost every household gains. The technology step is lopsided: the typical household saves only €38, 31.5% of households pay slightly more after it, and a tail of households with fast chargers saves several hundred euros. The behaviour step is broad and almost always positive (median €216; only 1.7% of households pay more after it); it is larger than the technology step for 70% of households.
Why?How can a step make some households pay more?
It sounds contradictory: smart charging minimises the bill, and good habits give it more room. Yet some households pay more after a step, for two different reasons.
After the technology step (31.5% of households). All of them have a slow charger (2.5 or 5 kW), and the amounts are small: a median of €23 a year, and less than €50 for 84% of them. With bad habits, a car is sometimes plugged in only shortly before it leaves again. It cannot reach 100% in that time anyway, so the morning target falls away and smart charging charges only what the next trip needs. That is the cheapest choice for that night, but the car leaves with less in the battery. It runs low sooner, which forces extra plug-ins later, at moments the driver did not choose (on average 46 a year becomes 65), and less of the household’s own solar energy ends up in the car (1,362 becomes 1,230 kWh a year). Dumb charging avoids this by accident, because it fills the battery whenever it can. With a slow charger there is no peak saving large enough to make up for it (Section 3.6). The optimiser does its job for each session; across the year, without the habit of plugging in, the sessions it gets are not good ones.
After the behaviour step (42 households, 1.7%). They are almost all heavy drivers (about 24,000 km a year, against 14,343 on average) with a small battery (48 kWh on average), most without solar panels (30 of 42) and on a fixed contract (37 of 42). With bad habits, their battery so often runs nearly empty on the road that they charge about 667 kWh a year at public chargers, which is paid outside the home bill. Good habits keep the battery fuller and bring most of that charging home (667 becomes 206 kWh). The home bill rises, but the household’s total charging cost falls: counting public charging, only 4 of the 42 still pay more.
3.2 Which habit matters most?
Figure 8 opens up the behaviour step, starting from smart charging with bad habits (€603). Plugging in on most evenings, but still demanding a full battery every morning, saves €93. Dropping the morning target, while still plugging in only when the battery runs low, saves more: €131. Both together save €234, which is €10 more than the two separately.
Why?Why is giving up the morning target worth more than plugging in more often?
Every session with a 100% target ends in a forced fill, whatever the price, the sun or the actual need. Extra plug-in windows under such a target are mostly extra forced fills, so they help less than one might expect. Without a target, even a car that is plugged in rarely can skip an expensive night and charge only what the next trips require. The two habits reinforce each other because extra windows become valuable only when the software may choose which of them to use. For product design this matters: the charge target is a default setting that an app controls, whereas the habit of plugging in has to be built.
3.3 Which households gain most?
Figure 9 compares the average saving between two groups of households that differ in one characteristic, for each step separately. The answer depends on which prize you look at. For the technology step, charger power dominates: from −€12 at 2.5 kW to €326 at 10 kW. For the behaviour step, battery size, solar panels and the contract take the top three places, and charger power matters little. For both steps together, charger power, contract and solar matter most, followed by how much the household drives.
Why?Why do bigger batteries gain less from the technology step but more from good habits?
With bad habits, a car is plugged in when its battery is down to about 20% and must be full by the next morning. For a 40 kWh battery that refill fits comfortably into a night at low power, so smart charging can flatten the peak. For a 120 kWh battery the refill is three times larger and needs the charger near full power for most of the night, so there is little left to flatten. Under smart charging with bad habits, the car’s capacity-tariff cost therefore rises from €44 with the smallest battery to €162 with the largest, while under dumb charging it is about the same for every size. Good habits remove the constraint: frequent top-ups replace one big refill, and a big battery then gives the software more room to store cheap or solar energy.
3.4 Contract: dynamic prices make good habits pay
On both contracts the technology step saves about the same (€115 on a fixed contract, €134 on a dynamic one). The behaviour step almost doubles on a dynamic contract: €306 against €166 (Figure 10).
Why?Why does the contract matter for the behaviour step but hardly for the technology step?
The technology step is mostly a capacity-tariff saving, and the capacity tariff is the same on both contracts. A dynamic price changes hour by hour. To profit from it, the car has to be connected when prices are low and the software has to be free to fill it up then, rather than at whatever time a morning target dictates. Those are exactly the two good habits. The difference is not a side effect of other household traits: among households driving 10,000–20,000 km a year, the behaviour step is €183 on a fixed contract and €324 on a dynamic one.
3.5 Solar panels: good habits turn them into a good match
The technology step is worth about the same with or without solar panels (€129–€132). The behaviour step grows steadily with the size of the installation, from €150 without panels to €300 with 12 kWp, and the share of the household’s own solar production used at home rises with it (Figure 11).
Why?Why does solar not help the technology step?
With bad habits the car is seldom plugged in during sunny hours, and when it is, it is often in a hurry to reach 100% by morning. The software cannot move much charging under the solar curve, so self-consumption hardly moves in the technology step (39% → 38% with 3 kWp). Good habits change that: the car is connected more often and is free to wait for the sun.
The self-consumption percentage itself falls as the installation grows because it is a share of the solar production: a 12 kWp roof produces far more than one car can absorb, even though the car then uses more solar energy in absolute terms and saves more euros.
3.6 Charger power: why the bills differ, and why they converge
Charger power is the hardware lever of the technology step. With a 2.5 kW charger, smart charging with bad habits saves nothing; with 5 kW it saves €65; with 10 kW it saves €326 (Figure 12). The behaviour step, by contrast, is large at every charger power (€201–€253). The bills at the start differ widely (€546, €677, €963), yet after both steps they end up close together (€357, €360, €389).
Why?Why are the starting bills so different, from €546 to €963?
Almost entirely because of the capacity tariff. With dumb charging and bad habits, the car arrives home nearly empty in the early evening and charges at full power, on top of the household’s own evening use. Nearly every month contains such an evening, so the monthly peak becomes roughly the household’s evening use plus the charger’s full power. A faster charger therefore means a higher peak, and every kilowatt of average monthly peak costs about €53 a year:
| 2.5 kW | 5 kW | 10 kW | |
|---|---|---|---|
| Average monthly peak, dumb + bad | 6.0 kW | 7.9 kW | 12.6 kW |
| EV capacity-tariff cost, dumb + bad | €76 | €183 | €430 |
| Rest of the EV bill, dumb + bad | €470 | €494 | €534 |
| EV capacity-tariff cost, smart + good | €3 | €7 | €13 |
| Households with at least one full-power fallback session a year | 86% | 55% | 25% |
The rest of the bill differs much less. It is a little higher for fast chargers because a fast charge finishes entirely in the expensive evening hours (on a dynamic contract), whereas a slow one runs into the cheaper night and, in afternoon sessions, soaks up more solar energy. The difference is not caused by other household traits: households with a 10 kW charger pay about €400 more than comparable households with a 2.5 kW charger.
Why?Why does a fast charger leave so much more for smart charging to save?
Because it buys time. A slow charger needs most of the night just to deliver the energy the car must have by morning, so there is nothing left to optimise. A fast charger can deliver the same energy in a fraction of that time, so the software can hold back during the household’s own evening peak, wait for cheaper or sunnier hours, and still fill the battery before departure.
Why?Why are the final bills close, but not identical (€357 / €360 / €389)?
With smart charging and good habits the software throttles every charger to what the household needs, so the capacity-tariff cost of the car almost disappears (€3, €7 and €13). What remains has three causes. First, the three groups are different households, and the gap between €357 and €360 is within the statistical margin; after correcting for differences in driving and equipment, the faster chargers end up €11 and €24 more expensive than 2.5 kW. Second, now and then there is not enough time before departure to charge smartly, and the software falls back to charging at full power. That happens more often with slow chargers (3 times a year at 2.5 kW, against 0.3 at 10 kW), but each such session costs far more on a fast charger, because it sets a high peak for that month. Third, a small remainder in energy and taxes that we have not traced further.
Why?How can smart charging cost slightly more than dumb charging with a 2.5 kW charger?
Under bad habits, a short afternoon plug-in before an early departure leaves no time to reach 100% anyway. Dumb charging simply charges flat out, which happens to top up the battery. The smart software, seeing that the target cannot be met, charges only what the next trip needs. That is sensible for the session, but the car leaves with less charge and has to plug in more often later. With a slow charger there is hardly any capacity-tariff saving to offset this, so for 64% of 2.5 kW households the technology step on its own costs a little money.
3.7 Driving and working from home
Households that drive more save more euros: €298 a year below 10,000 km, €420 above 20,000 km. But they save a smaller share of a much larger bill (64% against 36%), and keep a far larger bill after both steps (€747 against €170). Which household “benefits most” depends on whether you count euros or percentages (Figure 13).
Why?Why do heavy drivers save more euros but a smaller share?
A heavy driver needs most of the energy that the charger can deliver while the car is at home, so there is less slack to move charging around. A light driver’s small need can be placed almost entirely in the cheapest or sunniest hours. But the heavy driver shifts more kilowatt-hours in absolute terms, so the euro saving is still larger.
Working from home shows the same pattern (Figure 14). Households working from home two days a week save a larger share of their bill than those who never do (56% against 41%), but slightly fewer euros. In this model a day worked from home is a day without driving, so working from home mostly acts through fewer kilometres. The car is at home more often, but it also needs less energy, so it does not measurably soak up more of the household’s own solar production.
4How robust are the results?
Three assumptions could plausibly change the picture, so each was varied (Figure 15). A more anxious driver, who plugs in whenever the battery drops below 50% instead of 20%. A softer morning target of 80% instead of 100% under bad behaviour. And, with that 80% target, a target that is only a minimum (“at least 80%”) instead of an exact level.
The full prize holds up: it stays between €346 and €372 in every case. The behaviour step stays large (€163–€234), and so does the technology step (€125–€183). One thing does move. For the anxious driver the technology step (€183) is slightly larger than the behaviour step (€163), the only case in which the two swap order, and the bill after both steps is €418 instead of €368.
Why?Why is the bill after both steps €418 for a driver with a 50% anxiety threshold, and not about €368?
Because a high anxiety threshold is a piece of bad behaviour that survives inside “good” behaviour. The threshold is not only the level at which the driver plugs in. The software also has to respect it: every time the car leaves, it must have enough charge for the trip plus the threshold. Dropping the morning target therefore never frees the battery completely. At 20% that floor is low, but at 50% it works like a softer version of the rigid morning target that defines bad behaviour.
The effects follow directly. The battery is kept much fuller (on average 46% of capacity at a 20% threshold, 63% at 50%; at its lowest point in the year, 7% against 27%). The part of the battery that the software may empty and refill whenever it is cheapest shrinks from roughly 80% to 50% of the battery. And sessions in which there is not enough time to reach the higher level before departure become more frequent (1.4 against 6.2 a year); those fall back to charging at full power, which raises monthly peaks. After correcting for other differences between the two groups of households, the 50% threshold adds about €44 a year to the bill, of which €15 is capacity tariff and most of the rest energy bought at less favourable moments.
The practical lesson sharpens the behaviour message: letting the software decide how full to charge also means not holding on to a high personal minimum.
Why?Why does the same anxious driver gain more from the technology step?
Under bad habits the anxiety threshold is also what triggers plugging in. At 50% the car is plugged in more often and almost never runs into an emergency on the road (14 against 1.4 emergencies a year). More, earlier plug-ins give smart charging more room to spread the charging, which lowers the capacity-tariff cost. That is why the technology step is larger here (€183 against €125) and the behaviour step smaller, while the total barely moves.
The two target checks barely move the final bill, because the good bundle has no morning target at all: changing the target only changes the starting point. An 80% target makes bad behaviour a little less bad (€741 instead of €727 at the start), and the bill after both steps stays at €369. Allowing the battery to go above 80% when that is cheap (a floor rather than an exact level) changes almost nothing (€369 in both cases).
5Limitations
The model is detailed, but it is a model. These are the simplifications that matter most for reading the results.
- A sweep, not a survey. Every household characteristic was drawn with all allowed values equally likely: half of the households have a dynamic contract, a fifth have 12 kWp of solar panels and a third have a 10 kW charger. That is far from Flemish reality, so the averages in this report are averages over the range of possible households, not over the actual population (Chapter 6 proposes how to fix this).
- Perfect foresight. The software knows the next 14 days exactly. Real products forecast, so the technology step is an upper bound.
- Simplified driving. On weekdays the car only commutes, and on days worked from home it does not move; weekend outings are added on top. Consumption is a fixed 0.18 kWh per km, without seasonal variation or holidays.
- Solar production comes from the national production profile, which is smoother and probably more generous than the output of a single roof.
- One year. Household consumption, solar production and prices are those of 2024, and each household is simulated once per combination. Bill averages are stable at this sample size; counts of rare events are less precise.
- Belgian tariff design. About 61% of the full prize comes through the capacity tariff. Under a purely per-kWh grid tariff, that part would largely disappear.
- Home charging only, and no home battery or vehicle-to-grid. Both extensions could change how much the habits matter.
6Future work
6.1 A population that looks like Flanders
The most important next step is to make the averages empirically grounded. The simulation deliberately covers the full range of possible households, but the real Flemish population is not spread evenly over that range. Dynamic contracts are still a minority, most solar installations are smaller than 12 kWp, home chargers come in standard ratings (about 3.7, 7.4 and 11 kW), and characteristics come in combinations: large solar installations, higher consumption and fast chargers tend to go together in detached houses, and large batteries go with high mileage.
This does not require new simulations. Simulating broadly keeps rare but important groups well covered; each simulated household is then weighted by how common its combination of characteristics is in reality (post-stratification, standard survey practice). Two points need care. The reference population is households that drive an electric car and can charge it at home, which are more likely than the average household to have solar panels, a dynamic contract, a heat pump and a larger car. And the data will be patchy: sources such as VNR (contracts), Fluvius (solar installations and grid connections) and Statbel or FEBIAC (the vehicle fleet) cover some characteristics well and others not at all; where the evidence runs out, the assumption should be stated rather than hidden. The result would be the first estimate of what the two steps are worth for a typical Flemish home-charging household.
6.2 Scenarios for 2030 and 2035
The same weighting can be applied to a future year. A scenario fixes explicit assumptions about how common each characteristic will be, for example the share of dynamic contracts, solar panels and their size, charger power, battery size and heat pumps, and reports the average technology and behaviour steps in that year. Because the households are already simulated, each scenario is only a different set of weights. The table below shows what a scenario would have to specify, and the direction in which Chapter 3 suggests each change would push the results. The scenario values themselves would have to be sourced and agreed.
| What a scenario fixes | In this study | Plausible direction by 2030–2035 | Expected effect (from Chapter 3) |
|---|---|---|---|
| Share of dynamic contracts | half of households | rising | behaviour step larger |
| Solar panels: how many households, how large | 0–12 kWp, evenly spread | more and larger installations | behaviour step larger |
| Home charger power | 2.5 / 5 / 10 kW, evenly spread | shift towards 7.4 and 11 kW | technology step larger; dumb charging more expensive |
| Battery size | 40–120 kWh, evenly spread | larger batteries on average | technology step smaller, behaviour step larger |
| Heat pumps | about half of households | rising | behaviour step slightly smaller |
Holding prices, tariffs and consumption profiles at their 2024 values keeps such scenarios cheap. Projecting those as well (future price patterns, a different capacity tariff) would need new simulations and is a second, larger step.
6.3 Further extensions
- Imperfect forecasts: rerun smart charging with a shorter or imperfect look-ahead, to see how much of the technology step a real product would keep.
- Richer driving data: base trips on the Flemish travel survey (OVG)4, including weekday errands and holidays.
- Realistic rooftop solar profiles, and other price years than 2024.
- Home batteries and vehicle-to-grid: with a car that can also feed energy back, plugging in may matter even more.
- Observed plug-in behaviour: compare the simulated habits with measured plug-in rates and session lengths.
7Takeaways and recommendations
Smart charging pays, but the technology on its own captures only about a third of what is possible. Good habits pay as much again, and more, but only if charging is smart (Figure 16).
Dumb charging
Bad behaviour
€727
baseline
step→
Smart charging
Bad behaviour
€603
−€125 vs baseline
step→
Smart charging
+ good behaviour
€368
−€234 vs smart + bad
−€359 vs baseline
The two habits:
- Plug in whenever you get home
- Let the software choose how full to charge
Households
- Plug the car in whenever you get home, even when the battery is not low.
- Let the software decide how full to charge: ask for “enough for my trips” rather than “100% every morning”, and keep any personal minimum modest.
- Expect the largest gains with a dynamic contract and solar panels. With a slow charger, the habits are what make smart charging pay at all.
Industry: charger makers, carmakers, suppliers, aggregators
- Hardware and algorithms are necessary but not sufficient. Design products that build the habit of plugging in.
- Make “charge what I need” the default instead of a fixed morning target, and earn the trust that makes users accept it, for example with a guaranteed minimum range and a visible charging plan.
- Where users can set a minimum charge level, default it low and show what a higher level costs.
Policy: governments, regulators, grid operators
- Promoting the adoption of smart charging technology on its own leaves about half of the potential benefits on the table, not only for households but also for the grid. Support for smart charging should also target plugging-in and target-setting habits, and programmes are best judged by the flexibility that is actually available, not only by the number of devices installed.
- Households gain most where the capacity tariff bites, and more still on a dynamic contract. These price signals carry much of the value of good habits, so changes to tariff design will change what smart charging and good habits are worth.
ATechnical appendix
Extended list of assumptions that went into the simulation work performed for this report.
| Simulation | One year (2024) at quarter-hour resolution. 4,000 households, each simulated under every combination of charging regime and behaviour, once per combination. Headline results: the 2,539 households with a 20% anxiety threshold and a 100% morning target (run 2026-09-09_174504). |
|---|---|
| Household consumption | Measured 2024 quarter-hour profiles from Fluvius3, of homes without solar panels or an electric car, with or without a heat pump; drawn with replacement. |
| Solar production | Elia’s national production profile for 20245, scaled to 0, 3, 6, 9 or 12 kWp. |
| Prices | Belgian day-ahead prices for 2024 (Ember)6. Dynamic contract: 1.5 c€/kWh plus 1.05 × the wholesale price for electricity taken from the grid; 0.98 × wholesale minus 2 c€/kWh for exported solar energy (which can be negative). Fixed contract: one flat price per kWh, derived from 2024 wholesale prices weighted by the consumption profiles of comparable Fluvius households, plus a 5% supplier margin. |
| Grid fees and taxes | Capacity tariff €50 per kW per year on the average monthly peak; per-kWh grid fee €0.05; excise €0.05 per kWh; VAT 6%. |
| Car and charger | Battery 40, 60, 80, 100 or 120 kWh; charger 2.5, 5 or 10 kW; 0.18 kWh per km; charging losses not modelled; battery half full at the start of the year. |
| Driving | Weekday commutes (one-way distance drawn per household), no driving on days worked from home (0–3 a week), weekend outings. Annual distance: median 12,949 km; middle 80% 6,693–24,466 km. |
| Behaviour | Bad: plug in only when a trip leaves the battery below the anxiety threshold (20%), and reach 100% by the morning. Good: plug in on 80% of arrivals home (plus any plug-in forced by the threshold), no morning target. In both, a public charger is used (at €0.50/kWh, outside the home bill) if the battery would otherwise run empty on the road. |
| Dumb charging | Full charger power from the moment the car is plugged in, until the battery is full. |
| Smart charging | A linear optimisation that plans up to 14 days ahead with perfect foresight and minimises the household’s bill: energy, the increase in the capacity tariff, per-kWh fees and taxes, with solar energy valued at its export price. Each departure must leave with the next trip’s energy plus the anxiety threshold. If no feasible plan exists, the horizon is shortened; if that also fails, the session is charged at full power. |
| Drawn characteristics | Number of households in the headline results: Battery (kWh): 40 (540), 60 (477), 80 (487), 100 (518), 120 (517); Charger (kW): 2.5 (833), 5 (879), 10 (827); Solar PV (kWp): 0 (548), 3 (473), 6 (521), 9 (511), 12 (486); Contract: fixed (1,298), dynamic (1,241); Work-from-home days / week: 0 (413), 1 (1,288), 2 (445), 3 (393); Heat pump: no (1,248), yes (1,291). |
| Annual EV electricity bill | The household’s total electricity bill with the car minus the bill of the same household without it, both simulated. Technology step = dumb + bad minus smart + bad; behaviour step = smart + bad minus smart + good; full prize = both. |
References
- Elia (2025). Adequacy and flexibility study for Belgium 2026–2036 (AdeqFlex’25), June 2025. Box 3-6, pp. 108–109: share of electric cars connected to a charger, measured by three charge-point operators (about 25,000–30,000 charge points), January 2023 – October 2024.
- Vlaamse Nutsregulator (VNR, formerly VREG). Capacity tariff for electricity distribution in Flanders, in force since 1 January 2023.
- Fluvius. Quarter-hourly electricity consumption profiles of a sample of Flemish households with a digital meter, calendar year 2024.
- Flemish Government, Department of Mobility and Public Works. Onderzoek Verplaatsingsgedrag Vlaanderen 7 (OVG 7), 2023–2024.
- Elia Open Data. Photovoltaic power production on the Belgian grid (dataset ods032), calendar year 2024.
- Ember. European wholesale electricity price data: Belgian day-ahead prices, calendar year 2024.