Belgium's saturated electricity grid: the myth of all-electricity revealed

The myth of "all-electric" versus the reality of the Belgian grid

For several years now, the message has been hammered home by public authorities, the media and those involved in the energy transition: photovoltaic panels (PV) + heat pump (PAC) + electric vehicle (EV) = successful transition. On paper, the equation looks coherent: we electrify our homes and supply them with decentralised renewable energy.

In real life, this equation becomes fragile - even dangerous - as soon as we introduce two realities that nobody wants to face:

• 📊 Networks have physical limits (maximum current, voltage variations, transformers, cables sized for another use)
• ❄️ "Newly electrified" uses (heating, mobility) consume especially when PV produces the least: winter evenings, cold snaps, short, grey days, etc.

In December 2025, ORES, Wallonia's main distribution network operator (GRD), sounded the alarm in an explosive internal document presented at its general meeting. The punch line that should be at the centre of the public debate:

"The model of 'everything, everywhere, all the time and right away' is no longer sustainable today." - ORES, December 2025

ORES identifies 4 simultaneous revolutions that are piling up on the same ageing infrastructures:

1. Decentralised production of renewable energy (massive residential PV)
2. Decarbonisation of heating (electric heat pumps)
3. Electric mobility (vehicles and fast-charging stations)
4. Electrification of industry (industrial processes, data centres)

So it's not a question of "liking electricity" or "hating oil/gas". The problem is believing that we can electrify on a massive scale without demand management, storage, flexibility and back-up solutions.

The alarming figures from ORES: a network at the end of its tether

The official data published by ORES in December 2025 paint a stark picture of the critical state of the Walloon electricity network:

At the same time, connection requests are exploding at an unsustainable rate:

What the grid can (and can no longer) guarantee: physical limits

Two fundamental constraints: temperature and voltage

ORES points out that any electricity network has to deal with two types of inescapable physical constraints:

For years, the focus has been on overvoltage (PV injecting too much locally, inverters stalling in summer). Today, undervoltage is once again a major issue... because the demand for power is exploding with the electrification of heating and mobility.

The low-voltage network has not been designed for this scenario

ORES explicitly describes that at feeder level (neighbourhood low-voltage supply), there are now simultaneously:

• ☀️ Surges linked to residential photovoltaic installations (massive localised injection on sunny days).
• ⚡ Undervoltages linked to excessive withdrawals: fast-charging terminals and home heat pumps, etc.

And the figure is huge: 10,000 circuits out of 70,000 are deemed vulnerable to this double constraint. Historically, low-voltage networks were designed for unidirectional extraction (power station → house), not for managing bidirectional injection + tenfold consumption peaks.

"Low-voltage networks were originally designed for withdrawal. Electricity is now available locally and intermittently. Balancing the network has an increasing cost." - CWaPE, presentation December 2025

Undervoltage: the new invisible threat of "all-electricity".

In an article published on 10 December 2025, Le Soir reveals a largely underestimated emerging problem: undervoltages on the Walloon grid. Unlike overvoltages (caused by excess photovoltaic production in summer), undervoltages result from simultaneous excessive consumption - exactly the scenario that the massive electrification of heating is causing.

The critical scenario described by ORES

ORES sets out a very concrete situation in black and white in its December 2025 presentation:

"If on the way home from work everyone recharges their cars, makes food, turns on the heat pump, is there a risk of encountering a voltage problem? Yes. The voltage could drop to 200V, a level at which the heat pump won't start." - ORES, internal presentation December 2025

When thousands of heat pumps start up simultaneously in cold weather (returning from work 5pm-8pm), combined with charging electric vehicles in the evening and preparing dinner, the grid voltage can drop below 207V. At this critical level:

• 🚫 Heat pumps refuse to start (built-in thermal protection).
• ⚠️ Sensitive electronic devices malfunction (computers, modern household appliances)
• 📉 The quality of the electricity supplied deteriorates dangerously (risk of damage to equipment)
• 🔌 Photovoltaic inverters may also stall (abnormal voltage detected)

👉 This is a key point: a customer equipped solely with a heat pump for heating becomes dependent not only on the price of electricity and the availability of the grid, but also on local voltage quality - a parameter they have absolutely no control over and which deteriorates precisely at the times when they need it most.

High voltage: power is becoming scarce (and sometimes denied)

The statement "high voltage is already saturated everywhere" is not an exaggeration. ORES provides a very telling snapshot of the situation at Elia transformer stations (high-voltage transmission network):

To put it plainly: 27 substations are already refusing, 58 will refuse within 5 years without any major changes, and only 35 out of 122 substations (29%) look like they could hold out in the medium term. The very notion of "guaranteed connection" is becoming obsolete.

ORES explicitly states that current contracts guarantee "all the power requested regardless of the time or season", but this permanent band is no longer, in many cases, a realistic/adapted solution.

2026 tariffs in Wallonia: an admission of impotence disguised as "modernisation

Faced with this critical situation, the CWaPE (Walloon energy regulator) unveiled a major tariff reform in December 2025, applicable from 2026. The official objective, formulated in administrative language, is "to match production and consumption in order to reduce constraints on the network and control the cost of investment in infrastructure".

In pragmatic terms, this means that the grid can no longer guarantee constant power to everyone, all the time. Consumers are now being encouraged - or forced - to shift their usage to times when the network is under less strain.

A revealing legal framework

The Walloon tariff decree, explicitly cited by the CWaPE, sets out two principles that seem contradictory but reveal the reality:

"Consumers who do not wish to contribute flexibility to the energy system must not be financially penalised by the new tariff structure... [but] each tariff component provides an incentive for network users who wish to do so to consume at a time when there is an abundance of electricity on the network." - Article 4, §2, paragraph 2, 27 of the Walloon tariff decree

In other words: we're not officially forcing you... but if you don't change your habits, you'll pay significantly more.

New tariffs for 2026

Impact tariff and dynamic prices: for whom?

The CWaPE is very direct about the profile required for flexible tariffs. Consumers must:

• ✅ Have the technical capacity (or the time) to start up high-consumption appliances at times when prices are low
• ✅ Avoid starting these high-consumption appliances at the most expensive times of day
• ✅ Follow the price curves communicated the day before for the following day
• ✅ Plan your day-to-day consumption accordingly

PV + heat pump: a logical combo... but highly seasonal (and that changes everything)

Let's be honest and balanced: PV + heat pump can be excellent for most of the year. In mid-season (March-April, September-October), the combination works remarkably well:

• 🌤️ Efficient heat pump: moderate temperatures = high COP (3.5 to 4.5)
• ☀️ Sun present: long days, decent amount of sunshine
• ⚡ Usable PV production: directly supplies the heat pump during the day
• 💰 Real savings: high self-consumption, reduced bill

So the "PV + heat pump = perfect combo" argument is not totally false. It's just incomplete. Because the critical moment for the Belgian/Walloon grid is precisely when this beautiful mechanism breaks down:

• ❄️ When it's cold (maximum heating requirement)
• 🌑 When it's dark (short days 8am-4pm)
• ☁️ When the sky is overcast (grey weeks in November-January)
• 🏠 When everyone goes home (peak 5pm-9pm)
• 📉 When the heat pump is most in use (continuous operation in very cold weather)

Winter time mismatch: the system's Achilles heel

This is not an ideological judgement against PV or the heat pump. It's an inescapable physical fact:

1. Heating demand is correlated with cold (direct proportionality)
2. Sunshine is minimal in winter (8h of daylight, 4-5h of which can be used)
3. Peak demand occurs in the late afternoon/evening (after sunset)
4. The heat pump's COP falls with temperature (COP 2-2.5 at -5°C vs. 4-5 at +7°C).

And it is precisely in this scenario that "all electric uncontrolled" becomes a risky strategy if you have no storage, no control and no back-up.

Removing a functional heating system (gas/oil): sometimes counter-productive

Amid all the excitement about the "hunt for fossil fuels", one practice is becoming widespread and is even encouraged by certain regional grants: dismantling a perfectly functional oil or gas boiler to install an all-electric heat pump. This approach, however well-intentioned, poses several major problems.

The illusion of energy savings in real conditions

A customer switching from an oil (90% efficiency) or gas (95% efficiency) boiler to a heat pump (average annual COP 3.5-4) will indeed make substantial savings... on average over the year. But what about during the critical winter period?

These extra 625-1000 kWh of electricity are added to the demand on the grid at the worst times (cold snaps, evenings without sunshine, consumption peaks). And if the grid fails? No heating at all. No ability to cook. No comfort at all.

Resilience sacrificed on the altar of dogmatic electrification

A hybrid heating system (heat pump + fossil-fired boiler as back-up/booster) offers incomparable robustness:

• ✅ Economic optimisation: the heat pump works when it's cost-effective (high COP, cheap electricity, available network)
• ✅ Security of supply: the boiler takes over in the event of a grid failure, undervoltage, extreme cold spell or prohibitive tariffs
• ✅ Grid relief: during critical peaks, the heating system automatically switches to fossil fuel, immediately freeing up electrical capacity for other users
• ✅ Longer service life: both systems operate less intensively, reducing wear and tear and breakdowns
• ✅ S ystem coherence: we are responding to ORES, which explicitly states that "everything right now" is no longer sustainable

"Keeping a boiler running as a back-up is not an ecological betrayal, it's energy life insurance. The real waste is throwing away operational equipment that still has 10-15 years of potential life in order to install another that is totally dependent on a faulty electricity network. Pragmatic ecology is one that works every day, in all weathers, without jeopardising the comfort and safety of residents." - Wattuneed philosophy

Pragmatic solutions: flexibility, storage, hybridisation

Faced with the impasse of "uncontrolled all-electricity", three strategic axes emerge from the official documents of ORES and CWaPE:

1. Flexibility: definition and applications

ORES defines flexibility as "the ability to modify one's energy injection or withdrawal profile in response to a signal, in order to provide a service to the electricity system and/or to obtain a financial advantage".

There are three levels of flexibility:

2. Energy storage: the key to autonomy and resilience

Installing a storage battery radically changes the game and transforms a vulnerable PV+PAC installation into a robust system:

• 📦 Maximised self-consumption: PV energy produced during the day is stored for use at night and in the morning
• ⚡ Peak shaving: the battery supplies the heat pump and appliances in the evening (5pm-10pm), avoiding straining the grid at critical times
• 🔋 Emergency back-up: in the event of a power cut or local undervoltage, the battery maintains essential equipment (critical circuits or the whole house, depending on size)
• 💰 Intelligent tariff arbitration: charge at off-peak times (low tariff), discharge at peak times (high tariff) → substantial savings with Impact/dynamic tariff
• 🌍 Network service: possibility of participating in commercial flexibility mechanisms (remuneration by the DSO).

Battery sizing according to use

3. The hybrid inverter: the intelligent energy conductor

Thehybrid inverter is the brain of your modern solar installation. Unlike a conventional PV inverter (which simply feeds solar energy into the grid or supplies power to the house), the hybrid inverter intelligently manages three simultaneous flows:

1. Photovoltaic generation: DC → AC conversion + multi-string MPPT optimisation
2. Battery storage: charge/discharge according to programmed strategy (self-consumption, off-peak hours, tariff arbitration)
3. Electricity grid: bi-directional withdrawal/injection according to instantaneous needs and current tariffs

The advanced modes of modern inverters (Sofar ESI, Deye, WKS EVO) allow in particular:

• 🌙 Of f-peak mode: battery charging on the grid when electricity is cheap (11pm-7am), discharging at peak times
• 🏠 Se lf-consumption mode: maximises local use of PV energy, minimises grid injection
• 🚨 Backup / EPS mode: automatically switches to battery power in the event of a mains failure or detected undervoltage
• ⚖️ Dynamic arbitrage mode: financially optimises charging/discharging according to Impact/dynamic tariffs (with integrated weather forecast)
• 🔌 Zero injection mode: prevents any grid injection (saturated areas, unfavourable prosumer tariff)

4. Vehicle-to-Grid (V2G): your EV becomes a giant battery

An emerging but promising technology could revolutionise domestic energy flexibility: Vehicle-to-Grid (V2G). How does it work? Use the colossal battery of your electric vehicle as a storage system for your home.

Why V2G is a radical game-changer

• 🔋 Colossal capacity: a 60 kWh EV battery = 12 times a 5 kWh domestic battery
• 🏠 Powering the home in the evening: the EV returns the accumulated electricity to power the heat pump, appliances and lighting
• 💰 Massive tariff arbitrage: charging at off-peak times (or on PV during the day if teleworking), discharging at peak times
• ⚡ Paid network services: participation in the DSO's commercial flexibility mechanisms (additional income)
• 🌍 Grid relief: avoids simultaneous consumption peaks in the evening

Concrete example of V2G usage:

Find out more about this technology: 🔗 EV & V2G batteries: full guide

Grid investment: billions needed... but when?

ORES has presented an investment plan structured around 3 major axes to modernise and strengthen the Walloon network :

The major problem? These massive investments will take years to materialise (studies, authorisations, worksites), require colossal budgets that will inevitably be reflected in electricity bills, and do absolutely nothing to prevent the current saturation point.

The article in L'Avenir on 10 December 2025 confirms this unambiguously: "ORES's investment plan needs to be revised upwards, which could mean a further increase in electricity bills".

To put it plainly: the network will not be up to standard before 2030-2035 at the earliest, at a time when massive electrification (CAP, EVs, industry) is already here and accelerating. The period 2025-2032 will be critical, with growing tensions between explosive demand and limited supply. Individual solutions (storage, flexibility, hybridisation) are not optional: they are imperative if we want to maintain comfort and energy resilience.

What can you do as an individual? The 3 possible architectures

Scenario A - "Pure electric" (heat pump + EV) without storage or back-up

Configuration: Heat pump alone for heating + EV + possibly PV without batteries

Advantages:

• ✅ Maximum theoretical decarbonation (zero direct fossil fuels)
• ✅ Maximum eligibility for regional subsidies (depending on current policy)
• ✅ Simpler installation (only one heating system)

Major disadvantages:

• ❌ Total dependence on the grid in critical periods (winter, evenings)
• ❌ Sensitivity to undervoltage: PAC that does not start at 200V (documented case ORES).
• ❌ Extreme tariff sensitivity with dynamic tariffs: impossible to move heating.
• ❌ Maximum contribution to network saturation at worst times.
• ❌ No resilience: network failure = cold house immediately.

Conclusion: Consistent only in very robust areas (Group 4 ORES substations), risky elsewhere. Not recommended by Wattuneed except in very specific cases.

Scenario B - "All electric intelligent" (heat pump + EV + control + battery)

Configuration: heat pump + EV + sized PV installation + 10-20 kWh lithium battery + hybrid inverter + home automation control system

Advantages:

• ✅ Maximised PV self-consumption (70-90% depending on sizing)
• ✅ Peak shaving: battery supplies house + heat pump in the evening
• ✅ Partial resilience: backup essential circuits or entire house (depending on inverter)
• ✅ Tariff arbitration: substantial savings with Impact/dynamic tariff
• ✅ High decarbonation maintained
• ✅ Participation in commercial flexibility possible (GRD remuneration)

Disadvantages:

• ❌ High initial investment (battery + hybrid inverter: +€5000-8000)
• ❌ Increased technical complexity (parameterisation, maintenance)
• ❌ Limited autonomy in the middle of winter: 1-2 days maximum without grid.

Conclusion: Excellent compromise if budget available and desire to remain 100% electric. Solution of the future recommended by Wattuneed for new buildings or heavy renovations.

Scenario C - "Resilient hybrid" (heat pump + back-up + control ± battery)

Configuration: main heat pump + gas/oil boiler/woodstove as back-up + possibly PV + battery + automatic switchover control.

Advantages:

• ✅ Maximum heating resilience: operates in any weather, at any mains voltage
• ✅ Grid relief during critical peaks (back-up activated automatically)
• ✅ Intelligent economic control: Heat pump when COP favourable + low tariff, back-up otherwise
• ✅ Consistent with grid reality: responds to ORES call for "all the time" to end
• ✅ Making the most of existing equipment: no wastage if boiler is working
• ✅ Easier maintenance: two independent systems = redundancy

Disadvantages:

• ❌ "Less pure" decarbonation (but often more robust systemically)
• ❌ Double maintenance: heat pump + boiler (but limited back-up use = low wear and tear)
• ❌ Potentially reduced incentives depending on regional policy

Conclusion: the most realistic and pragmatic scenario in a Wallonia where reliable access to electrical power is becoming problematic. Strongly recommended by Wattuneed for renovations where a functional boiler exists, or for areas identified as fragile (Group 1-2 ORES stations).

Wattuneed recommendations: checklist for a resilient installation

Conclusion: real ecology is the kind that works in January at 7 p.m.

If we want an energy transition that works every day, in all weathers, including during cold snaps and evening peaks, we absolutely must get away from the simplistic slogan "PV + CAP = universal solution".

ORES explicitly and unambiguously documents:

• 📉 The physical limits (maximum current, critical voltage variations)
• ⚠️ The massive vulnerability of part of the LV network (10,000 circuits out of 70,000)
• 🚫 The current saturation of 27 HV substations + 58 additional ones by 2030 without flexibility
• ❄️ The concrete scenario where the CAP may not start up under undervoltage (200V)
• 🔄 The end of the "everything, everywhere, all the time and right away" model.

The CWaPE, for its part, is clearly gearing tariff rules and regulations towards :

• ⏰ Time shifting of consumption (automatic bi-hourly, Impact, dynamic prices)
• 📱 Active adaptation by consumers (prices communicated the day before, daily monitoring, steering)
• 💰 Marked price differentiation between those who adapt and those who are left behind.

The electrification of heating and transport is an ecological necessity - no one at Wattuneed disputes this. But it must imperatively be accompanied by :

1. 💾 Massive storage to smooth peaks and guarantee autonomy
2. 🔄 Intelligent flexibility to adapt demand to available supply
3. 🌡️ Hybrid systems to guarantee real energy resilience
4. ⏰ F ine-grained time management via dynamic tariffs, home automation and controls

"Abandoning a functional fossil heating system to install an all-electric heat pump with no storage, no control and no back-up is, in the current state of the Belgian network documented by ORES and CWaPE, a high-risk decision. Saving 200 litres of heating oil in winter only to find yourself without heating in the event of network undervoltage, local saturation or a breakdown is not environmentally friendly: it's energy recklessness." - Wattuneed SPRL

At Wattuneed, we believe in a pragmatic, resilient and functional energy transition. Our solutions combine :

• ☀️ Photovoltaics sized (production = annual consumption)
• 🔋 Lithium battery storage (10-20 kWh depending on use)
• ⚡ Intelligent hybrid inverters (advanced modes, backup, arbitration)
• 🌡️ Hybrid approach when relevant (heat pump + back-up heating)
• 📱 Home automation (automatic optimisation without constraints)

Because a house without heating in the middle of winter is not environmentally friendly. Because true ecology is one that works every day, in all weathers, without jeopardising the comfort and safety of the inhabitants.

❓ Frequently asked questions (full FAQ)

Does it still make sense to install a heat pump in Belgium in 2025-2026?

Yes, but not on their own. A correctly sized heat pump, combined with a storage battery (10-15 kWh minimum), an intelligent hybrid inverter and ideally a back-up system (wood, gas, oil), is still an excellent solution. The important thing is not to be 100% dependent on the electricity grid at peak times (5pm-10pm) and during periods of potential undervoltage. ORES explicitly documents the risks of the heat pump not starting up at 200V.

How many kWh of battery do you need for a residential installation with a heat pump?

Sizing according to profile:

• Minimum viable: 10 kWh → covers night-time needs (3-4 kWh) + 3-4 hours of heat pump in the evening (5-6 kWh) + safety margin.
• Recommended optimum: 15-20 kWh → almost complete autonomy for 24 hours, excluding extreme cold, with the possibility of DSO flexibility.
• Maximum comfort: 25-30 kWh → multi-day backup, aggressive price arbitration, resale of commercial flexibility

Favour modular systems (Sofar BTS, Pylontech US5000, Delong) that can be expanded as needs change.

Are Impact tariffs and dynamic pricing compulsory in 2026?

No, but bi-hourly tariffs are. The CWaPE clearly states:

• Dual time: automatic and not optional for everyone (forced switchover)
• Impact tariff: optional, requires R3 communicating meter + movable loads + explicit request to the supplier
• Dynamic prices: optional, requires daily monitoring capacity and active management

Interesting if installation with battery + home automation (automatic optimisation). Otherwise, conventional two-hourly pricing is sufficient without major penalty (but full/expensive price differential to be anticipated).

Has my current PV installation (without battery) become obsolete?

No, but it can be improved. It is still useful for reducing bills (instantaneous self-consumption + paid injection according to contract). To maximise resilience and self-consumption (70-90%), the addition of a battery via AC Coupling is strongly recommended. Wattuneed offers retrofit solutions for adding :

• Hybrid inverter (Deye, Sofar, WKS) in parallel with the existing PV inverter
• Modular lithium battery (5-20 kWh)
• Intelligent control (off-peak modes, backup, arbitrage)

See guide: AC Coupling: 6 possible configurations

Will the Belgian grid really "crack" in the years to come?

The term "crack" is excessive, but the constraints will be very real and measurable. ORES documents this in black and white:

• 27 HV substations are already refusing any new connections (group 1)
• 58 additional substations will be saturated by 2030 without any flexibility (group 2)
• 10,000 LV circuits out of 70,000 vulnerable (overvoltage AND undervoltage)

Expected consequences 2025-2032:

• Refusal of professional connections (recharging stations, battery parks, industries)
• Localised undervoltages (residential areas with high PAC/VE density)
• Targeted power cuts possible (technical flexibility as a last resort)
• Highly differentiated tariffs (indirect non-flexibility penalty)

Network investment will take at least 10-15 years. Critical period 2025-2032 → individual resilient solutions imperative.

Is keeping my old oil/gas boiler as back-up really environmentally friendly?

Yes, as part of an overall system approach. Several angles:

1. Equipment carbon footprint: Throwing away a working boiler (10-15 years left) = manufacture + transport + installation of a new heat pump + recycling of the old one + waste. Immediate carbon impact not negligible.
2. Reduced heat pump efficiency in extreme cold: a heat pump forced to operate at -10°C with a COP of 1.5-2 consumes 500-650 Wh of electricity per kWh of heat. If electricity produced by gas/coal power stations (Belgian winter mix), indirect carbon footprint similar or worse than direct boiler.
3. Grid relief = less investment: Booster activated 10-15% of the time (cold peaks) frees up network capacity → less reinforcement → less concrete/copper/steel → favourable overall balance.
4. Resilience = less fuel poverty: cold houses with network failure = major health and social problem.

Wattuneed conclusion: Intelligent hybrid (heat pump 80-90% + back-up 10-20%) often more environmentally friendly overall than dogmatic 100% electrification in a fragile grid context.

What should I do if my neighbourhood is identified as an area prone to unplugged UPS (power surges)?

Concrete actions:

1. Check via the ORES map: Interactive map of voltage anomalies
2. Inverter configuration: Extended voltage range settings (in accordance with standards), anti-disconnection timers.
3. Zero injection mode: If chronic overvoltages, activate zero injection mode (local consumption only, surplus to battery)
4. Buffer battery: Local storage drastically reduces grid injection (surplus absorption)
5. DSO contact: Report via ORES support (network reinforcement work planned according to priority zones)

How do I know if my local HV substation is saturated or approaching saturation?

Indirect indicators:

• Industrial/commercial projects refused in your municipality (local press, town councils)
• Longer lead times for new connections (PV installers report blockages)
• Repeated incidents on the LV network (micro outages, voltage variations)

Official information: ORES does not publish a detailed public map of saturated substations (commercial confidentiality), but occasional information via :

• Pre-connection request (ORES response indicates availability)
• Regional parliamentary questions (public reports)
• Specialised local press

Does Wattuneed offer complete turnkey solutions with support?

Yes, we offer a complete package:

1. Study phase: Sizing using free tools(Toolbox) + personalised telephone advice
2. Design phase: Customisable solar kits (PV + hybrid inverter + battery + accessories) tailored to your consumption profile and heating system
3. Installation phase: Network of certified partner installers (depending on region) OR equipment delivered for installation by your electrician
4. Operation phase: Dedicated after-sales support(Helpdesk) + detailed technical guides(Expert blog)
5. Optimisation phase: Advanced settings guides (inverter modes, tariff strategies, monitoring)

📞 Need personalised advice for your project?
Wattuneed helpdesk - PV technical blog - Free toolbox

Wattuneed SPRL - Your Belgian partner for photovoltaic and renewable energy solutions since 2010. Technical expertise, personalised support, resilient solutions adapted to the Belgian grid.
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