Short answer: your electrical installation falls short the moment you want to draw more current than the old wiring and consumer unit can handle. That happens almost every time you go greener. Induction cooking, a heat pump, an EV charger and a home battery together pull so much power that an old fuse box with rewireable fuses simply cannot keep up.
The rule of thumb: if your consumer unit is more than 25 years old, still has screw-in fuses, or has no RCDs, then replacing it during an upgrade is nearly always necessary. And the moment an electrician works on your consumer unit, that part has to meet the current wiring regulations. That is not a choice, that is the standard.
What does it cost? A new consumer unit including fitting runs around 775 to 995 euros. Want to go from single-phase to three-phase, budget 300 to 500 euros for the electrician plus 600 to 1,500 euros one-off for the grid operator, these days sometimes with long waits because the network is full. A complete rewire of a whole house quickly climbs to 5,000 to 15,000 euros.
And listen, this is the point where I am strict: everything behind the meter and at the consumer unit is work for a qualified electrician. 230 volts is not something to experiment with. Below I explain exactly when your installation falls short, what you may do yourself and what you have to hand over.
Why does going greener trip up on your old wiring?
Put simply: you want to get off gas and put everything on electricity. That shifts a huge peak onto your electrical installation.
Your house used to run little on electricity. A few lights, the TV, a washing machine, maybe a ceramic hob. The old installation is built for exactly that.
Now you want to cook on induction, heat with a heat pump and charge your car. Each of those is a power hog that draws hard for hours or during peaks.
And it all comes together at one point: your meter cupboard. That is where the main connection, the consumer unit and the wiring that runs into the house sit. If that is old and built too light, then that is your bottleneck.
A feel for the numbers. A large induction hob can draw up to 11 kW at peak. A heat pump asks for 2 to 3 kW continuously in most homes. An EV charger at home does 3.7 to 11 kW. Switch those on at the same time and an ordinary single-phase connection simply gives out.
How do I know if my electrical installation is outdated?
You do not have to unscrew the meter cupboard to check this. Just look for what you recognise. Do you have:
- Screw-in or rewireable fuses in the box (those glass or porcelain things you replace). That is old kit.
- No RCD. Those wide switches with a test button. If they are not there, then your most important protection against electrocution is missing.
- Few circuits. An old box sometimes has only 3 or 4. Modern upgrades ask for a lot more.
- Fuses that trip when you switch on the kettle and the hair dryer at the same time.
- Sockets without an earth (the ones without the metal contact strips on the side), especially in older houses.
- Cloth- or rubber-sheathed wiring. Houses from before 1980 sometimes still have wiring with a cloth or fabric sheath. That is at the end of its life.
- A consumer unit more than 25 years old. Even if it still works, the standard has changed a fair bit in the meantime.
Recognise three or more of these? Then there is a good chance you cannot avoid a rewire when you upgrade.
A burning smell at the socket, flickering lights or warm switches? That is no longer a “some day” thing. That means: call an electrician now.
When does the consumer unit need replacing or upgrading?
The consumer unit is the heart of your installation. It splits the current across separate circuits and protects each circuit.
Replacing or upgrading becomes necessary the moment you need more circuits than fit, or the moment the box no longer meets the safety standard. When you go greener you nearly always run into both.
Every heavy appliance wants its own circuit. An induction hob, a heat pump, an EV charger, a home battery: each of those is a separate circuit with its own protection. In an old box with four circuits there is simply no room for that.
On top of that: the moment an electrician alters or extends your box, the altered part has to meet the current wiring regulations (BS 7671 in the UK). That means, among other things, 30 mA RCD protection on the circuits and usually a main switch. In practice an old box is then so outdated that a complete replacement is cheaper and tidier than patching it up.
In short: upgrading (extra circuits) is fine if the box is still modern and safe. Replacing is necessary if the box is old, has no RCD, or is too full.
Single-phase or three-phase: what do I need for a heat pump, induction and an EV charger?
This is the question most people get wrong. Let me make it clear.
Most older houses have a single-phase connection, often rated around 1x35A or 1x40A. That is one phase of 230 volts. Enough for an ordinary household, but tight the moment you stack heavy appliances.
A three-phase connection (often 3x25A) has three phases. You can then spread the heavy appliances across the phases, so no single phase gets overloaded. This is what you need for heavy-power appliances.
Why does single-phase so often fall short? Do the maths. On 1x35A you have roughly 35 amps at 230 volts, so about 8 kW to work with. Sounds like a lot. But:
- Induction hob: up to 11 kW at peak. This appliance alone is already over the limit.
- Heat pump: 2 to 3 kW continuously.
- EV charger: 3.7 to 11 kW.
Switch on induction and the heat pump at the same time and you are well over what single-phase delivers. The main fuse trips. That is why three-phase is the advice the moment you combine two or more of these heavy loads.
One exception: if there is only one heavy load and you behave smartly, then with load balancing you can sometimes stay on single-phase. Some heat pumps (such as those from NIBE) come with sensor coils that continuously measure your total consumption. If the rest of your house pulls a lot, the heat pump holds back for a bit. That way you stop your main fuse tripping and can sometimes stay on 3x25A. Ask your electrician whether that works for your situation.
Is my installation ready for a heat pump, EV charger or induction? The checklist
Want to know quickly where you stand? Run through this. Per heavy appliance, the minimum you need:
Ready for induction:
1. A dedicated cooker circuit in the box (often two coupled breakers, sometimes a heavy-power connection).
2. A cable of at least 2.5 mm², 4 mm² for a heavy hob.
3. Room in the consumer unit for that extra circuit.
Ready for a heat pump:
1. A dedicated circuit with the right protective device.
2. Enough connection capacity, usually three-phase, unless load balancing helps out.
3. A consumer unit that meets the current standard.
Ready for an EV charger:
1. Its own circuit, just for the charger.
2. Usually three-phase for fast charging (11 kW), single-phase does up to 3.7 kW.
3. Often a thicker cable of 4 to 6 mm², depending on power and distance.
4. An RCD of the right type (type A or B, the electrician decides that).
Cannot put a green tick against one of these points? Then it belongs on your electrician’s quote.
What is the right cable size and conductor cross-section?
Cable that is too thin for a heavy appliance is dangerous. The cable gets warm, voltage drop builds up and in the worst case the insulation melts. That is why an electrician looks at this closely.
The rule of thumb for conductor cross-section in a home:
- Ordinary lighting circuit: 1.5 mm².
- Ordinary socket circuit: 2.5 mm², up to 16 amps.
- Heavy hob or heavy power: 4 mm², to avoid voltage drop and heat.
- EV charger: often 4 to 6 mm², depending on power and the length of the cable.
An important detail many people do not know: in an ordinary home installation the earth conductor is always as thick as the live conductor. So a 2.5 mm² circuit also has a 2.5 mm² earth. Cutting corners on the earth is completely off the table.
And the length counts. A long cable to the garage or the shed calls for a thicker conductor than the same circuit right next to the box. An electrician works that out, it is not guesswork.
RCD: why 30 mA is mandatory and counts per circuit
The RCD is your life insurance in the meter cupboard. It compares the current going out with the current coming back. If current disappears (for example through your body into the ground), it switches off within a fraction of a second.
The standard: an RCD of no more than 30 mA has to switch off within 0.3 seconds. Those 30 mA are the limit that sits just below a life-threatening current through your body.
What the regulations demand for a modern installation:
- Every circuit sits behind a 30 mA RCD.
- A single two-pole RCD may cover no more than four final circuits
The three RCD limits a modern installation has to meet. .
- You may no longer put single-phase final circuits on a four-pole (three-phase) RCD. The reason: with an evenly spread load the fault signals cancel each other out and the device measures nothing. That is exactly the wrong outcome at the moment it matters.
In practice that means: with a three-phase box you get several two-pole RCDs, neatly spread. The old idea of “one big RCD for the whole box” is no longer allowed.
Does your old box have just one RCD for everything, or none at all? Then your installation is no longer safe on this point, and certainly not ready for heavy appliances.
Do the wiring regulations apply legally in a renovation?
Yes, and this is the core that many articles stay vague about, so I will make it concrete.
The wiring regulations are the standard for low-voltage installations (BS 7671 in the UK). The standard itself is not a law, but it is referenced through the building regulations. That makes it, in practice, the standard your installation has to meet.
The important distinction:
- Existing installation you do not touch: it may stay as it is, even if it does not meet the latest standard. You do not have to rebuild your whole house just because the standard has changed.
- The moment you alter or extend something: the altered part has to meet the standard that applies at that moment. New circuit? Behind a 30 mA RCD. Box adjusted? Usually a main switch added.
So: fit a heat pump, EV charger or induction and you are altering the installation, and then the current wiring regulations apply to that work. A qualified electrician knows this and hands over an installation that is right. That is why this is not a job for the handy neighbour.
Older house with no earth in the bathroom: extra caution
A headache all of its own in old houses: no earth, precisely in the spots where it is most dangerous.
In many houses from before the 1970s and 1980s the earth is missing at the sockets. In the living room that is already not great. In the bathroom or kitchen, where water and electricity come together, it is genuinely dangerous.
Without an earth your RCD has far less to work with, and a leakage current can run through your body instead of safely away through the earth. That is exactly the scenario you want to avoid.
If you are renovating, have the earthing checked straight away. An electrician checks whether there is a proper earth electrode, whether the earth resistance is right and whether all circuits are actually earthed. This is measurement work with professional equipment, not a “quick look for a green-and-yellow wire”.
Is the earth missing in wet rooms? That is a reason to rewire those circuits anyway, greener or not.
What may I do myself, and what has to be done by a qualified electrician?
Here I am strict, and I mean it. 230 volts is lethal. You cannot see a fault in the meter cupboard, but it can start a fire or cost someone their life.
What you may generally do yourself and can do safely:
- Replace a socket or a switch, provided you isolate the circuit and know what you are doing.
- Hang a light or connect a fitting.
- Check for yourself what kind of connection and box you have, so you can have a good conversation with the electrician.
What you should never do yourself, full stop:
- Work on or in the consumer unit.
- Add circuits, fit RCDs, change fuses.
- Run heavy power or a cooker circuit.
- Connect an EV charger or heat pump to the installation.
- Do anything to the main connection or the meter. There is a seal on it from the grid operator, and only an approved firm may break it.
Why so strict? Because one loose or too-thin wire in the box only starts a fire years later. Because a wrongly connected RCD does not protect you while you think it does. And because in the event of damage or fire you have no leg to stand on with the insurer if the work was not done by a qualified electrician.
Do yourself a favour. The work behind the consumer unit you hand over. That is not weakness, that is sense.
Do I need to have my main connection upgraded, and what does that cost?
Sometimes a new consumer unit is not enough and your main connection has to be heavier too. You do not arrange this yourself and neither does your electrician, the grid operator does that.
If you go from single-phase to three-phase (for example to 3x25A), the grid operator comes round. The one-off cost is roughly between 300 and 500 euros for a simple swap, but can climb to 600 to 1,500 euros if digging is needed.
Want to go heavier still, from 3x25A to 3x35A, then watch the ongoing costs. A heavier connection can raise your fixed grid charges year after year. Check the current tariffs with your grid operator, and do not go heavier than you really need.
And then the spoilsport of 2026: a full network. In some regions the network is full and the waits for an upgrade have grown to half a year or sometimes more than two years. Request this early if you have plans.
Good to know: grid charges are increasingly moving towards peak and capacity billing. Grid operators are looking more at your peak consumption. Whoever runs a heat pump and charges the car at the same time will pay more in future. Smart charging and load balancing therefore become even more important, and sometimes they stop you having to upgrade at all.
Cost overview: upgrade step, electrical change and estimate
Everything at a glance. These are guide prices including labour, meant to give you a feel. Always ask for a quote, because the distance to the box and the state of your installation decide a lot.
| Upgrade step | Electrical change needed | Estimated cost |
|---|---|---|
| Induction cooking | Dedicated cooker circuit, 2.5 to 4 mm² cable | 300 to 600 euros |
| Heat pump | Dedicated circuit, often three-phase or load balancing | 300 to 1,000 euros electrical |
| EV charger at home | Own circuit, thicker cable, right RCD | 400 to 1,000 euros (excl. charger) |
| Solar panels | Circuit for the inverter, sometimes an extra RCD | 150 to 400 euros extra |
| Home battery | Dedicated circuit, often three-phase | 300 to 800 euros electrical |
| Replace consumer unit | New box, fitting, RCDs | 775 to 995 euros |
| Single-phase to three-phase (electrician) | Make box and wiring suitable | 300 to 500 euros |
| Upgrade main connection (grid operator) | New connection, sometimes digging | 600 to 1,500 euros one-off |
| Complete rewire of the whole house | All new: wiring, box, sockets | 5,000 to 15,000 euros |
The numbers stack up. Go off gas with induction, a heat pump and an EV charger, and you are quickly at a new box plus three-phase plus several circuits. Factor that into your upgrade budget, because it is often the forgotten item.
Step-by-step: how to tackle a rewire during an upgrade
For those who want to do it cleverly, the order that avoids hassle:
- Finish your upgrade plan first. Which appliances are coming, and over what timescale? Heat pump, induction, EV charger, battery? Planning it all in one go is cheaper than having the electrician come back three times.
- Check your current connection and box. Look in the meter cupboard at what is there: single-phase or three-phase, how many circuits, RCD or no RCD. Take a photo for the electrician.
- Have a qualified electrician come round for a survey. They calculate your total power demand and say whether your box and connection are adequate.
- Ask about a full network with your grid operator if you suspect you have to upgrade. This can take a long time, so start early.
- Request the upgrade in good time if it is needed. The grid operator schedules it, the electrician gets the box ready.
- Have everything signed off to standard with a test certificate. Keep it, it is your proof for the insurer.
- Only connect your appliances once the installation is in order. Not the other way round.
Sounds like a lot of steps, but this is how you avoid buying a heat pump you are then not allowed to connect because your box cannot handle it.
Frequently asked questions
Do I really have to renew my whole installation for a heat pump?
Not always the whole installation, but the part you touch, yes. You need at least a dedicated circuit, often a three-phase connection and a consumer unit that meets the standard. If your box is old (screw-in fuses, no RCD), then replacing it is usually the tidier and safer choice. With load balancing you can sometimes stay on a lighter connection.
May I add a circuit in the meter cupboard myself?
No. Work in and on the consumer unit is for a qualified electrician. You cannot see a fault, but it can cause fire or electrocution, and your insurer does not cover damage from faulty work. You may replace a socket yourself (isolated), the box you may not.
What does it cost to go from single-phase to three-phase?
Budget 300 to 500 euros for the electrician to make your box and wiring suitable, plus 600 to 1,500 euros one-off for the grid operator, depending on digging. Go to 3x35A and your ongoing grid charges can rise noticeably too. Do not upgrade heavier than needed.
Is a 30 mA RCD mandatory?
On every alteration or new circuit, yes. The regulations require circuits to sit behind an RCD of no more than 30 mA, with no more than four final circuits per two-pole RCD. Single-phase circuits may not go on a three-phase RCD. If the RCD is missing entirely in your old box, then your installation is no longer safe.
My house has no earth in the bathroom, what now?
That is a serious safety problem, precisely in a wet room. Have the earthing checked by an electrician with measuring equipment. If the earth is missing, that circuit should be rewired, regardless of whether you upgrade further. Water and electricity with no earth is exactly what you want to avoid.
Do the wiring regulations apply legally if I renovate?
The standard itself is not a law, but through the building regulations it is, in practice, the standard. Existing installation you do not touch may stay. But the moment you alter or extend something, that part has to meet the current regulations. Going greener is altering, so the standard applies to that work.
How long does upgrading my connection take?
That depends heavily on your region. Normally 10 working days to 3 months. But because of full networks the waits in 2026 have grown in some areas to half a year or more than two years. Request it early if you have plans, otherwise your heat pump stands idle for months.
Getting your wiring in order is one step. But the real gain sits in the whole picture: using less, heating smartly and tackling the waste you cannot see, so that all those new appliances actually save you money instead of costing it.
I have put everything I know about bringing your bill down into the energy-saving guide. Concrete steps, no vague waffle. Have a look around: energie-verpulveraar.fredsbouwtekeningen.nl