It's 35 degrees, you turn on the air conditioning, and... the power cuts out. This is THE most common electrical complaint we get during summer on the Costa del Sol, and for many expats, it's completely baffling.
Here's the thing: Spanish electricity works differently to the UK. There's a power limit system you probably don't know about. This guide explains why it happens and how to fix it.
Why does the AC trip the electricity?
1. You've exceeded your contracted power limit (most common)
This is by far the most common cause, and it's something that confuses many expats because it doesn't exist in the UK.
In Spain, your electricity contract includes a potencia contratada - a maximum power limit. You pay a fixed daily charge based on this limit. Common limits are:
- 3.45 kW - very basic (lights, fridge, TV - AC is nearly impossible)
- 4.6 kW - basic (can run AC if careful about other appliances)
- 5.75 kW - comfortable for a small flat with AC
- 6.9 kW+ - needed for larger homes or multiple AC units
Here's the maths: your AC needs 1-2 kW, the fridge uses 0.3 kW, the hob 2 kW, your kettle 2 kW... it adds up fast. When you exceed your limit, the ICP (power limiter switch) trips automatically.
This is NOT a fault - it's the system working as designed. In the UK, you don't have this limit, which is why it surprises British expats.
2. Circuit overload
Your AC may be sharing a circuit with other appliances. Older Spanish properties weren't built with air conditioning in mind - they were designed for lights, a fridge, and not much else.
When one circuit is overloaded, the MCB (magnetotermico) trips. This is the small switch in your consumer unit that protects that specific circuit.
3. Old electrical installation
Many Costa del Sol properties were built in the 1970s-90s. The wiring was designed for a completely different era:
- Cables too thin - 1.5mm instead of 2.5mm or more
- Consumer unit too small - no space for additional circuits
- Maximum power limited - the installation can't handle modern loads
4. Faulty AC unit
Sometimes the problem is the AC unit itself:
- Faulty compressor - drawing excessive current
- Refrigerant leak - making the compressor work harder
- Dirty filters - unit struggles to cool
- Old unit - efficiency degraded over time
5. RCD trips (not the ICP)
If it's the RCD (diferencial) that trips - the larger switch with a test button - that's different. It indicates an electrical fault causing current leakage.
Possible causes:
- Moisture in the outdoor unit
- Damaged cable in the AC installation
- Internal fault in the unit
This needs professional diagnosis.
How to identify what's tripping
Understanding your consumer unit is key. Here's what to look for:
- ICP (power limiter) - Often in a separate box, sometimes sealed by the electricity company. Trips when you exceed your contracted power. This is unique to Spain.
- MCB (magnetotermico) - Small switches. Trips when one specific circuit is overloaded.
- RCD (diferencial) - Larger switch with test button. Trips when there's an electrical fault.
Quick diagnosis
- Trips only when AC + other appliances running? - Power limit issue (ICP)
- Trips even with just AC on? - Circuit problem or AC fault
- RCD trips? - Electrical fault, call an electrician
Solutions
If it's the power limit (ICP)
Quick fix: Turn off other high-consumption appliances before starting the AC. Switch off the hob, kettle, and washing machine first. Start the AC and wait a few minutes before using other appliances.
Proper solution: Increase your potencia contratada. You can request this from your electricity company (Endesa, Iberdrola, etc.). Going from 3.45 kW to 5.75 kW increases your monthly fixed charge slightly but solves the problem.
Important warning for expats:
If your installation is old, the electricity company may require a new boletin electrico (electrical certificate) before increasing your power. If your wiring or consumer unit can't handle higher power, you'll need to upgrade them first. We can help you navigate this process.
If it's circuit overload (MCB)
The AC needs a dedicated circuit with its own MCB. This means running a new cable from the consumer unit to the AC unit.
This is a very common job in older Spanish properties. It's not especially expensive or complicated for a qualified electrician.
If it's an old installation
You may need to:
- Upgrade the consumer unit
- Add new circuits
- Get a new boletin electrico
It's worth doing properly - otherwise you'll have the same problem every summer.
If it's the AC unit
- Service it: Clean filters, check refrigerant levels
- Old unit (10+ years): Consider replacing with a modern inverter model - they use less power and have smoother start-ups
CALL AN ELECTRICIAN IF:
- The RCD trips (not just the ICP)
- You smell burning
- You see sparks or scorch marks
- The problem started after a storm or heavy rain
Understanding potencia contratada
This section is specifically for expats who haven't encountered this system before.
In Spain, your electricity contract has two main costs:
- Fixed charge - based on your potencia contratada (power limit)
- Consumption charge - based on the kWh you actually use
The potencia contratada is like a speed limit for your electricity. You can check yours on your electricity bill - look for "potencia contratada" (usually shown in kW).
Typical limits and what they support:
- 3.45 kW - Lights, fridge, TV, laptop. Forget AC.
- 4.6 kW - Can run AC if you're careful. Turn off hob first.
- 5.75 kW - Comfortable for a small flat with one AC unit
- 6.9 kW - Good for medium homes or two AC units
- 8+ kW - Larger villas, multiple AC units
Increasing your limit: contact your electricity company. But be aware that if your installation is old, they may require an electrical certificate first, and you may need to upgrade your installation to support the higher power.
Preparing your home for summer
Some practical tips to avoid problems when the heat arrives:
- Check your potencia contratada - it's on your electricity bill
- Service your AC in spring - clean filters, check refrigerant
- Don't run everything at once - AC + washing machine + oven is almost guaranteed to trip
- Consider upgrading old AC units - modern inverter models use much less power
- If you've added AC units since moving in, your installation may need updating
Frequently asked questions
Why does my electricity only trip when the air conditioning is on?
Most commonly, you've exceeded your potencia contratada (contracted power limit). AC uses 1-2 kW, and if other appliances are running, you exceed your limit and the ICP cuts the power. This system doesn't exist in the UK, which is why it surprises expats.
How much potencia contratada do I need for air conditioning in Spain?
For a small flat with one AC unit, at least 4.6 kW, though 5.75 kW is more comfortable. For larger properties or multiple units, 6.9 kW or more. With 3.45 kW, running AC is nearly impossible.
Can I increase my power limit without changing the electrical installation?
It depends on your installation. If it's old, the company may require a new boletin electrico first. If your wiring can't handle higher power, you'll need to upgrade it.
Does my AC need its own dedicated circuit?
Highly recommended. AC has high consumption and significant startup surges. A dedicated circuit prevents tripping and is safer.
What should I do if the RCD trips when I turn on the AC?
If the RCD trips (not the ICP), there's an electrical fault. Could be moisture in the outdoor unit, damaged cable, or unit fault. This needs professional diagnosis.
Need help with your AC and electrics?
We help expats every summer with exactly this problem. We can assess your installation, increase your power limit, and install dedicated AC circuits. We explain everything in plain English.
If it's urgent and you're in the middle of a heatwave without AC, we have 24-hour service. There's no need to suffer in the heat.
We also handle full electrical installations and repairs for less urgent issues.
If you're in Marbella, Fuengirola, Benalmadena, Estepona, or anywhere on the Costa del Sol, give us a call - we'll tell you exactly what you need.