How many solar panels do you need to power a house in Spain?
It depends on your property size and how much electricity you use. As a rule of thumb:
- A townhouse typically needs 10–15 solar panels
- A medium villa needs 15–20 solar panels
- A large villa needs 20–35 solar panels
- A luxury villa can need 35+ solar panels
What You Need to Know Before Counting Panels
Most people ask how many panels they need. But the better question is what size system (in kW) you need. Panel count follows from that.
The standard panels we install for residential solar panel installations today output 650W each. Some clients choose all-black panels for aesthetic reasons — these can output 420W each.
Let’s look at the difference that can make:
- A 10kW system using 650W panels needs 16 panels
- A 10kW system using 420W panels needs 24 panels
In other words, you could have 16 panels but generate the same power as your neighbour with 24 panels. The system size is what counts.
How Many Solar Panels Do I Need to power a villa in spain?
Across our solar installations on the Costa del Sol and Costa Blanca, system size breaks down clearly by property type.
Here’s a quick overview with real examples.
| Property Type | Avg Monthly Bill | System Size | Real Installations (and # of solar panels) |
| Townhouse | €80–120 | 5–8kW | Mijas (11 panels) · Fuengirola (12) · Calahonda (14) |
| Medium villa | €150–250 | 8-15kW | Alora (14) · Sotogrande (19) · Fuengirola (17) |
| Large villa | €400–600 | 15–20kW | Sotogrande (33) · Marbella (31) |
| Luxury villa | €1,000-3,000+ | 20–35kW | Nueva Andalucía (39) · Benahavís (61) |
These are starting points, not guarantees. Every property is different.
If you’d like to understand the system size you need (in kW) and a precise solar panel count, you can book in your Free Solar Survey. You’ll get a system design built with the world’s leading solar design tool and site visit from a qualified electrician – that’s €250 worth of value for free.
What Factors Affect How Many Solar Panels You Need?
Panel count is an output. These are the inputs that determine it.
Roof orientation
South-facing roofs produce the most energy in Spain. Southeast/Southwest orientations lose 1–4% of efficiency.
East or west-facing roofs can lose 10–30% of output. That means more panels are needed to reach the same system size. North-facing roofs are not recommended — the output loss makes most residential installations unviable.
Roof tilt angle
The angle of the panels affects how much sunlight they capture throughout the day. Panels mounted flat at 0° lose 10–20% of annual output compared to the optimal tilt for the local latitude.
Tilt is set at installation to a fixed year-round compromise angle. It cannot be adjusted after the fact without significant cost.
Panel type
Standard 650W panels deliver more output per unit. All-black 420W panels are smaller and suit certain roof configurations or client preferences on aesthetics. The choice affects panel count, total cost and roof area needed for installation.
Location
Spain is one of the sunniest countries in Europe – peak solar hours vary only slightly by area across southern and eastern Spain. But it directly affects how much energy a system produces per day.
| Location | Avg Daily Peak Solar Hours |
| Campo de Gibraltar | 6.0 |
| Granada | 5.9 |
| Málaga | 5.82 |
| Alicante | 5.7 |
| Valencia | 5.7 |
Source: PVGIS 2023 data
A system in Sotogrande, in Campo de Gibraltar, produces slightly more energy per panel per day than the same system in Valencia. For properties at the higher end of their panel range, location is often the reason.
How Do I Calculate What Size Solar Energy System I Need?
I see a lot of clients using ChatGPT to size their system. This can create a lot of errors (see below). If you’re serious about figuring out the size system you need then I recommend you book in a Free Solar Survey – it’s free and is the most accurate in Spain.
That said, there is an easy way to get a ballpark figure.
Here are the steps:
- Grab your latest electricity bill.
- Find the bar chart showing your monthly consumption in kWh for the past year.
- Find the tallest bar.
- Work out the electricity consumption for that tallest bar (in kWh)
- Divide it by 30 to get your daily usage (in kWh)
- Divide that by the average peak solar hours for your area
- The result is the minimum system size in kW your home needs
The formula:
- Highest monthly kWh ÷ 30 = daily kWh needed
- Daily kWh ÷ local peak solar hours = minimum system size in kW
System Sizing Example – Medium-size villa in Marbella
| Step | Calculation | Result |
| Highest monthly usage | — | 1,800 kWh |
| Daily usage | 1,800 ÷ 30 | 60 kWh/day |
| System size needed | 60 ÷ 6 | 10 kW minimum |
Always use the highest month. Sizing off an average month or a low winter month is how undersized systems get sold.
This formula gives a minimum. We size every system above the minimum – to account for increases in usage that come once a client sees their electricity is coming free from the sun.
Our Free Solar Survey produces a far more accurate figure. Our engineers run every month of your bill through the world’s leading design software and model year-round system performance, not a single-month estimate.
When Do I Need a Solar Battery?
Panels generate power when the sun is up. But you’ll still be paying for night-time electricity usage.
There are two options:
- Install a solar battery to store your energy on-site.
- Get a virtual battery deal to credit you for excess daytime generation and use this to offset night-time grid usage.
We switch every Marblanc Solar client over to a virtual battery deal. In some cases, when we’re installing an oversized system, you can eliminate your electricity costs – like happened for this 10.115kW solar installation in Fuengirola.
But be warned.
The virtual battery pays around 6 cent per kWh exported. Importing from the grid at night costs around 16–18 cent per kWh. So storing energy in a physical battery saves more per kWh – but it also costs more upfront.
| Night-time electricity use | Physical battery needed to eliminate bill? | Virtual battery enough to eliminate bill? |
| AC running at night | ✓ Yes | ✗ No |
| Electric car charging overnight | ✓ Yes | ✗ No |
| Pool heater running at night | ✓ Yes | ✗ No |
| Pool pump only | ✗ No | ✓ Yes |
| Minimal usage – lights, TV, devices | ✗ No | ✓ Yes |
| Power cut protection required | ✓ Yes | ✗ No |
| Early dinners, low evening usage | ✗ No | ✓ Yes |
Clients who want to eliminate their bill entirely almost always need a physical battery. Clients focused on reducing their bill – rather than eliminating it – often find a virtual battery is the right starting point.
In our experience, many clients install panels first and return for a battery within the first year. It can be worth seeing how your system performs before deciding whether the battery is worth the cost.
What Can Go Wrong If a System Is Sized Incorrectly?
In the last week alone, eight clients contacted me about existing installations that were not delivering their promised savings. This can happen for many reasons. Here are the most common.
Systems sized off Low-Consumption Month
If an installer sizes your system on a low-consumption month, it underperforms every high-usage month. We size every system off the peak month as we’re more confident to deliver a system that can eliminate your bills.
No buffer for future consumption
Once clients go solar, usage increases. It is human nature – the electricity is coming from the sun. An undersized system catches them out. We always ask clients how much more they might use their AC (for example) and then build out a system to eliminate their bills based on past + future consumption.
Panels placed in shade
You won’t believe me. But I have seen panels installed in the shade of the property they were meant to power. It’s an extreme example of what can and does go wrong.
Not many people know that even shading from a tree can seriously affect your power generation – shading pulls down the output of the entire string it sits on. We drone-map every roof before installation, tracking sunlight hour by hour across the full day. We’ll then add optimisers where shading cannot be avoided to maintain output.
Choosing the “cheapest quote”
Low-cost installers underspec systems to hit a price point, overpromise savings, and in some cases go out of business after installation. We have rebuilt systems from other companies – rewiring, adding missing electrical protections, and bringing installations up to proper specification. At cost to the client who already paid once.
Getting the panel count right is only half the problem. A correctly sized system on the wrong roof sections still fails.
Want to Find Out How Many Panels You Need for Your Property in Spain?
I recommend you book in a Free Solar Survey with my team at Marblanc Solar.
A Free Solar Survey includes:
- On-site inspection by a qualified electrician or survey engineer
- Drone roof mapping
- Shading, orientation and tilt analysis
- Inspection of past electricity Q&A
- Thorough Q&A about desired future consumption
- Solar proposal using the world’s leading design software
- Itemised quote & financial analysis
It’s free and the total value is estimated at €250.
Can’t I Just Use ChatGPT?
I see homeowners use AI all the time to estimate their system size. But here’s the thing. ChatGPT doesn’t know your roof angle, orientation or how shading will affect performance.
AI is only as good as the information you give it.
For that you need the drone scan and specialist software. This is why I recommend you get the Free Solar Survey – once you have the accurate data, you can feed it into AI and it will be much more valuable for you.
