Author
Adam Millington is the founder and co-owner of Marblanc Solar. He is a fully qualified electrician with a QQI Level 6 Advanced Certificate Craft –Electrical and a Masters in Sustainable Electrical Energy Systems at the Technological University Dublin.
Want a complete guide to installing solar panels in Spain?
You’re in the right place.
Last month, a Marblanc Solar client in Manilva sent us their latest electricity bill showing a €0 electricity cost. They’d even earned €9.44 in credit for their virtual battery.
Unfortunately, the solar panel industry in Spain is full of false promises to “eliminate your energy bills”.
I don’t want you to be misled.
That’s why in this post, I’m going to teach you:
The truth about savings that solar installers never admit
Easy calculations to figure out how many solar panels you need
Whether you need a solar battery (and how to cut electricity costs to €0 without one)
Why the virtual battery is key to maximising your savings
Let’s get going!
Get a Free Solar Survey Worth €159
Want an in-depth solar proposal tailored to your property?
It will cost you at least €159 to hire a survey engineer, scan your property with a drone, and pay for the best solar design software (Pylon).
Click below to have Marblanc Solar do it all for free in 1-3 working days.
Free Solar SurveyStep One – Understand what a “€0 Bill” Actually Means
In Spain, it’s not possible to cut your electricity bill to €0.
Spain’s government body for renewable energy (IDAE) explained in 2023 that you can’t cancel standing charges. You can only cut your electricity costs to €0.
This is clearly seen in our client’s bill above.
You’ll notice that:
- They bought €50.82 worth of electricity
- They sold €60.26 worth of electricity back to the grid
- They earned €9.44 in credit for their virtual battery
- They paid €40.04 in standing charges, taxes and “other” costs
Why am I telling you this?
Because I don’t want you to fall for the common sales tactic: an installer promises you savings based on cutting your entire electricity bill to €0.
The overall savings have to add up.
As you’ll see below, the client in this case study is on track to save €2,228 in the first year after going solar – so it’s still very worth it, despite the standing charges.
Key Takeaway
Factor in a residual cost of €20-60 a month, even if your electricity costs are €0.
Step Two – Check Your Electricity Usage
At Marblanc Solar, every Free Solar Survey begins by asking the client for their electricity bill.
Why?
Because we’re looking for three pieces of information:
- Your average electricity costs over the past 12 months
- Your average electricity consumption in kWh
- Your seasonal consumption patterns
This information makes it easy to understand how much solar power you need to cut your electricity costs to €0. (See Step 5.)
But there’s one missing piece.
You must understand how much electricity you’re consuming after dark.
If you’re not getting a solar battery, then you need to account for selling more electricity to the grid during the day than you’ll buy back at night.
For our client in Manilva, we recognised the client was using electric power at night to climatise the property in summer and winter. This information was important in understanding how many solar panels the client needed. (See Step 5.)
Key Takeaway
Factor in nighttime electricity use when considering the best solar installation for you.
Step Three – Sanity Checks
Before proceeding, you need to answer the following questions:
- Will community rules affect your installation?
- Is your electrical intake single-phase or three-phase?
- Is your electrical board old or underspec’d?
Let’s look at each of these in turn.
Community rules
If your property is part of an urbanisation or community of owners (comunidad de propietarios) there may be rules on solar panels.
We’ve had clients unable to install solar panels on their roof at an angle. The panels had to be flat to avoid visual disruption.
Electrical intake
Your electrical intake may limit the size of a solar installation on your property.
For example, the client in this case study had a single-phase intake. We were unable to install a system beyond 12 kW of capacity.
Luckily, the 11.9kW system we installed was enough!
(The picture above shows a three-phase intake.)
Electrical board
Your solar system is only as safe as the electrical board it connects to.
An underspec’d board can lead to nuisance tripping, overheating, or even a fire risk. But replacing your electrical board adds costs to your project.
So it’s worth factoring in.
If you’re not sure, contact Marblanc Solar for an expert’s opinion.
Key Takeaway
Companies in Spain can and do install faulty or illegal systems. These three sanity checks help you move forward with confidence.
Step Four – Assess Your Available Installation Space
Ask yourself these important questions when assessing your roof’s suitability for solar panels:
- What’s the orientation?
- Is there shading?
- Is the roof in good condition for solar panels?
- How much space do you have?
Let’s look at each of these.
Orientation
In southern Spain, solar panels produce the most electricity when facing south and angled at 25-30° against the horizontal.
Not every property has an obvious area to install panels.
But in this case, the client’s south-facing flat roof made it simple for our software to select the best available space.
Shading
Failure to consider shading can lead to an underperforming system.
Studies have shown that tree shading can cut solar output by 10-20% a year. Even small shadows can knock out the production for whole sections of a panel.
At this 13-panel solar installation in Alhaurín el Grande, we had to install optimisers and carefully plan the solar system around a palm tree in the garden.
Roof condition
There are horror stories in Spain of homeowners waking up to find their solar panels in the garden – along with half their roof.
It seems crazy to me that installers don’t check for this.
We use a survey engineer to look at the roof’s age, condition and suitability for the weight of solar panels. We will add the costs of strengthening a roof to the client’s quote if necessary – but I don’t know another installer who does.
Look for signs like:
- Sagging
- Cracked or warped beams
- Damp patches
- Rot
- Leaks
- Loose tiles
- Cracked tile
If you’re not sure about your roof, contact Marblanc Solar for an expert’s opinion.
Viable space
Measuring the viable space for solar panels can get complex.
But if you’re designing a solar energy system to cut your electricity costs to €0, you can’t rely on the eye test alone. It’s not reliable enough.
That’s why Marblanc Solar offers every new client a Free Solar Survey. We’ll fly a drone to scan your roof and then use AI-powered solar design technology to determine the best placement for panels – with orientation and shading factored in.
This method can lead to creative solutions.
For example, at this property in Fuengirola, our AI recommended 12 panels on the roof and 5 panels on the carport to cut electricity costs to €0.
Key Takeaway
Solar panels are rarely installed facing due south at an angle of 25-30°. You’ll need to understand your available space before determining how many panels you need.
Step Five – How Many Solar Panels Do You Need?
There’s a calculation many installers in Spain use to understand how many solar panels you need.
Here’s how it works:
- Take your average monthly electricity consumption (Step Two)
- Divide it by 30 for your daily average consumption
- Divide by peak solar hours in your region (5.82 in Marbella)
- Divide again by the solar panel wattage
Here’s how that looks with the installation in this case study:
- ~900 kWh average monthly consumption
- ~30 kWh daily consumption
- ~5.15 kW capacity required
- ~9 solar panels with 595W capacity required
This can work in theory.
But in our original proposal, we recommended our client in Manilva install 18 solar panels – and in the end, he asked for 20 solar panels.
Why such a difference between theory and reality?
Because the calculation can’t account for nighttime consumption. Since our client in Manilva didn’t want a solar battery, we recommended over-sizing the system to maximise his chances of cutting electricity costs to €0.
And one more thing…
Marblanc Solar uses the AI-powered solar design platform Pylon to calculate each client’s expected savings. So we can get a much more accurate idea of what you need, than with a basic calculation.
Key Takeaway
The best way to determine how many solar panels you need is using solar design software, such as Pylon. You can see the pricing here.
Get a Free Solar Survey Worth €159
Want an in-depth solar proposal tailored to your property?
It will cost you at least €159 to hire a survey engineer, scan your property with a drone, and pay for the best solar design software (Pylon).
Click below to have Marblanc Solar do it all for free in 1-3 working days.
Free Solar SurveyStep Six – Decide if You Need Add-Ons
Add-ons like solar batteries, backup boxes and EV chargers increase your installation costs.
But you may need to factor them in.
The Manilva client in this case study did not need a solar battery, backup box or EV charger – but I’ll cover them quickly in case they’re relevant to you.
Solar batteries
If your property consumes a lot of electricity at night, you’ll need a solar battery to cut your monthly costs to €0.
You may also need a battery if you have appliances that create short, high-power spikes in demand. Heat pumps, EV chargers and electric water heaters can pull a lot of power in bursts, especially when they switch on.
A battery can help smooth these spikes by supplying extra power instantly, so you import less electricity from the grid during peak moments.
There are other reasons too.
Some clients want energy independence from the grid as much as possible – our client in Alora (pictured above) installed 14 solar panels and a 10kW solar battery to cut electricity costs to €0 and have no grid reliance at all.
Backup boxes
Backup boxes keep essential circuits in your home powered during a blackout by switching your solar system into backup mode.
They won’t affect your monthly electricity costs.
But they can be a crucial add-on if you live in an area with frequent power cuts and you want lights, Wi-Fi, fridges, medical equipment, or security systems to keep running.
EV chargers
EV chargers are a popular add-on because they let you charge your electric car much faster than using a standard household plug.
They’re an important consideration if you’re planning to charge an electric car at home, because EV charging can become one of your biggest new electricity uses.
We often see clients decide to install solar panels straight after buying an EV – and in that situation, you can’t size your system based only on past consumption.
Instead, you need to model your new usage properly.
This is where solar design software helps, because it can estimate how EV charging will change your monthly bills and what size system you need to get back to €0.
That’s exactly how we helped a client in Fuengirola cut their electricity costs to €0 after installing solar panels and a 7.4kW EV charger.
Key Takeaway
Consider whether you want add-ons early, as they’ll influence the system cost and power needed to cut your electricity costs to €0.
Step Seven – Does the Brand of Solar Equipment Matter?
The truth is that the brand of solar equipment might not be felt for years to come – for example, if the equipment starts to wear out.
Instead, we recommend you compare equipment based on key features.
We’ll look at some of these below.
Solar panels
- Efficiency – Higher efficiency can help when roof space is tight.
- Degradation – Better panels lose output more slowly over time, which protects long-term savings.
- Warranties & product guarantees – Most solar panels today come with 25-year warranties.
- Aesthetics: All-black panels can look cleaner, but the output is often much lower than standard monocrystalline panels.
For the Manilva client in this case study, we used monocrystalline JA Solar panels because they were cost-effective and came with 25-year warranties.
Solar Inverters
- Compatibility – It must match your supply (single-phase or three-phase) and your system size.
- Monitoring – A good app makes it easy to track production, consumption, and savings.
- Reliability + warranty + support – This is where brand reputation really matters, because inverter issues cause the most disruption.
At Marblanc Solar, we almost exclusively install Huawei inverters, batteries and EV chargers because they’ve proven extremely reliable in our projects. They also have strong built-in safety protections – for example to reduce fire risk or support better backup functionality.
The Huawei monitoring app makes it simple to track your system day-to-day.
You can click here to read more about why we rate Huawei solar inverters so highly.
Key Takeaway
Solar brands like Huawei come with premium features and longevity – but they can also increase the total costs of your system.
Step Eight – Get a proper solar proposal
Most homeowners in Spain will compare 3-4 solar quotes before choosing an installer.
That’s normal.
In this case, the client chose Marblanc Solar – and we overdelivered on our promise to cut their electricity costs by 87%, helping them reach €0 instead.
Let’s go over the key elements we included in the proposal for this client.
Hopefully, these will help you sort the good proposals from the bad.
- Savings – Estimated monthly and annual savings calculated from electricity usage costs, with clear wording that these figures don’t include standing charges and taxes.
- Warranties – 25-year equipment warranties plus a 25-year workmanship warranty (rare, because it makes the installer responsible for the ongoing quality of the install).
- Bill comparison – A before-and-after monthly bill comparison based on the client’s historical electricity bills, not assumptions.
- Layout plan – Recommended panel placement graphic produced from a drone scan and AI-powered solar design software.
- Returns – Investment metrics that show the economics clearly: IRR (20.5%), total ROI (366%), NPV (€40,281.98), and a discounted payback period (5–6 years).
- Itemised quote – A transparent breakdown covering equipment, materials, labour, legalisation, testing & commissioning, and admin. Click here for information on the costs of solar panels in Spain.
- Environmental impact – A simple annual impact summary (e.g., avoiding the equivalent of burning 3,044kg of coal per year, similar impact to planting 161 trees per year).
Key Takeaway
The care taken to prepare your solar proposal is a reflection of the care taken to size your system, and the after-care support.
Step Nine – Get a Virtual Battery
A virtual battery is a scheme where the electricity you export to the grid earns credit, and that credit can be used to offset electricity you buy later.
In this case, this credit got our client’s electricity costs to €0.
Without the virtual battery option, they would have paid €50.82 more in the bill – and their €69.26 worth of unused solar electricity would have been wasted.
This shows how valuable a virtual battery is.
When comparing virtual battery providers, compare these four points:
- Export rate – How much credit you get per kWh you export versus what you pay per kWh you import. In this example, the client paid €0.153/kWh for grid electricity and earned €0.06/kWh for exported electricity. That gap is significant, but it’s often normal.
- Subscription cost – Some providers charge a monthly fee. In this case, the client pays €2.04/month to access the virtual battery. Not every provider charges a subscription.
- Credit expiry – Check how long you can keep the credit. Some providers only let you use credit within the same year, while others allow credit that never expires.
- Credit timing – Find out when the credit is applied. In this case, the client can’t use the credit earned in the same month to reduce that month’s bill. It can only be used from the following month onwards.
Key Takeaway
Switch to a solar feed-in tariff with a virtual battery as soon as possible.
Step Ten – post-installation support
This is the final step!
And it’s worth highlighting, because our post-installation services helped this client cut their electricity costs to €0 just three months after installing solar panels with Marblanc Solar.
Not every solar installer offers meaningful after-sales care.
But here’s what we offered the client in this case:
- Legalisation & paperwork – We handled the paperwork needed for a legal installation and to access export compensation, feed-in tariffs, and virtual battery deals.
- Two-week monitoring – We monitored system performance and the client’s electricity consumption, and offered to return to install plug timers and optimise appliance usage. In many homes, small changes are the difference-maker. For example, a pool pump running between 1am and 8am (see screenshot above) is an unnecessary use of power that could be shifted to daytime solar to save more.
- Free annual servicing – We offered free annual servicing for the first three years to keep the system running at peak performance.
- Virtual battery comparison – We help every client compare virtual battery providers so they can find the best deal for their usage and goals.
The truth is, many installers stop at the day the panels go on the roof.
Legalisation support, monitoring, optimisation, and tariff/virtual battery guidance are often missing – even though they can be the steps that turn “good savings” into €0.
We hope this case study shows why after-sales care matters.
The install gets you generating power, but the post-installation support is what often makes €0 electricity costs achievable in real life.
Key Takeaway
Carefully look at your solar installer’s post-installation services.
Get a Free Solar Survey Worth €159
Want an in-depth solar proposal tailored to your property?
It will cost you at least €159 to hire a survey engineer, scan your property with a drone, and pay for the best solar design software (Pylon).
Click below to have Marblanc Solar do it all for free in 1-3 working days.
Free Solar Survey