Solar Photovoltaic — Algarve

The Algarve receives roughly three thousand hours of sunshine a year, among the best solar resource in Europe. That makes photovoltaic generation easy to justify and, for the same reason, easy to specify badly — when the resource is generous, a poor design still produces something, and nobody notices what it should have produced instead.

iHome designs and installs photovoltaic systems as part of the electrical and energy design of a property, alongside monitoring, storage and vehicle charging.

Size the array against consumption, not against the roof

The most common error in domestic solar is sizing by available roof area. It produces a system that generates a large surplus at midday which the household cannot use, and that surplus is worth far less than the electricity it replaces.

The distinction is the whole economics of the thing:

• Electricity you generate and consume yourself displaces electricity you would have bought, at the full retail price you pay.
• Electricity you export earns considerably less per kWh.

So the figure that matters is not installed capacity but self-consumption ratio — the proportion of what you generate that you actually use. A smaller, well-matched array with a high self-consumption ratio frequently outperforms a larger one that exports half its output.

Which is why we start by measuring. A house with a pool, a heat pump and daytime occupancy has a completely different profile from a holiday property empty on weekdays, and they warrant different systems. Without consumption data, sizing is guesswork dressed up as engineering.

Orientation and tilt: maximum yield is not always the objective

At the latitude of the Algarve — around 37°N — a south-facing array tilted 30 to 35° produces the greatest annual total. That is the textbook answer, and it is often the wrong one.

A south-facing array concentrates production around midday. If the household consumes most in the late afternoon and evening, much of that midday peak is exported cheaply while evening demand is bought back at full price.

Two alternatives are worth considering:

• West-facing produces less annually but shifts generation later, matching afternoon and early-evening consumption.
• Split east–west flattens the curve — less at noon, more at both ends of the day. Total yield drops modestly; self-consumption often rises more than enough to compensate.

Roof pitch is usually fixed, so in practice the decision is which roof planes to use. On flat roofs, where tilt and orientation are genuinely free, this becomes a real design choice rather than a constraint — and it is worth making deliberately rather than defaulting to south.

The details that decide whether it performs

Shading is not proportional. A chimney, a parapet or a single palm shading one module can drag down an entire string, because modules in series are limited by the weakest. Where shading cannot be avoided, module-level electronics or an inverter with multiple independent MPPT inputs recovers most of the loss. Shading should be assessed across the year, not on the day of the survey — the winter sun is far lower and casts much longer shadows.

Inverter sizing. Inverters are normally specified slightly below the array’s peak DC output. A modest DC-to-AC ratio above 1 clips a handful of hours at the top of the brightest days and improves performance for all the rest, because arrays rarely reach nameplate output in real conditions.

Heat. Panels lose efficiency as their temperature rises, typically around 0.3 to 0.4% per degree above 25°C. On an Algarve roof in August, module temperatures well above ambient are normal. Mounting that leaves an air gap behind the modules matters more here than in cooler climates, and roof-integrated systems that trap heat pay for their appearance in output.

Salt and dust. Coastal installations accumulate salt; inland, summer dust and pollen. Both reduce output gradually enough that nobody notices. Occasional cleaning recovers it, and monitoring is what tells you when it is needed rather than guessing.

Batteries: after the measurement, not before

Storage shifts surplus from midday to evening, and it is the most effective way to raise a self-consumption ratio once orientation has been optimised. It is also the most expensive component per unit of benefit, and the one most often oversized.

Battery capacity should follow from the measured evening deficit — how much energy the house actually draws after generation has stopped — rather than from a round number. A battery larger than the nightly shortfall spends its life partly empty, and a battery much smaller than it delivers less than expected.

Batteries also provide something that has nothing to do with economics: continuity through a power cut, if the system is configured for it. That requires specific inverter capability and appropriate switching, and is worth deciding at design rather than discovering afterwards that the array shuts down along with the grid — which, without that provision, is exactly what happens.

Monitoring: without it you are guessing

Every system we install is monitored — generation, consumption, self-consumption ratio, and export, recorded continuously. It answers questions that are otherwise unanswerable: whether output has dropped because of weather or because something is failing; whether the array is dirty; whether a string has gone offline; and whether the system is delivering what it was designed to deliver.

An unmonitored array that loses a string can run for months at reduced output with nobody aware. It is the cheapest insurance in the installation.

Where solar meets the rest of the house

A photovoltaic array on its own is a generator. Connected to the rest of the property’s systems, it becomes something more useful.

Deferrable loads move to the generation peak — pool filtration, water heating, dishwashers. Vehicle charging absorbs surplus that would otherwise be exported at low value. Battery charging is scheduled around forecast and consumption rather than simply filling whenever there is sun. And where the property has KNX or Control4, all of it appears in the same interface as everything else, rather than in a separate app that nobody opens after the first month.

These interactions are where most of the real value sits, and they depend on the systems being designed to see each other. That is a decision taken at the beginning; it is difficult and expensive to add between systems bought separately from different suppliers.

Registration and compliance

Self-consumption installations in Portugal must be registered, with requirements that depend on the installed capacity and on whether surplus is fed to the grid. We handle that process as part of the installation.

How a project runs

1. Consumption analysis. Existing bills, and where possible a period of monitoring, to establish the real profile rather than an assumed one.
2. Site survey. Roof structure and condition, available planes, shading across the year, cable routes, and where inverter and any storage will live.
3. Design. Array layout, orientation strategy, inverter and storage specification, expected generation and self-consumption, and the electrical work required.
4. Installation and commissioning. Mounting, DC and AC work, protection, monitoring, and testing.
5. Registration and handover.
6. Monitoring and maintenance.

Working with iHome

We have been designing electrical systems in Algarve properties since 2006, and we are an official Control4 dealer and certified KNX partner, nationally awarded for our KNX work. Solar is specified alongside the electrical installation, energy monitoring and vehicle charging rather than as a separate purchase, because that is where the systems either reinforce each other or work against each other.

Call (+351) 289 090 900 or email geral@ihome.pt to discuss a project.