Solar in plain English

Every term you'll see on a Portuguese solar quote, translated and explained. From UPAC and DGEG to hybrid inverters and self-consumption.

12 terms

: Kilowatt peak (kWp) is the rated capacity of a solar panel system under standard test conditions (1000 W/m² of sunlight, 25°C cell temperature). A 5 kWp system produces 5 kilowatts at noon on a clear day in ideal conditions. In the Minho, expect roughly 1,350 to 1,450 kWh per kWp per year in actual production.
: The inverter converts the direct current (DC) produced by solar panels into alternating current (AC) that your home and the grid use. A string inverter is one box for all panels. Microinverters sit under each panel individually. Hybrid inverters can also manage a battery.
: A hybrid system pairs solar panels with a battery through a single hybrid inverter. When the grid fails, the battery keeps your essentials running. Standard grid-tied systems are legally required to shut down during a blackout, even when the sun is shining. This is what caught thousands of homeowners out on 28 April 2025.
: Self-consumption is the fraction of your solar production that you use immediately rather than exporting to the grid. Higher self-consumption means better savings, because exported power is paid at a lower tariff than imported power. Batteries and shifting usage to daytime both increase self-consumption.
: DGEG (Direção-Geral de Energia e Geologia) is the Portuguese energy regulator. Every grid-tied solar installation must be registered with DGEG and your distributor (usually EDP Distribuição). The paperwork is in Portuguese and the process takes 30 to 90 days. Many installers leave it to you.
: PVGIS (Photovoltaic Geographical Information System) is a free tool from the European Commission that estimates solar production for any location in Europe. It accounts for local irradiance, roof orientation, tilt, and shading. Honest solar quotes in Portugal should be based on PVGIS data for your specific postcode, not national averages.
: UPAC (Unidade de Produção para Autoconsumo) is the legal classification for a self-consumption solar system in Portugal. Systems under 1 kWp have simplified registration. Larger systems require a full UPAC registration with DGEG. Your installer should handle this, but you are legally responsible for confirming it is done.
: The payback period is the time it takes for your cumulative energy savings to equal the upfront cost of the system. In Northern Portugal, a grid-tied system typically pays back in 7 to 9 years. Adding a battery extends payback to 10 to 12 years, but adds blackout resilience. The 2025 VAT change from 6% to 23% pushed payback out by about 18 months.
: A grid-tied system is connected directly to the EDP grid with no battery. It is the cheapest option and the most common installation in Portugal. By law, grid-tied inverters must shut down the moment the grid fails, to protect line workers. This means zero power during a blackout, even when the sun is shining.
: Irradiance is the power of sunlight hitting a surface, measured in watts per square metre. Annual irradiance is the total energy over a year, measured in kWh/m²/year. The Minho receives roughly 1,350 to 1,450 kWh/kWp/year, about 30 to 40 percent less than the Algarve.
: VAT (IVA in Portugal) on residential solar installations was reduced to 6% in 2022. That reduced rate ended mid-2025. Standard 23% now applies to most residential solar. Always check the VAT line in any quote; some installers still quote at 6%, which makes the price look lower than it actually is.
: EDP (Energias de Portugal) is the largest electricity supplier and distributor in Portugal. EDP Comercial sells you electricity. EDP Distribuição operates the grid. Your solar system connects to the EDP distribution network. Your monthly bill shows both supply and network charges separately.