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Guide

How to compare solar quotes in Portugal

Two solar quotes can be €600 apart and still not describe the same system. Put every quote on the same four numbers: total kWp, price per kWp, usable battery kWh and warranty years for each part, in writing. Then run the eight checks below before you sign anything.

Updated 1 October 2026

The four numbers

  1. Total kWp, not the panel count

    Twelve panels at 400 W is 4.8 kWp. Twelve at 550 W is 6.6 kWp, 38% more capacity behind the same panel count.

  2. Price per kWp

    Divide the price by the kWp. €6,600 for 4.8 kWp is €1,375 per kWp; €7,200 for 6.6 kWp is €1,091 per kWp. The dearer quote is the cheaper system.

  3. Usable battery kWh

    The ADENE and DGEG guide advises using most batteries only between about 20% and 80% of charge, so they last longer. Set up that way, a 10 kWh battery gives about 6 kWh. Compare on the usable kWh the installer states in writing.

  4. Warranty years for each part, in writing

    Panels, inverter, battery and installation carry separate warranties. For panels, ADENE and DGEG advise at least 80% of the power guaranteed after 25 years.

Eight checks before you sign

  1. Panel brand, model and wattage. The quote should name each one and link a datasheet. A model code with no brand is a question to ask.
  2. Inverter type. String, hybrid or microinverters. Only a hybrid inverter takes a battery now or later, and only some keep the house running in a blackout.
  3. Roof orientation and tilt. PVGIS puts a south facing roof in Ponte de Lima at 1,412 kWh per kWp a year; the same roof facing east gives 1,108 and facing west 1,137, about 20% less. A quote with no orientation has no reliable payback.
  4. A yield estimate for your address. Ask which tool produced it. PVGIS is free and public, so you can check it yourself.
  5. Who registers the system with DGEG. For almost every home the installer submits a prior notice on the DGEG portal before installing. Ask the quote to say so, and see the DGEG registration guide.
  6. The installer's accreditation. ERSE lists it as the owner's duty to check that the installer is a recognised installation entity or responsible technician (Lei n.º 14/2015 and Decreto‑Lei n.º 96/2017). Ask for the number.
  7. Civil liability insurance. Registered systems need it, according to the ADENE and DGEG guide. Ask who arranges it.
  8. Who you call in three years. A named contact or a service agreement, not a general email address.

Warning signs

  • No price per kWp and no way to work it out.
  • Battery capacity given only as the headline figure.
  • "DGEG included" with no list of what that covers.
  • A quote valid for 24 or 48 hours with no reason given.
  • No site visit, no roof assessment and no orientation stated.

How Minho Solar uses the four numbers

When you ask for quotes, we ask every installer for the same four numbers, so the quotes you receive line up. If one arrives without them, send it to hello@minhosolar.com and we tell you what to ask.

For a longer list of warning signs with explanations, use the quote red flags tool.

Sources

Other guides

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