When off grid is worth pricing
Ask E‑REDES for a written budget to connect the property. The cost depends on the distance to the existing network and the terrain. Then price an off grid system for the same property and compare the two over ten to fifteen years, including the grid bills you would pay with a connection.
An off grid installer we spoke to in August 2026 quotes complete systems from about €9,000 to €50,000 before VAT, depending mainly on the property and how much battery capacity it needs.
Size for winter
Monthly output of 1 kWp in Ponte de Lima, 35° tilt, PVGIS
Steeper panels help in winter. At 60° instead of 35°, PVGIS gives the same Ponte de Lima system 89.8 kWh in December instead of 78.5, about 14% more, at the cost of about 7% less over the year. For a system with no grid behind it, that trade is often worth making.
What a reliable system needs
A larger panel array
Enough to meet winter demand, which means a surplus in summer that you cannot store or sell.
A battery sized for a choice you make
The installer we spoke to recommends sizing for about a couple of days of autonomy and cutting non essential loads from the first day of rain. Sizing to ride out a long wet spell with no change in habits is what makes a battery bank enormous and expensive.
An inverter built for stand alone operation
It has to run without a grid reference and manage the battery and the loads.
A backup generator
Most rural off grid homes keep one for long cloudy spells. It may run only a few times a year.
Rules still apply
Decreto‑Lei 15/2022 covers self consumption with or without a grid connection, according to the ADENE and DGEG guide. Do not assume an off grid system escapes DGEG's procedures: ask the installer to state in writing which procedure applies to your system's power. Building work on rural land may also need approval from the câmara municipal.
When off grid is the wrong answer
- A home that already has a grid connection: the grid is paid for, and a grid tied system is simpler.
- A holiday home empty for months: batteries and monitoring are harder for an absent owner.
- Air conditioning or an electric car as main loads: both raise the array and battery you need sharply.