An off-grid solar system has four parts: panels, a charge controller, a battery bank and an inverter. Most installers in Spain fit grid-tied rooftop systems, where the grid covers any shortfall. Off-grid is a different job: the system has to carry the house through a run of cloudy days in January, so it is sized from your use, not from your roof.
Start with a list of what you’ll run and for how long, then add the things people forget: a borehole or pressure pump, a fridge-freezer in a 40 °C summer, a water heater. Our solar calculator gives you a starting size to compare against each installer’s quote.
Batteries are the most expensive part and the one that wears out. Lithium iron phosphate (LiFePO4) is now standard; ask for usable capacity, rated cycles and the warranty terms. Inverter brands matter too, because you want an installer who can service the one they fit.
Questions to ask before you sign
- How many off-grid (stand-alone) systems have you fitted?
- Can you size the system from my appliance list?
- What battery chemistry, usable capacity and warranty are you quoting?
- Which inverter brand, and do you service it yourselves?
- What does the price include: fitting, cabling, certificates?