Solar panel calculator: how many panels do you need for your home?

It estimates that the photovoltaic power and the number of panels based on your home’s annual energy consumption, the region of Spain, the orientation of the roof and the percentage of your energy consumption you wish to cover. You’ll be given the kWp, the number of panels, the approximate surface area, annual output and a suggested inverter.

Property details

How is it calculated?

Start from the specific output in your area (annual kWh per kWp installed, according to PVGIS), adjusted for orientation, tilt and shading. The required power is the annual consumption multiplied by the percentage to be covered and divided by that specific output. The number of panels is rounded up, and the inverter is sized with a DC/AC ratio of 1.2, which is standard for self-consumption.

Tips

• Without a battery, direct self-consumption stands at around 30–50 %: the rest is sold as surplus at a lower price. That’s why it’s not worth oversizing the system too much if you’re not going to install a battery.
• With the battery, covering 100–130 % of consumption allows the battery to be charged during the day and enables 80–90 % of self-consumption.
• East-west roof: total output is 10 % lower, but the curve is flatter and direct self-consumption is improved.
• If you own or are planning to buy an electric car or an air-source heat pump, add their estimated consumption to your annual total.

Continue with: string configuration and MPPT validation, how much does it cost to install solar panels y frequently asked questions.