How many solar panels do I need to supply my house?

How many solar panels do I need?

It is estimated that a conventional home needs between 4 and 18 photovoltaic panel modules to be supplied, but this may vary from one home to another. In order to make a more precise calculation of the number of panels you need to install in your home and thus be able to amortize the initial investment, it is important that you know the 4 main factors that are going to be essential in this calculation:

• The energy consumption of your home 

This is one of the most important factors to know how many solar panels you will need in your photovoltaic installation since the exact number of panels will be able to be correctly determined based on your consumption. In order to carry out this calculation, you must review your annual consumption and distribute the energy expenditure according to the different months of the year.

According to Red Eléctrica de España (REE) , the monthly consumption of kWh in a Spanish home is around 270 kWh, that is, around 3,272 kWh/year. However, this will vary depending on the location of the property, the number of inhabitants in the house, consumption habits or the number of electrical appliances. If you want to make a precise and individualized calculation of your consumption, it is recommended that you read your electricity meter.

• The area available for installation of solar panels

The solar panels that you are going to install, also known by the name of photovoltaic modules, must be adjusted to the available space of your building and also to its orientation. The best orientation of a photovoltaic installation is towards the south, since in this way, sunlight falls perpendicularly on its surface and a better use of light is achieved.

To make sure that there are no energy losses and that the orientation of your house is correct, you can check its orientation with a compass. Once you have located the orientation of your roof, you can determine the number of modules to install. For a well-oriented roof, a power of 150Wp/m2 (Watt Peak/square meter) is estimated. If when doing this check you realize that the orientation is not the most appropriate, you can ask for advice to install them in another place or change their orientation.         

• Hours of sunshine versus your consumption 

The best performance of the installation is obtained during the central hours of the day, since these are the hours in which your solar panels will produce a greater amount of energy. If these hours coincide with those in which you consume the most electricity, you will be making the most of your installation. However, if you need to consume more energy at other times, you can opt for surplus compensation mechanisms.

The electricity tariffs that allow you to compensate for the excess energy produced by the solar panels, will allow you to use electricity during hours when the panels are not producing energy. In addition, it is important to mention that if you produce more energy than you consume, some marketers will compensate you for the energy not consumed, thus benefiting from a discount on your bill.     

• Rate contracted with the electricity supplier 

It is recommended to hire a rate with hourly discrimination, that is, one that divides the day into three periods (Valley, Plain and Peak). These types of rates have a schedule with a higher price in the Peak and Valley periods and for this reason, during these sections it is interesting to use the solar energy generated by the photovoltaic panels.

In this way, during the sections with the highest price, the kWh produced by the solar panels would be used to a large extent and if the energy demand had not been fully covered with the photovoltaic installation, the reduced price of the Valley rate would be used. .

Hourly electricity rates or also known as variable rates , are the most suitable for self-consumers since the prices are those set by the wholesale market and are at cost price. In addition, they are transparent and public rates that can be consulted on the OMIE page (Electricity Market Operator,  www.omie.es ). Knowing the price of electricity per hour together with a variable rate will help you reduce your electricity bill.