“How do I know how many solar panels my house needs? How do I calculate it? And what factors do I need to take into account?”
The number of solar panels that their house will need is one of the issues that most concerns our customers, as this will determine the total price of the photovoltaic installation, and is an essential factor if you want to get the most out of the system.
Here at MyGreenHouse, we want to let you know everything you should bear in mind.
Energy consumption is the key
The number of solar panels you would need for a conventional house (e.g. a single-family house) ranges between 4 and 18 modules. The range is so wide because it depends on several factors, the most important being how much energy you need.
To find out how much energy you normally consume, you should calculate the kW consumed annually, although ideally you should know both the energy consumption (expressed in kWh/day) and what percentage corresponds to daylight hours and how much to the nighttime hours.
Generally speaking, installations requiring less than 2000 kWh are considered low consumption, and 2-4 solar panels may be sufficient. However, in this case, we would not recommend installing, as the payback time is usually longer, between 10 and 12 years.
For energy consumption of between 2000 and 4000 kWh, you would need between 4 and 6 solar panels, while for an average consumption of 4000 to 6000 kWh, between 7 and 9 are recommended. To find out if it will be cost-effective for you, we offer a free personalised study, as, in many cases, especially for consumption of less than 4000 kWh/year, it may not be worth it; it all depends on the home’s energy consumption.
Finally, for high consumption (8000 kWh and upwards), you will need between 10 and 16 solar panels.
Other key factors for the correct evaluation of a photovoltaic system include:
In Spain, each province receives varying degrees of sunlight, so the number of solar panels you need to install will depend on the area you live in.
For example, if you live on the plateau or in the south and have a south-facing roof, you will need fewer solar panels to produce the same amount of energy as someone who lives in the north, which provides, on average, 10% less energy from the panels.
- Roof orientation and angle
The orientation and inclination (angle) of the roof can affect the performance of your solar installation and, in turn, the number of photovoltaic panels you need.
In Spain, the recommended orientation of the solar panels is south-facing and with an inclination of 25-35º.
Even so, when south orientation isn’t possible, and you can achieve a southeast or southwest orientation, then you will only lose around 1% to 4%, which is quite manageable.
Regarding the inclination (or angle), this is also relative. As the panels have their own mountings, it really isn’t worth altering the aesthetics of the house just to gain around 1-2% in energy production.
- Power and efficiency of photovoltaic panels
The type of solar panels, as well as their performance and potential energy, are important when calculating how many solar panels a house needs.
The potential energy of the solar panels is how much electricity they can generate. This is specified in the product data sheet. Currently, there are 15W, 80W, 100W, 150W, 250W, 260W, 300W and 320W photovoltaic panels.
A typical solar panel can provide between 380W and 470W, although it is becoming increasingly common to see domestic solar panels with a higher output (500W).
However, we should bear in mind that this figure refers to the potential energy of the solar panel under optimal conditions, which is not the same in all areas and at all times.
As regards the type of panel, polycrystalline and monocrystalline panels are usually used in home solar self-consumption systems.
You should bear in mind that the higher quality systems are slightly more expensive, but they are also better at harnessing the sun’s energy, and, because of this, they are able to generate more electricity. In this regard, the better and more powerful the solar panels are, the fewer you will need.
However, panels with a performance of more than 500Wp/h are considerably bigger, and so we advise going to see a specialist technician who will customize the installation to the size of your roof, as well as taking into account other factors regarding your home.
Before choosing your solar panels, we recommend that you choose experienced manufacturers with a good reputation in the sector, and seek advice from specialised companies such as MyGreenHouse.
- Hours of production vs. hours of energy consumption
The last aspect we need to take into account when calculating how many solar panels a house needs are the times of the day we consume most electricity.
For example, if you use most electricity in the middle of the day, when the sun is strongest, then you will make the most of the solar installation.
However, if you use more energy at other times, you will have to consider the option of installing more panels to generate surplus energy and store it in an electric accumulator or battery for use at another time.
Do you need any more information?
Installing solar panels is an important decision that will bring you many long-term benefits, but it also requires a considerable initial investment. For this reason, you should seek expert advice to help you design the most suitable installation for your home, according to its orientation, its geographical location, and the space you have available on the roof or terrace. Call us and ask for a free assessment!