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Calculate how many Solar Panels are needed

Solar energy reached a great development in recent years, if you are interested in buying solar panels for your home to know how many solar panels do I need for a house?

Calculate how many Solar Panels are needed

Calculating  how many solar panels you need for your self-consumption installation in a house  is relatively simple. However, although we will give you a series of tips so that you can make an estimate, we recommend asking  a professional for a  quote for solar panels for a single-family home .

You should consider that although, roughly, you can calculate how many solar panels you need for your house, it is important that later it is a professional who analyzes in detail the consumption of the house, the orientation, if there are shadows … a series of details which are fundamental.

Did you know that if there are  shadows on your roof, and they affect your solar panels , it can mean that their production drops 100% even if they only have a 10% shadow?

This occurs with the vast majority of conventional solar panels,  except with SunPower panels . But they are the kind of details that, if you’re not a professional, you can overlook and be a mess.

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For this reason, we always insist that the installation of your solar panels must be done and calculated by a professional.

Remember that we can put you  in contact with professional installers in your area without obligation of any kind .

And one more fact to take into account before continuing : It always requires photovoltaic panels with a 25-year product guarantee and also a 25-year production guarantee (power or performance). Don’t you know why? Then read this article on ” the fine print of the solar panel warranty .”


This is one of the most frequent questions when we want to put solar panels in a house. How many solar panels do I need? For this, it depends on several factors that we are going to detail in order to make an approximate preliminary calculation, although it must always be done later by a professional and / or installer.

How much will you be able to save?

Following as a guideline with the case of a 3kW installation. Your savings will come based on the energy produced by your solar panels and the energy consumption in your home. In Spain, depending on the region, the production of 3kW in solar panels would be:

  • For Zone with about 1,300-1,400 HSP approx : A production of about 4,200 kWh / year.
  • For  Zone with about 1,500-1,600 HSP approx : A production of about 4,800 kWh / year.
  • For  Zone with about 1,700-1,800 HSP approx : A production of about 5,400 kWh / year.

What do you need to estimate the panels you need?

For this, it is better to have it done by a professional, however, to be able to make a basic idea, we leave you the following guide so that you can make an approximate calculation of how many photovoltaic panels you need for your home.

Basic guide to make the preliminary calculation:

Before knowing  how many solar panels are necessary for a house , there are criteria that you must take into account to calculate the solar panels you need for your house:

  • The energy consumption of your home : It is the first aspect that you should consult. Without that information it is like going blind. You should look at the  kWh  you consume, and if possible, even discriminate that consumption during the hours that  solar energy is  available (that is, during the day).
  • The available surface to place the solar panels on your roof : Fundamental too. It is of little use to have correctly calculated the number of panels you need, if later we do not have enough space on the roof. There are usually no space problems, but if you have shadows … that can limit the power to install.
  • The orientation of your roof:  Another critical factor is the  orientation and inclination of the solar panels . The more space available facing South (South-East, South-West), the better. The more oriented to the North … the less you will be able to take advantage of it.

Let us now look at these criteria points in a little more detail now.

Data to take into account about the solar panels to install:

  • Total power:  It results from multiplying the number of solar panels by their power. That is, if you need to know how many solar panels you need for 10kW of power, and you use 330W panels, you will need 30 or 31 panels.
  • Orientation and tilt : May affect performance. The ideal is always orientation as SOUTH as possible and with an inclination around 35º. However, it is also to find a balance point with integration, especially in homes where, sometimes, it is not worth breaking the aesthetics to gain 2-3% of production.
  • Technology:  If you are looking for maximum performance, you should know  that the solar panel you need for a house  will always be  monocrystalline . The other technologies are cheaper, but have worse performance and also worse aesthetics for integration into the roof of your home.

Energy consumption of your home:

As we say, the ideal is to know the energy consumption kWh / day that your house has. But it is important that from that energy consumption, separate what is done during sunny hours and what is done during hours without sun.

The reason is logical, you should think that to calculate the solar panels you need for your home, you always have to think about it when they are going to receive  solar radiation . For this, a consumption meter is generally used  , which is what your solar panel installer will use   to analyze the consumption profile of your home and design your installation correctly.

Solar panels for a home: an example so you can apply it

Suppose you have a consumption, in sunny hours, of 8,000kWh / year.

And we are going to think that in your geographical area, let’s say Madrid (Spain) you have Peak Sun Hours of 1,600 on an annual average. The Peak Sun Hours are the sum of annual hours in which the solar panels are calculated to be receiving 1000W / m2, that is, they will work at maximum theoretical power.

So, you can make the  approximate calculation of solar panels that you need  like this:

Consumption of the home in sunny hours: 8,000kWh / year

Peak Sun Hours in Madrid (Map): 1,600HSP

Total power of solar panels needed : (Home Consumption) / HSP = 5,000Watt.

That is, you will need a total power of 5,000 watts of solar panels. If, for example, you have  320W solar panels , the bill is easy:

(Total power of solar panels) / Unitary power of the plate = 15.62 solar panels -> 15 or 16 solar panels would be the final count.

How many kWh does a solar panel produce?

If you want to see it in another way, you can also calculate  how many  kWh  a solar panel produces , in our case:

320W * 1,600HSP = 512kwh / year will produce 1 320W solar panel in that area of ​​Madrid.

Available space on the roof of your home:

Once you know how many solar panels you will need, it is time to see how much space you will need for the  photovoltaic installation  and if your roof has enough space for it.

One of the tips that we usually give to installers who work with us is that for solar panel installations for houses, it is better to use medium-sized panels (1.7 x 1.0 m) and if possible black in color. The size is to make it easier to install and adapt to the roof. And the black color is for a purely aesthetic issue.

If you are interested, you can take a look at the summary on  solar panel prices for houses  to get an approximate idea.

How many solar panels do I need for a house?

There is no doubt that if you are going to put solar panels on the roof of your house, it is preferable that it be something pleasant to look at, rather than a “botch” that you will see every day.

How many solar panels do I need for a house of 200m2 and 100m2?

More than the surface of your house, what you need to know is the consumption that you have in your house. A regular house that has constant consumption is not the same as calculating how many panels you need for a country house, where consumption is occasional by season. Once you have that consumption data, you will need to calculate the number of plates and the space to install them.

To calculate the space you need for your solar panels, it is simple. You should ask yourself these questions:

  • What solar panel am I going to install? . You must select the solar panel that you see that gives you a good guarantee, quality, performance … and when you do, look at the  unit size of the plate  in question.
  • What space do I have on the roof? . If you do not have shadows, and the roof has a good slope and orientation, you must measure what space you can dedicate to the solar panels.

An example of the surface you may need

Continuing with the previous example, with 16 SunPower P19-320 solar panels for example:

Plate area: 1,690 mm x 998 mm -> 1.68 m2

Area you need on the roof : (Panel surface) x (Number of Panels) = 27m2 approx.

That would be the “rough” surface. Then it will be up to your installer to see if it is going to be installed in 2 rows, in 3, if horizontally, vertically … etc.

If you are a photovoltaic installer and you need a  price for photovoltaic panels  or any other element for your photovoltaic project, please contact us.

As you can see, calculating the solar panels you need for a home is very simple, at least roughly. But you should always rely on a professional installer to advise you and carry out the installation and calculation work.


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