The number of solar panels that any photovoltaic installation will need will depend on the energy consumption, which can vary between low, medium and high.
How to calculate solar panels?
Calculating the number of solar panels is one of the most important procedures in the implementation of a photovoltaic installation. This step is technically known as sizing and is carried out taking into account the amount of energy consumed (measured in kWh) during a year.
The following table shows how the number of solar panels required can be calculated according to consumption. Specifically, an electricity bill is used to find out the annual consumption in kWh, quantify the number of solar panels that will be needed and forecast their installation cost.
Solar panels calculation
| Type of consumption | Electricity bill month | Consumption kWh/year | No. of solar panels | Price of installation |
|---|---|---|---|---|
| Under | Less than 50 | 2,400 kWh/year | Less than 3 panels | Around € 2,500 |
| Low – medium | 50 – 100 € | 3,600 kWh/year | 3 – 6 panels | From 3.300 € |
| Medium | 100 – 150 € | 6,000 kWh/year | 6 – 9 panels | Starting at 4.800 € |
| Medium – high | 150 – 200 € | 8,400 kWh/year | 9 – 12 panels | From 6.300 € |
| High | 200 – 250 € | 10,800 kWh/year | 12 – 14 panels | From 7.500 € |
| Very high | More than 250 € | 12,001 kWh/year | More than 14 panels | From 9.100 € |
Approximate figures
In this way, and following this table, any person can know how many solar panels he/she will need to be self-sufficient. All you need to do is
- Have access to the last electricity bill you received.
- Place yourself in the table, in the price range that corresponds to your case.
- Take a good look at the other consumptions that you have near your cell, because the final calculation may vary.
Solar panels calculator
Another option, also free and online to identify the number of solar panels that will be needed, is to use a solar panels calculator. This is a very useful tool, which is made available to any user by the installation companies, and which allows you to quantify the number of solar panels and the price of their installation.
These solar panel calculators work in the same way as a form. Through a question-answer system, they are able to identify the user’s energy needs. In such a way that, at the end of the questionnaire, they can issue an indicative budget.
In some cases, this final document also provides an estimate of savings and a financed installation price. In fact, this is the case of the online solar panel calculator that BlueSolarPanels has set up.
Through it, a user, whether the owner of a house, a commercial premise or belonging to a community of neighbors, can get a general idea of the number of solar panels that will be needed.
Although a multitude of similar tools can be found online, most solar panel calculators usually ask the same questions to the user, as these are necessary to provide any kind of indicative installation budget. Some of the most common ones are:
- Asking for the type of building where the panels are going to be.
- Asking for the address or zip code
- Knowing the energy consumption: through the electricity bill or the CUPS number.
- Inquire about the type of roof on the property
- Need some personal information such as email or telephone, to detail the information provided.
Why use a solar panels calculator before installing? Before installing it is highly recommended to use a solar panels calculator. This tool allows users to get an insight into photovoltaic energy and learn first-hand about key aspects to make the decision to switch to solar self-consumption.
How many solar panels do I need for a house?
To illustrate how to calculate the number of solar panels based on energy consumption, let’s see how many solar panels would be necessary for a house. Specifically, for 2 types of houses:
- The first dwelling is a rural house, of sporadic use, which has a low energy consumption.
- The second dwelling is a residential house, which has a high energy consumption.
We are going to observe, comparing both cases, how the number of solar panels needed increases based on a higher or lower use of household appliances.
Number of solar panels as a function of plugged-in items
| Elements plugged into the grid | Number of solar panels you will need |
|---|---|
|
You will need 4 solar panels |
|
12 solar panels |
Also, apart from energy consumption, other factors can be used to calculate how many solar panels a house needs. Mainly, there are 2:
- The surface area of the house (m2)
- The number of people living in the house
How many solar panels do I need for a house of a specific m2?
How many solar panels do I need for a 200 m2 house?
The number of solar panels needed for a house of 200 m2 is between 8 and 12 solar panels. This is a large property, which will need several panels to supply the lighting and other domestic energy it uses.
How many solar panels does a 100 m2 house need?
Typically, the number of solar panels being installed on houses with a surface area of 100 m2 is between 4 and 8.
How much does a solar panel produce per m2?
A 460 W solar panel can produce about 350 kWh per m2 per year.
However, the energy production of the solar panel per m2 will depend on the power, the material, the size and the other characteristics that make up the price of solar panels.
Finally, another element that could be taken into account to calculate how many solar panels a house needs is to analyze the number of cohabitants. Normally, a house with a large family tends to need more energy than a house with a married couple. Even if both have the same square meters.
Calculation of solar panels according to the number of cohabitants
| Number of cohabitants | Number of solar panels | Price of the installation |
|---|---|---|
| 2 persons | 3 solar panels | 3.300 € |
| 6 persons | 9 – 12 solar panels | 6.300 € |
| 4 persons | 6 persons | 9.100 € |
Also, and within the sizing process, users are often interested in the number of solar panels needed to be able to consume a number of kilowatt hours per year, or the number of solar panels needed for their installation to have a certain power (Wp).
Here are the most frequently asked questions on this subject.
How many solar panels do I need according to the Wp power?
How many solar panels do I need to generate 5 kw?
With a good orientation and inclination, you would need 8 solar panels of 460 Wp to generate 5,000 kWh/year of consumption.
However, if you want to have a photovoltaic installation that reaches 5 Wp, you would need 11 solar panels of 460 Wp.
How many solar panels do I need for 4000w?
Users who are interested in having a solar panel installation to consume 4000 kWh/year will need 6 solar panels of 460 Wp.
But if they want to have an output of 4000 Wp they will need 9 solar panels.
How many solar panels do I need for 3000w?
With a good orientation and inclination, 4 solar panels of 460 Wp would be needed to generate 3,000 kWh/year.
However, in the case of a self-consumption installation with a power of 3000 Wp, 7 solar panels will be necessary.
How many solar panels do I need for 20,000w?
35 460 Wp solar panels are needed to generate 20,000 kWh/year.
And if you want to have an installation of solar panels that can reach 20000 Wp, 43 solar panels would be needed.
How many solar panels do I need for 2000w?
With a good orientation and inclination, 3 solar panels of 460 Wp would be needed to generate 2000 kWh/year of consumption.
On the other hand, to have an installation that reaches 2000 Wp, 5 solar panels would be needed.
How many solar panels do I need for 1500w?
To consume 1500 kWh/year, 2 solar panels are needed. But to have an installation of 1500 Wp, 4 solar panels of 460 Wp would be needed.
How many solar panels do I need to generate 1 kw?
To have a self-consumption installation and to be able to consume 1 kWh/year, 2 solar panels are needed.
However, if what is needed is to have an installation that reaches 1 Wp, 3 solar panels would have to be installed.
Step by step calculation of solar panels
To determine the number of solar panels needed for a self-consumption installation, installation companies use a special formula: the solar panel calculation. This is a complex formula, which should only be carried out by qualified technicians. This is the only way to ensure, as they say in the industry, the correct sizing of the photovoltaic system.
In order to carry out the calculation of solar panels, it is necessary to have a series of technical information:
Data for the calculation of solar panels
User data
- Annual consumption in kWh. You can see it in the electricity bill and multiply it by 12.
- The annual consumption in the example will be 8,400 kWh/year.
- Hours of light per year. It will be necessary to multiply the daily hours of light of the province by the days of the month during a year.
- In the example it will be 2,190 hours (6 hours x 30 days x 12 months).
Technical data of the panel
- Solar panel power. It can be found in the technical data sheet of the product. They are between 300 and 500 Wp.
- In the example the panel potential will be 460 Wp.
- Production loss of the panel. This percentage can be found in the data sheet of each panel.
- In the example it will be 1.15%.
Calculation formula for solar panels
1.- Calculation of daily consumption
- Annual consumption kWh / Light hours h
- Example: 8.400 kwh/year / 2.190 h = 3,8 kw
2.- Introduction of the production loss factor
- Daily consumption kW x Production loss factor %.
- Example: 3,8 kW x 1,15 % = 4,4 kw
3.- Obtaining the number of plates
- Daily production / plate power x 1.000 (to convert to Kilowatts)
- Example: 4,4 / 460, x 1.000 = 9,7
- Answer: 10 solar panels are needed for a consumption of 8,400 kWh.
The calculation of solar panels changes according to the province. In order to make this calculation of solar panels more precise, installers take into account more technical factors such as the production of the panel according to the geographical area. This means that the number of solar panels needed varies from one province to another, even if the building has the same energy consumption.
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