How to calculate the size of a domestic solar energy installation

The installation of photovoltaic systems demands knowledge of sizes of batteries and solar panels, here we will analyze how to calculate the size of a domestic solar energy installation

If you are thinking about moving to solar energy, you will notice it in your bills and in your contribution towards a more sustainable and responsible energy model.

However, before getting down to work with your home installation, you should do some calculations to determine how many panels you will need and what size, which has a lot to do with your daily consumption.

How to calculate the size of a domestic solar energy installation

Budget and available space will be two fundamental aspects  that, from the outset, will impact the size of your installation. If the roof or any other area in which you plan to install the panels is not very large, the amount of energy that you can generate will be limited or conditioned to a greater investment in panels than high performance.

If the pocket tightens, then adapt the system to your needs as much as possible, it will be a maximum. To determine the size that best suits what you are looking for, you will have to answer the following questions.

How much energy do I need?

Before making any decision it is important to know  how much energy you consume per day  to adjust the domestic installation of solar energy to your real needs. To guide you, you can divide the monthly consumption that appears on your invoice between the days of the month and, thus, you will obtain your average daily consumption.

However, to refine this data, it is worth taking into account another key aspect: that the efficiency of the panels is not invariable. The clouds, the night or any shadow will impact. Therefore,  the ideal is that you add 25% more to daily consumption .

What is the sun exposure of the house?

The question is also important, since the dimensions of the installation (and the type of panel you choose) will not be the same if you reside in an area with short days and predominance of clouds, than if you do it in a very sunny area .

Therefore,  divide your daily energy consumption between hours of sun exposure of your home  per day. The result, expressed in kWh, can be passed to watts by multiplying it by 1,000.

There are applications that can help you with this calculation, such as  Google’s Sunroof .


How many solar panels do I need?

The truth is that it depends. Give a closed answer to this question is complicated, since the  types of solar panels  available in the market are so varied that part of the key will be the model you choose and their levels of performance.

However, simply to guide you, you can divide the energy consumption per hour of your house between the solar panel voltage and, with this, you can make an estimate of the number of plates you might need. If you perform the calculation with high and low voltage options you will have more possibilities to value.

How much do I want to pay per square meter of panel?

The budget charges, once again, prominence and is that, undoubtedly, will be an essential element to determine the size of the installation and, also, the type of panel by which it is chosen. There are many factors that impact on the price, for example opt for polycrystalline or monocrystalline cells. In any case,  mid-range systems can cost 20 euros per square meter up .

Posing all these questions will allow you to fine tune when choosing the installation that fits what you need for your home. Perform this previous work and track the market supply of panels will occupy some time but it will be worth it because there are many  r EASONS to install solar panels. It is estimated that a panel can produce at least 9 kWh of energy per square meter per year. With this, calculate how much clean energy you can get and how much it is going to be in terms of savings on the energy bill.

An improvement, and step towards self-sufficiency, for your domestic solar installation would be to provide it with an energy storage system. Here we help you to guess the size of the batteries in your home solar system.

First step: How many amps per hour do I need?

To answer this basic question, you will need to follow the process described below:

  1. Size of the inverter.

To determine the size that your investor will need, the first will be to  calculate the maximum consumption peak . A formula to know will be to add the watts of all the equipment you have in your home, from microwaves, to computers or a simple light bulb. The result will determine the size of the inverter.

  1. Daily energy consumption.

Something that you can not neglect will be to find out  how long a day you have activated each of the teams . Once you determine it, multiply the watts of each device by the number of hours of use and then add all the subtotals. As this calculation will not take efficiency losses into account, multiply the result you have obtained by 1’5 .

  1. Days of autonomy.

At this point it will be necessary to decide what autonomy you are looking for. Thus, you will have to  determine for how many days you want the battery to be able to supply you with energy . Typically, autonomy will go from two to five days.

  1. Storage capacity.

The last step will be to calculate the ampere capacity per hour of the battery. To do this, multiply the total daily watts per hour for the days of autonomy that you have determined. Subsequently, multiply the result by two, which will be expressed in kWh, so you will have to pass it to ampere hours. To do this, divide it by the battery voltage.

How to calculate the size of a domestic solar energy installation


Second step: Beware of overloading your batteries.

Once you have determined the capacity you want to store and the location of your panels, it will be time to decide which load controller to use. Compared to the previous one, this step will be relatively simple since basically you will have to  divide the energy that your solar panels capture between the voltage of the batteries . The result, expressed in amps, will clarify the exact type of driver you will need.

Third step: Wiring the system.

Before buying the batteries you will have to keep in mind how many you will need. In this respect, wiring can play an essential role. Thus, the objective of this third step will be to find the configuration that produces the ampere hours and the voltage that you have calculated in previous phases.

There are  two methods for wiring: in parallel or in series , option in which the voltage of the batteries is added. On the other hand, in a parallel wiring, what is added is the current. These two systems can be combined to produce exactly the voltage and amps per hour that you want. This aspect will be more important than it seems, because the success of the formula you have applied to determine the energy you need will depend on it.

With this last step the operation is completed. So, now you can continue to shape your home computer with the guarantee that, despite being out of the network, your system will provide all the energy you need for your home.

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