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First, to not enter questions, clarify what is a grid system:

It is an electrical installation (which has wiring and can plug loads) but has no access to grid power.

Any solar kit can be adaptive, but we can always make our own photovoltaic kit. Here are the steps to follow to know what to buy:

     The main thing is to know the energy we need to produce, and when we need it. We answer:
         What are you going to plug?
         How long will it be plugged?

For example: Let's get connected:

     A combi fridge provided
     Two light bulbs of 23W for 4 hours a day
     A medium fluorescent tube 3 hours a day
     A weekly laundry

With these data we can calculate the energy needed to generate each week (at the end of the guide is a standard reference table with powers that can be useful if there are no further data)

Fridge freezer: 220W x 12 hours / day x 7 days / week = 18480 Wh weekly

(they are 12 hours a day instead of 24 hours as refrigerators, when closed van plugging and turning off the compressor to maintain the temperature to tell the thermostat, so about half the time they stand)

Bulbs: 23W x 2 units x 4 hours / day x 7 days / week = 1288 Wh per week

Fluorescent: 18W x 3 hours / day x 7 days / week = 378Wh weekly

Washer: 350W x 1 hour / day x 1 day / week = 350Wh weekly

Ø We know what we need: 20,496 Wh per week or 2928 Wh per day (on average)

     Knowing what we need power panel

Since we want to use the same all year, we know that there will be minimal radiation where we are, it will be in December.

Also, keep in mind two things:

Ø If we have the same year-round production modules must be oriented to the south and raise about 60 °, so that production is maximized in winter, the sun is lower.

Ø If consumption is only in summer, proper inclination will be 30 °.

As a rough reference for the module at 60, on the South half of Spain in December will have 2.8 hours of production or equivalent peak sun. What are the hours the sun would be at 100%.

For example:

For 3000 Wh per day, with 3 sun peaking in December, 1000 W panel would be required.

Always bear in mind that the system has performance loss until it reaches electrical appliances, so you always have to add 25% -30% power. For this example, the power to be installed would be 1300 W.


     Calculate what we need for batteries

To imagine that one day it will not load any of the panels, the energy we need should come from the batteries.

The capacity of the battery in Ah measured for voltage.

A battery of 100Ah and 12V power saves a 1200Wh.

As should never discharge a battery more than 50% (to increase its life) I could calculate as follows:

The necessary equipment for the energy we need in three days corresponding to 50% of its capacity.

For example: If we consume 3000Wh / day. In a set of 12 V need:

3000Wh / day x 3 days x 2 (since we only allow 50% maximum discharge) = 18000Wh

If we do battery system 12V -> 18000Wh / 12V = 1500 Ah


     Calculate what type of investor need

There are 3 types of inverters for grid systems:

· Modified wave inverters: are only valid if we want to "plug" is suitable for modified wave, if only electric pumps and lighting without electronics can be used.

· Sine wave inverters: They are valid for any electric charge, produce a like of any home connected to, often even better mains electric wave.

· Investors Chargers: They perform a dual function, that of a typical investor, plus the ability to charge the batteries from an external source (mains or generator).

It is important to know what voltage we need; must match the voltage of the batteries.

And it's important to know what we need to supply power. There are two ways to calculate it; add all the powers of all the "plug" and if we know that it will not connect at the same time reduce it accordingly.

For example: If you add up the wattage of all the appliances you get to 634W, since at startup appliances may have more power points should not be adjusted too.


     choose Components

Serve as a guide the following scheme:

You must choose:

Ø Photovoltaic module: as many units as needed to complete the necessary power. And the guy we want to install. Generally there are 3 options:

or 12V modules. If our battery system is 12V. 24V if we can put an even number of modules in parallel. They usually come labeled as such, but in case you have doubts you can see on your datasheet.

The maximum power voltage must be between 16 and 20V approx, about 50% higher than the battery voltage.

or 24V modules. If our battery system is 24V. Also usually come labeled as such, but in case of doubt the maximum power voltage-sheet should be between 30 and 40V.

modules or network connection. They are modules other voltages which are only used in isolated facilities with special controllers that adjust the voltage of our battery voltage, these regulators are usually MPPT type, but you need to ensure what configuration of modules can be connected and which not.

The networking modules are usually somewhat cheaper for power and MPPT regulators more expensive than conventional ones. So to install MPPT at least has to be some power, reference, less than 1000W of panels should never install MPPT regulators, and between 1000 and 2000W depend on the price of each module, which is the most variable.

Eg for 1300W, an option with 24V modules would be:

When would require 180W 8: obtaining a power of 1.440W

Ø Solar controller. The controller connects the photovoltaic panels with batteries, carrying its load correctly. They must adapt to the battery voltage, 12V batteries need 12V regulators. In addition, must adjust the maximum intensity of the PV modules to not exceed the maximum allowed by the regulator.

The current controller is what gives it its name. For example, a 12V regulator 30A, will be a suitable for 12V batteries and its intensity is maximum 30A regulator module.

For example: For the module we have chosen must know its intensity:


We know that the maximum intensity of the module in any circumstance is 5.57. As we install 8, the total intensity is 5,57A x 8 modules = 44,56A

We need a minimum 45A regulator.

Option 1: A regulator 45A, as follows:

Option 2: You could also choose to split in two regulatory modules, connecting 4 to each module through two units:

This option is more economical (because regulators are a bit more basic) and allows us to leave the option to extend two modules installation without having to make any changes, because we have so regulation 60A.

Ø Batteries: For small installations are often used monoblock batteries (6, 12 or 24), and for larger installations, it is usually more economical to use glasses of 2V batteries.

For example: It takes 1500 Ah at 12V or 24V 750Ah. One option is:

6 pieces provide the necessary energy that we have calculated.

Ø Inverter: To install a 24V battery and a 634W power required, for example it would:

Sine Inverter.



If only going to have light, to save an investor can install DC luminaries

It may decrease spending on batteries installing more solar panels.

In cases of highly variable consumption are connectable bootable system generators to charge the batteries when they are discharged too. To extending the life of the system and ensure the availability of energy when needed.

A useful and free tool for dimensioning isolated systems can be found at:


Power table reference for common electrical appliances:


40W conventional bulb


60W conventional bulb


Conventional halogen (ox eye)


Fluorescent tube medium


Lightbulb lowest median consumption


Light bulb under large consumption











Washer A ++ (cold)


Dishwasher (50)


fridge freezer


Air conditioning 2500 frigorias


DVD Player




ADSL router


LCD TV 32 "


Plasma TV 42 "


40 LED TV "



PC screen




printer ink


Tower PC





pool Pump


mobile charger