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When do renewable energies are interesting?

A lot of people hope to save up on their invoices by installing solar panels or wind turbine at home. But renewable energies are rarely competitive against national distribution of energy.

Renewable energy are useful when we are in the bush and have no other choice than a generator.

For installation in town, there are different solutions to avoid the power cut often present on the African continent, and be protected against sub-tension or surge.

The first thing people think, is that they are going to economize on their bill thanks to solar panels or wind turbine. Which is rarely the case, an installation is profitable only when you are in isolated site and need the use of a generator, which is very expensive on an everyday use and maintenance.

You must know that solar or wind installation are not useful when it is possible to get the JIRAMA or grid utility because costs of renewable are simply too expensive, even though the prices are going down. However it is possible to install a power cut system.

How to size your installation?

Here are the following steps to get the good size for installation:

  1. Get the best estimation of your energy consumption
  2. Find the number of sunshine hours of your future installation site
  3. Calculate the power of solar panels you will need
  4. Estimate the size of the converter
  5. Estimate the size of battery bank

How to estimate its own energy consumption ?

First step for any solar projects is to quantify the energy that you need. From this quantity you will know the power of the solar panels or wind turbine you need.

Links to free energy estimation tabular form
With Microsoft Office Excel
With Open Office Calc
With PDF Reader

This is easy to calculate, you just have to put all your electrical devices and the using time per day. The energy used by appliance is the multiplication of its potency by its time of functioning per day so you will get a quantity in kWh/day (kilo Watt hour per day). You have to be very precise to avoid an over or under dimension of your installation.

Here is an example:

2 bulbs of 15 Watt used 3hours par day

  • 2 bulbs x 15 Watt x 3h/day = 90Wh/day

1 TV of 50 Watt used 4h/day

  • 1 TV x 50 Watt x 4h/day = 200Wh/day

The total consumption per day for those two devices is 290Wh/day (90+200)

From this example you just have to add all your equipment consumption and it's done!

If you have apparatus connected to direct current, make a different tabular form because the mode of counting is not the same in direct current and alternating current (AC 220V type, JIRAMA, EDF or any utility grid)

Now that you have your energy consumption per day, you can think about energy conservation. Indeed, with solar or wind system, the energy is not limitless unlike the JIRAMA.

And the more you will reduce your consumption, the more your investment will be low.

And here is a list of very energy- intensive devices that you should proscribe:

  • Air-conditioning
  • Ovens, electrical stoves
  • Electrical heating, electrical water-heater
  • All that contains a resistance in general, flat irons…

Less heavy on energy but still…

  • Any apparatus with motor in general, fridges, pumps, suppressers, household applianceand vacuum cleaners.

So, once we have started to evaluate energy quantity needed, we understand quickly the necessity, and in some cases the obligation, to select electrical device with low need of energy.

Except with unlimited budget!

Luckily as you can see, lots of those devices are not necessary or can be replaced by other energy such as gas for cooking, or the sun for hot water.

So, to reduce energy quantity that we use in a day, there are many strategies:

  • Choose simple devices, for example a chandelier with 12 bulbs, even economical one, will always use more energy than 1 bulb.
  • For lightening in general, do not use lampshade that stops the luminosity, and put your lamps where you need them most.
  • Prefer the "thrifty" receivers, of class A on the tab energy, economic bulbs, or Led for illumination.
  • If you are on the beginning of your project and do not have apparatus, try to buy them with direct current, such as for lightening you can use 12 Volts.

On this tab, the « A » show the more economic until the highest energy-intensive.


The goal is to get the perfect match between consumption and production.

Now you can, with the help of your balance energy sheet, calculate energy consumed per day and so finish sizing your installation.


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