Lighting: everything you need to know about a plant’s power and energy

As far as lighting is concerned, both in a private context and in a public context, ensuring an electrical system capable of guaranteeing optimal consumption and, consequently, savings on expenses – domestic or business – is determined. To avoid waste, therefore, it can certainly be useful to inquire adequately about the power and energy of a system, be it traditional or photovoltaic.


The  watt  represents the unit of measure of energy  that determines the power of a system. This unit is associated, with multiples and submultiples, with the measurement of the power of the electricity produced or consumed (in the case of electrical appliances).

Speaking of energy, however, we use the watt-hour, the product of power for a time interval; the  kWh,  therefore, expresses the energy consumption of any machine in a given period of time.

When it comes to lighting, finally, another important distinction to keep in mind is that between the watt and the lumen . When it is necessary to identify the extent of consumption of a light bulb, one must look at the power and, therefore, the watt. If, on the other hand, the intensity of the light produced by the bulb itself must be assessed, the lumen must be taken as a reference.


The Observatory on Italian public accounts, in a research carried out in May 2018, highlighted how Italy consumes twice what happens in other European countries in terms of public lighting: we are talking about 6,000 GWh per year and one public expenditure of over 1.5 billion. Think, for example, that this is a figure five times higher than that faced by Germany.

The situation is decidedly more encouraging when looking at the final per capita consumption of electricity, which stands at 2.4 toe : it is one of the lowest values ​​within the European context, as also confirmed by the emissions data of greenhouse gases.

In our country, in fact, there is a percentage decrease of about 20%. This is a real counter-trend compared to what happens in the rest of Europe, where increases continue to be recorded with regard to emissions: just think that Germany has seen the percentage increase by 7%.

This study shows that Italians are paying more attention to electricity consumption than other Europeans. At least in their own homes. But it could be done even better if the use of lamps that have LED technology continues to increase , designed to guarantee low consumption but also sustainability and respect for the environment.


If our home, or company, is powered by a photovoltaic system, the principle for calculating watts and watt hours is identical to the traditional system. Photovoltaic grants on site the energy that would otherwise be supplied by the electricity grid; its  nominal or peak power  is expressed in  kWp  and represents the maximum power that can be delivered in certain standard conditions.

For the calculation of the peak power, predetermined conditions are considered:  25 ° C, sun at 48 ° with the zenith and irradiation of 1000 W / m2 . The nominal power, therefore, represents the maximum theoretical power of a system, which normally instead generates quantities of energy which vary according to the conditions and the sun exposure.


by Abdullah Sam
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