Understanding the electricity bill

Many people are paying monthly invoice by using electricity as a source of energy without knowledge of who exactly is each concept, therefore I want to create a small Guide to better understand what and how to save.

Term of power

The first concept to understand is the term of power, is represented by the contracted power multiplied by the number of days and the price. The power is defined as the power between the time and the companies charge for the maximum power you hire. Let’s take an analogy with cars, here would be as if you monthly charged by the power which has your car independently then you use it or not, if contracts power to go to 200 Km/h, then the maximum that you use is 50 Km/h are paying more respect what you use, if you reduced the power at 50 km/h and one day like to run more won’t be able to.

This part does not rise excessively an invoice price but it is advisable to adjust it to the consumer and the needs of each property. To save this part is very important to know what you use, it is not for nothing advisable to have lights and electrical appliances create an Excel table and perform a calculation simple, because sometimes appliances escape us or many even have a higher energy consumption than we think. For example halogen transformers can consume 5w and the own halogen 50w if we simply count the luminaires and multiply by 50w are estimating a 10% less of what they consume.

The best is to look at the consumption with a network Analyzer, but for a home, a good approximation with a clamp may be and by turning and machines, for example the washing machine and the dishwasher may consume much at a point in time, taken into account but never put them at the same time. It same them lights, never have all the House turned on, or not should… but it depends on the needs of each House.

Consumed power

This is the part really important of it invoice is what consume, in the example of the car would be the gasoline as more quickly are going more consumed (not will have in has them marches in this example), as more devices turn more consume, simple and simple. This part can be saved in two ways mainly: using the installation with some intelligence or using more efficient technologies.

The first part is simple, when not are in a site turn off the light, certain devices have consumption even off (consumption ghosts) as them electronic, not using heaters electric to get to temperatures exaggerated (above 23 °). The second part can simply be found B energy efficiency labels, A, A + or A ++ and similar, these indicate one greater than 50% savings, you have that examine whether the investment is really interesting for every installation, if we have a light bulb in a place we go once a month is not necessary a change to instant LED but if in the lights that are lit more than ten hours.

Energy efficiency label
Energy efficiency label

Consumption is represented on the invoice as the energy consumed in Kw/h multiplied by the price. Here we have two case, some houses that have the same price for 24 h and time discrimination that has three periods: Tip, plain and Valley.

Periods of time Duration
Tip 4 hours/day
Plain 12 hours/day
Valley 8 hours / day

Dwellings there is double time discrimination hours tip (10 h) and valle (14 h), less than 10kw.

Considered hour tip, plain and Valley, in each of the areas, as follows:

Area Winter Summer
Tip Plain Valley Tip Plain Valley
Peninsula 18-22 h. 8-18 h.
22-24 h.
0 – 8 h. 11-15 h. 8-11 h.
15 – 24 h.
0 – 8 h.
Balearic Islands 18-22 h. 8-18 h.
22-24 h.
0 – 8 h. 18 – 22 h. 8-18 h.
22 – 24 h.
0 – 8 h.
Canary Islands 18-22 h. 8-18 h.
22-24 h.
0 – 8 h. 11-15 h. 8-11 h.
15-24 h.
0 – 8 h.
Ceuta and Melilla 19-23 h. 0-1 h.
9-19 h
23 – 24 h.
1-9 h. 11-15 h. 9 – 11 a.m.
15 – 24 h.
0 – 1 h.
1-9 h.

To check the prices of each part, you can visit chcenergia.es where to update them monthly. This would be another way of saving, use the machines in the cheapest periods.


In all three phase installations (almost none in homes) the companies sanctioned by the use of the reactive, surely if we are not technical nobody knows which is the reactive. I soil express it as a current that enters and leaves by the cable but that not is consumes, if it compared with a highway is as if entered in a toll and us spent three days inside until left giving turns and wearing them roads but to the exit only us charge the output from the input, however have “enjoyed” of it driving in such Highway We should pay more. In the electricity passes with facilities inefficient that must be updated, the companies us sanction because overwhelm their lines without consume by what created a prejudice if all have a high reactive. The sanction depends on of an equation trigonometric in which does not want to enter in details, but to more reactive depending on the consumption of energy more pay. The solution to save here is install battery of capacitors with the study corresponding to each consumption, or replace the old.

Rental counter and taxes on electricity

The company us rent the apparatus of measurement, here there is a strong debate on until point the rent must be paid by the user or by the Distributor, this is a cost fixed monthly. On the other hand also there is a charge for the use of electricity, which depends on the sum of the contracted power and energy. I.e., the total of the invoice less the rental counter, since that price is not consuming energy.

Examples invoices

Below are two invoices from the two largest companies one for housing and the other three-phase.

Three-phase endesa invoice
Three-phase endesa invoice

Bill single-phase Iberdrola
Bill single-phase Iberdrola

For any questions you can leave a comment on the website or email us without commitment. If you want a service audit energy we can make a budget.

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