How to calculate the electrical power you need in your home


How to calculate the electrical power you need in your home

How to calculate the electrical power you need in your home

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Often doubts arise as to the power contracted. In this article we will advise you on the most suitable power according to your case. Through an estimate of the contracted power that you can do yourself.

The calculation will be indicative, you should always go to an expert or your marketer in order to conduct a more detailed study.

The method of calculating the appropriate power is to add the kW needed to operate each appliance of those used at home. Which will be divided by groups since not all are connected at the same time.

The described powers are normalized powers, which are a mere estimate since the Royal Decree-Law 15/2018 of urgent measures for the energy transition and the protection of consumers modified the standardized powers. Allowing to contract the power in sections of 0.1 Kw, thus disappearing the sections of normalized powers that limited the hiring to these values.

In the first place, we show you some generic examples of the contracted power according to the type of housing:

Study   Power ≥ 2,3 kW
 Small apartment  Power  ≥ 3,45 kW
Medium/large apartment  Power  ≥ 4,6 kW
Large house  Power  ≥ 6 kW
Contracted power calculation

The estimated calculation of the contracted power can be obtained with the sum of the power of the highest consumption and power appliances. Once added, you must add a margin of 1 kW of lighting and small appliances.

In the same way, and taking into account that the appliances of greater power will not be used at the same time. Divide the aforementioned sum by 3. The resulting figure must always be higher than the maximum power appliance since otherwise it could not be used.

Once you get the recommended contracted power, it is important that you consult with an expert or your marketer in order not to rush wrongly.

Average table of the power of each appliance with greater power

Appliances W Power
Electric heating 1.000 - 2.500  1 - 2,25 kW
 Washing machine 1.500 - 2.200 1,5 - 2,2 kW
Dishwasher 1.500 - 2.200 1,5 - 2,2 kW
Oven 1.200 - 2.200 1,2 - 2,2 kW
Air conditioning  900 - 2.000 0,9 - 2 kW
Microwave 150 - 1.500 0,15 - 1,5 kW
Television 150  -   400 0,15 - 0,4 kW
Refrigerator 250  -   350   0,25 - 0,35 kW
Vacuum cleaner 950 - 1.500 0,95 - 1,5 kW
Toaster  550 - 1.000 0,55 - 1 kW
Ceramic hob  900 - 2.000 0,9 - 2 kW

According to the type of household, as well as the members of it, it is estimated that the recommended contracted power recommended is.

  1 or 2 people 3 or 4 people 5 or more people
Without heating; Vitroceramic and Air conditioning 3,45 kW 4,6 kW 5,75 kW
 With Heating; Vitroceramic and Air Conditioning 4,6 kW 5,75 kW 6,9 kW



A couple with a child want to move to a medium apartment, which has the following electrometric:

  • Electric heating
  • Air conditioner
  • Washing machine
  • Oven
  • Refrigerator
  • TV
  • Microwave oven
  • Toaster

Taking into account the data provided:

  1. Being an apartment mediating, it will be a contracted power equal to or greater than 4.6 kW.
  2. There are 3 people and your home has electric heating and air conditioning, being a recommended contracted power of 5.75 kW.

Therefore, we will perform the manual calculation in reference to the kW of each electronics.

Electric heating  2,5 kW
Air conditioning  2 kW
Washing machine  2,2 kW
Oven  2,2 kW
Refrigerator  0,35 kW
Refrigerator  0,4 kW
Toaster  1,5 kW
Tostadora  1 kW
Total 12,5 kW

Then we will add 1 kW for lighting and small appliances.

12,5 kW + 1 kW = 13,5 kW

Finally, we will divide the figure by three, since not all appliances work simultaneously.

13,5 kW / 3 = 4,5 kW

In conclusion, the result of the operation is 4.5 kW. Taking into account that Royal Decree-Law 15/2018 modified the normalized powers, it is allowed to contract the power in 0.1 Kw sections, thus eliminating the sections of standardized powers that limited the contracting to these values. Therefore, you can make contracted power modification in any multiple of 0.1.

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