If you want to charge an electric car at home, you should know that ...

Before making the decision to charge an electric car in our garage, we have to pay for some details about the electricity supply and the cost that it will have. For that you have to do some numbers first.

Electric cars can be charged anywhere, but there are some small ones that have to be taken into account. The faster we want the load to be, the more we go deeper into technical issues.

If we have a detached house with a private garage, we will surely have a 10 ampere outlet, which would give a maximum of 2.3 kW of power. Before continuing, it is worth remembering a basic formula in relation to electricity:

           P = I x V, or power equal to the product of the current (in amps) for the voltage

For example, with 16 amps and 230 volts we get 3,680 watts, or 3.68 kilowatts (kW). The speed at which   an electric car is charged depends on the load power, and this in turn of the intensity, since the voltage is "constant".

If we have a power of 3.68 kW, it means that every hour can recharge a little less than 3.68 kWh, since you have to consider them in the process. For every full hour, multiply. In 10 hours we will have loaded something less than 36.8 kWh. Simple, right?

Cars can have a small charger for occasional use, or a specific connector for charging points designed for that purpose. In some cases, the occasional charger is sold separately and is not included in the equipment.

The occasional charger is not as fast as the specific charger, and it can work really slowly. For example, if it works at 6 amps, we would need 12 hours to reach 16 kWh. If we talk about Nissan Leaf with the largest batteries (30 kWh), in those 12 hours we would not recharge even half, but would give for something more than 100 kilometers of autonomy.

The ideal is to have a specific recharge point, with 16 amps and 3.68 kW of power

Depending on the installation, there will be more or less work and modifications to the electrical circuit. The thickness of the cables, for example, is a factor to be taken into account. The regulation that regulates all this is called TC-BT-52, of the Low Voltage Electrotechnical Regulation, approved last year. All facilities must be for each qualified person, it is not something that can be used by IKEA.

You can install a charging point in the collective parking space, informing the community president, how Law 19/2009 defines, measures to promote and streamline the rental and energy efficiency of buildings. If necessary, approval is also required from the community of owners.

Depending on the case of each one, it can be installed with a separate contract or a line will be derived from the main meter to the loader. It is advisable to consult a qualified electrician, because this type of installation can only be done by them. The cost depends on what needs to be done in each case

On the margin, it is necessary to consider the cost of the recharge point itself, depending on its power, security measures and types of connectors. The most basic ones have Schuko (or type 2) connectors and others the Yazaki (or type 1). A guide price is between 500 and 1,500 euros.

Contract costs and electricity

Few people have read in depth the electricity bill, and it is convenient to do so. In my case I have contracted 3.45 kW with time discrimination, in the most advantageous rate I pay every kWh of consumption to 0.067189 euros. Each kilowatt of available power costs me 3,503,605 euros. For 3.45 kW of power, I pay 12.09 euros per month, consumption and electric taxes go separately. That is the fixed term.

With this power I can not recharge at 16 amps, would jump the differential magnetothermic (or "the leads") to exceed the 3.45 kW. At 10 amps yes could recharge, 2.3 kW, if not simultaneous with another kilowatt of household appliances or whatever. Therefore, to charge 16 amps requires more power contracted. A single-family home usually has more power, 16 amps are not a problem.

An electric car consumes about 12-14 kWh per 100 km

Without the hourly discrimination, the 30 kWh of a Nissan Leaf could recharge them with 3.82 euros, without considering losses. With nightly rate it would go down to 2 euros. There is an even lower rate, the supervalle, to which I have not accepted. That is the variable term, what we pay for consumption.

Returning to the example of 10 amps, to get energy to do 100 kilometers, on average (13 kWh), I would need about six hours and it would cost me 0.87 euros. Without time discrimination, it would not reach 2 euros. That cost is unattainable for any car with a thermal engine, even if it uses gas.

Hence the importance of seeing the bill, to give an estimate of how much it would cost to recharge. If a second contract is needed, the fixed term or the contracted power would have to be paid separately.

Seen the seen, one understands that it is not viable to place a quick recharge point at home (requires 40 kW of power) unless you have a very healthy current account. It would be 140 euros per month only of contracted power, even if the car was not loaded even once.