How does Bi-directional Meter work In A Photovoltaic System?

If you have a photovoltaic self-consumption installation with surpluses or think of doing so, you have probably heard of the bidirectional meter. It is an essential device since it will allow the marketer to pay you for your surpluses, and in this way, the price of your electricity bill is reduced.

How does Bi-directional Meter work In A Photovoltaic System

What is a two-way electric meter?

The bi-directional meter is the device responsible for accounting for the energy that flows in a photovoltaic installation in both directions: from the electricity grid to the user (just like any other digital meter) and the energy that the user pours into the network.

This photovoltaic component is essential in self-consumption installations with surpluses. When you do not consume the energy produced by the solar panels and inject it into the electricity grid, the marketer will compensate you for the energy surpluses and will mean significant savings in the price of your bill.

The marketer will use your counter data to compensate you. The distributor provides this data.

When is a two-way meter necessary?

The arrival of the new self-consumption law approved that energy surpluses could be poured into the grid so that users could receive compensation for these surpluses, hence the importance of this type of meter in photovoltaic systems. So when is it really necessary?

The type of photovoltaic self-consumption makes it possible for the marketer you have contracted to compensate you for energy surpluses. The meter shall account for the kWh consumed from the network and those that have been injected into it. It is important to know that the marketing company must approve this device.

On the other hand, you will not need to install batteries to store the excess energy since the energy you pour into the grid will compensate for part of the price of the energy you use on cloudy days, nights, etc. (since it is not possible to produce due to low luminosity). However, only those homes and businesses with installed powers of less than 100 kW can benefit from the modality, with surpluses covered by compensation.

Self-consumption without surpluses: 

The facilities covering this modality have an anti-dumping system that ensures that none of the surplus energy is poured into the electricity grid. This type of self-consumption has the advantage that administrative procedures are scarce.

Self-consumption with surpluses not covered by simplified compensation: 

These are those installations with installed powers greater than 100 kW. In this case, the surpluses will be discharged to the electricity grid, but they will be under the energy sale regime instead of compensation. To do this, they must formalize a representation agreement with a marketer and comply with all legal duties that comprise this economic activity.

There is also the option for surplus installations to sell their energy on the electricity market. However, they must register as generating market subjects and carry out all the necessary procedures to do this.

Isolated installations:

Isolated solar installations are not connected to the electricity grid, so you can’t pour the unconsumed energy. Therefore, it is essential to use photovoltaic batteries to store the energy not consumed and be able to use it later.

How many meters do I need in a self-consumption facility?

In the specific case of self-consumption facilities under simplified compensation, it will be essential to have another meter in the shared self-consumption facilities since it is necessary to measure the energy generated to distribute the participants.

Sometimes, it is necessary to install an additional meter to monitor your photovoltaic system and thus be able to obtain all the detailed data on your energy consumption. This is because the meters are owned by the distributor, and not all provide this information to users to control consumption.


Should I modify the existing counter if I take advantage of simplified compensation?

In the vast majority of cases, no. Today, almost all smart meters are digital, and these, in turn, are bidirectional. Therefore, you will not need to modify the current one. However, in the event that your meter is not digital, it will be necessary to replace it. For this, you will need to contact your distributor.

On the other hand, it may be the case that the programming of the smart meter has been changed so that in addition to recording the energy discharged from the network to the user, it also accounts for the energy surpluses injected into the network.


How much does it cost, and where to buy a two-way counter?

The meter can be acquired as property by the user or, on the contrary, rent it to the distribution company. If the user decides to buy it in property, he is responsible for its correct operation. However, it is much more frequent and advisable to rent it since, in this case, it will only be limited to guaranteeing its custody; the distributor will be in charge of its installation, maintenance, and/or replacement in case there is a breakdown.

The purchase of this device is usually around $100-300 depending on the model. The rental rate is much lower compared to the acquisition. The distribution company will require you to pay through the invoices with a monthly cost of approximately $0.80 – 0.90 , which translates into about 10 euros per year.

In short, it is more expensive to own the meter than to rent it. In addition to the economic cost, the administrative costs of verification.