Battery storage and your prosumer grid connection: what actually changes (2026)

If you already have solar panels — or you are planning a system for 2026 — you have probably asked two questions: is a battery worth it, and does storage change anything about the official grid connection? The short version: a battery changes the economics of being a prosumer (prosumator — a consumer who also produces energy, usually from solar panels), it changes a few things in the paperwork, and it changes nothing about the power you are allowed to inject into the grid. Below is the honest picture, from a team that handles the connection side, not the sales side.

One thing first, because the market is full of half-truths: a battery is not mandatory to become a prosumer. You can be connected and certified with a standard grid-tied system and a bidirectional meter, with no storage at all.

How a battery changes the prosumer equation

Solar panels produce most of their energy around midday. Most households consume most of theirs in the morning and in the evening. Without storage, that mismatch is settled through the grid: the midday surplus is injected into the network and offset against your consumption under the quantitative offsetting mechanism, under the ANRE regulations in force.

A battery moves part of that exchange in-house:

• You store the midday surplus instead of injecting it.
• You consume your own energy in the evening, when the panels are no longer producing.
• You inject less into the grid — and you draw less from it.
• Depending on the inverter configuration, some systems can also supply a backup circuit during outages, but only if they are designed for it from the start.

What does not change with a battery

• You still need an official grid connection (racordare) to operate legally as a prosumer.
• You still need the bidirectional meter fitted by the distribution operator.
• The offsetting of injected energy still works under the rules set by ANRE, the energy regulator.

In other words, the battery is an economic optimisation layered on top of the same connection process — not a replacement for it.

Is storage worth it? An honest framing

We do not sell batteries, so we have no incentive to push you either way. A battery makes the most sense when there is a meaningful gap between when you produce and when you consume — and when the energy you would otherwise inject is worth less to you than the energy you avoid buying in the evening. A household that is at home during the day, with flat consumption, gains less; a household that consumes mostly after 18:00 gains more.

If you are still sizing the system, start from your real consumption profile, not from a catalogue. Our guide on connecting solar panels to the grid as a prosumer covers the full process step by step.

What battery storage means for the grid connection

The hybrid system must be declared in the documentation

The connection dossier submitted to Retele Electrice Romania S.A. describes exactly what sits behind the meter: the inverter type and its certificates of conformity, the single-line diagram, the installed power. A hybrid system with storage must be declared as such — the hybrid inverter and the battery appear in the documentation, with their technical data.

This is not bureaucratic pedantry. The operator approves a connection based on how your installation behaves at the connection point, and a storage system behaves differently from a simple grid-tied one. If the paperwork describes a system without storage and the real installation has a battery, you have a mismatch that can surface at inspections, at the meter, or when the certificate is issued.

Your injection power stays limited to the approved value

The ATR (Aviz Tehnic de Racordare — Technical Connection Approval) issued by the operator sets out the technical solution and the approved power. A battery does not raise that ceiling: the power you may inject into the grid remains limited to the value approved through the ATR, and the inverter is configured to respect it. If you need a higher approved power, that is a separate request to the operator, independent of storage. Details about the approval itself: Technical Connection Approval (ATR).

The certificate of connection reflects the final configuration

At the end of the process, the operator issues the certificat de racordare (certificate of connection), which records the final, real configuration of your installation. This is precisely why the battery must be in the documentation from the start — or added to it properly later.

Adding a battery to an already-certified system

A very common 2026 scenario: you connected a simple grid-tied system a year or two ago, and now you want to add storage. It is possible, and retrofitting is increasingly popular, but it is not “plug in and forget”.

Changing the configuration of a certified prosumer installation means updating the documentation held by the operator, in line with the operator’s procedures: the new hybrid configuration and the storage equipment, with its certificates of conformity, are declared so that the operator’s records match reality. The exact steps depend on the procedures in force at the time, so treat blanket internet advice with caution and check before you buy equipment.

What you should not do is add the battery silently. The cost of updating the paperwork is small; the cost of an installation that no longer matches its certificate is an open-ended problem.

Three-phase, power and other practical details

Storage-ready hybrid inverters for larger homes are often three-phase. If your property currently has a single-phase supply and you are planning a larger solar-plus-storage system, evaluate early whether you need a three-phase connection (works from 2,900 lei) — it is far cheaper to solve this at the design stage than after the panels are on the roof.

Also worth knowing: storage systems appear in the Casa Verde programme run by the AFM, under the conditions of the guide in force. If you plan to apply, check the current guide before you lock in the system configuration.

Where we fit in — and where we do not

To be transparent about scope: SUN WATT does not sell or install panels or batteries. We are an ANRE-certified company (certificate no. 19761) and we handle the grid-connection side for prosumers in Bucharest, Ilfov and Giurgiu:

• the connection dossier and design — from 900 lei;
• assistance with obtaining the ATR — from 350 lei;
• the DIU (utilisation installation dossier) — from 1,200 lei;
• liaison with Retele Electrice Romania S.A., through to the bidirectional meter and the certificate of connection.

For the complete prosumer grid connection service, the cost is established through a personalised quote, because it depends on the system and the conditions at the location.

The bottom line

• A battery is not required to become a prosumer — it is an economic choice, not a legal one.
• With storage you inject less and self-consume more; the connection process itself stays the same.
• A hybrid system with a battery must be declared in the connection documentation, and the injection power stays at the value approved in the ATR.
• Adding a battery to a certified system means updating the documentation with the operator, in line with its procedures — never silently.

If you are planning a solar-plus-storage system, or you want to add a battery to an existing prosumer installation, talk to us before you commit to equipment. We will tell you exactly what the connection side requires — honestly, including when you do not need our help. Call 0733 097 440 or write to us via the contact page.