Do you already have solar panels and want to use more of their energy in the afternoon or evening? Adding a battery can also be considered after the initial installation. However, it is not enough to choose a capacity and connect another piece of equipment. First, the existing inverter, electrical installation and permitted operating mode for your system need to be checked.
The key question is specific: can you keep your existing equipment, or does the upgrade require changes? The guide below will help you prepare for a meaningful technical assessment before requesting a final quote.
Start with the details of your existing system
Do not rely only on the inverter brand or the total power of the panels. Gather the exact model number, installation date, available technical documents and the electrical diagram you received.
The Connection Agreement, details of your net-metering arrangement and access to the monitoring app are also useful. This allows the engineer to assess what has been installed and approved, rather than planning the upgrade based on assumptions.
Send clear photos of the equipment nameplates, if you can take them safely. Do not open covers or electrical panels to find more information. To learn about the inverter’s role, read our guide to inverters in solar systems.
The two main options for adding a battery
Keep the solar inverter and add a storage system
In an AC-coupled solution, the existing inverter continues to convert the panels’ direct current into alternating current. The battery connects through its own inverter on the installation’s AC side.
This may allow you to keep the existing inverter, but that does not mean every combination is suitable. The metering, controls and protection systems need to be designed as a whole. SMA describes this upgrade option using a battery inverter as one of the available technical choices.
Use a compatible hybrid inverter
In a DC-coupled configuration, the battery and solar panels work together through a suitable shared inverter. If your inverter already supports this function, adding an approved battery can be considered. Otherwise, the inverter may need to be replaced or a different architecture may be required.
If replacement is proposed, ask for compatibility with the existing panel strings and their electrical characteristics to be checked as well. Keeping the panels does not mean that any new inverter will be compatible with them.
Some product ranges allow storage functions to be activated through a software update. For example, Fronius describes UP.storage for the GEN24 series, noting that availability varies by country. Ask for confirmation for the specific model, installation country and total activation cost.
What actually proves compatibility?
The descriptions “hybrid” or “battery-ready” are no substitute for technical documentation. Before ordering, ask for the following to be specified:
- The exact inverter and battery combination supported by the manufacturer.
- The required number of battery units and the permitted operating limits.
- The required software versions and any additional communications equipment.
- The available functions and limitations with this configuration.
In the Fronius compatibility tables, for example, support is listed by model and configuration. A general product catalogue or a verbal assurance that “all batteries work together” is not enough.
Check what surplus energy you have during the day
Your annual electricity bill is useful, but it does not show when you generate energy and when you need it. To assess storage, look for production, consumption and grid exchange data throughout the day and across different seasons.
Suppose two homes have the same solar capacity. Several appliances run at midday in the first, while consumption in the second is concentrated after sunset. This does not automatically mean they need the same battery. This is a hypothetical example that shows why sizing needs to be based on your actual usage profile.
Ask separately for the usable storage energy in kWh and the charging and discharging power in kW. The first describes the amount of energy that can be used, while the second limits the rate at which it can be transferred. Factor in losses and any reserve you want to maintain.
Do not overlook the meter and inspection of the installation
Battery management needs to know the energy flow at the appropriate point. An app that only shows panel production is not always sufficient. The installer must confirm whether compatible metering equipment is already in place or whether new equipment is required.
The HEDNO describes the role of the energy direction sensor and the control system. In your Your installation also requires checking the electrical panel, protective devices, power supply and available space, in line with the specific equipment.
Clarify the process before committing
The technical feasibility of adding a battery does not, by itself, confirm that the change can be activated under any configuration. Ask the responsible engineer to check the applicable process with HEDNO, the required documentation and the terms of your existing contracts.
In particular, clarify who will handle the application, whether metering will be affected and which functions will be permitted. Do not assume that charging from the grid or feeding stored energy into the grid will be allowed just because the app shows an option for it.
If you also want the system to operate during a power outage, ask for a separate description of its backup capability. A battery for increasing self-consumption does not automatically guarantee backup power; see our guide to backup power.
Request a quote for a complete upgrade
Compare proposals that specify what will be retained, what will be replaced and which tasks are included. In addition to the battery, look for costs for an inverter where required, metering, protective devices, wiring, software, technical procedures and commissioning.
Also ask what data you will be able to view after handover and who will support the complete system. If you need help evaluating the proposals, use our guide to comparing quotes.
At Solar Home, we design solar PV systems with storage to meet your property’s needs. Contact us with details of your existing installation so we can assess which upgrade solution may be right for your situation.
