Group purchase home battery: what does it leave out?

A group-purchase battery leaves out whatever is not in the standard package. That is usually back-up in a power cut, three-phase power for a large home, control beyond self-consumption and a design based on your own data. For an average house that is fine. For a large, all-electric home that must keep running, a home battery designed by a specialist does what a package cannot.

A folder or an e-mail from your province arrives: a group purchase for solar panels and home batteries. It looks simple and safe. You register, and a proposal follows. One buyer shared his offer on a Belgian forum and asked what others thought. Another posted his group-purchase quote on a building forum: a single-phase inverter of 3 kW with 5.12 kWh. The first reply was blunt: "you can only draw 3 kW from your battery".

That is the real question for a large home. A standard package is designed for a standard house. Your house has a heat pump, an induction hob, a car charger and maybe a home office. When the street goes dark, a standard hybrid battery often goes dark with it. Adding back-up or a second and third phase later usually means a new inverter and new wiring.

In Kortenberg the home runs on three-phase batteries with full back-up in off-grid mode, with 9 kVA and 30.8 kWh. That is not a package; it is a design for one house.

How does a group purchase for home batteries work?

You register for free, the organiser picks the supplier, and you decide after a site visit. Provinces and other organisers bundle demand, so the chosen supplier can offer one package at one price to many homes.

The province of East Flanders has run a campaign for solar panels and home batteries four times a year since 2023. Its public pages explain the steps above. The supplier is "the winning supplier": the organiser chooses it, not you. One East Flemish municipality adds that the group purchase counts on at most 10 kWp of solar panels, about 40 panels.

What does a group purchase do well?

It gives you a fair reference for a standard battery, with little effort and no obligation. For many homes that is exactly what they need.

• A benchmark: forum readers advise using the group-purchase offer as a yardstick next to local quotes.
• A vetted supplier: the organiser selects the supplier and checks the campaign.
• Energy management included: the East Flemish battery campaign describes an energy management system (EMS) that uses your own solar power smartly.
• Simple steps: one proposal, one site visit, one installer.

Do you want a battery that stores daytime solar power for the evening? And is a power cut a nuisance rather than a problem? Then a group purchase can be a sensible choice. The question is what happens when your house is not standard.

What does a group-purchase home battery leave out?

Mostly what a large home needs most: back-up, three-phase power, deeper control and a design on measured data. Not every campaign is the same, so treat the table as a checklist for any offer.

The public pages of the East Flemish battery campaign describe the EMS and the hybrid inverter. We found no mention of back-up or phases there (checked in September 2026). That does not mean it is impossible; it means you have to ask.

Does a group-purchase battery keep your house running in a power cut?

Only if the offer says so in writing. A home battery keeps your house running only when it has a back-up output and your circuits are connected to it. A grid-tied system switches off when the grid fails, as the rules require.

Many owners discover this during their first power cut. The sun shines, the battery is full, and the house is still dark. The inverter follows the grid rules and stops. For an average house that is a nuisance. For a home with a heat pump, a well pump or a home office, it is the moment the battery should have earned its place.

Back-up comes in levels: an emergency socket, a few essential circuits, or the whole house. Our guide to a home battery with backup power explains the three levels and how fast each one switches over. With our systems the inverter takes over within 20 milliseconds, fast enough for computers to keep running.

Is a standard package powerful enough for a large, all-electric home?

Storage is only half of it; power decides what can run at the same time. A battery of 10 kWh behind a 3 kW inverter still delivers only 3 kW.

The forum buyer with the 3 kW inverter planned to cook, run the dishwasher and use the evening lights from the battery. The replies pointed out that cooking together with other appliances exceeds 3 kW. In a large home with a heat pump and induction, the gap is bigger still. And on a three-phase connection, a single-phase battery only covers one phase.

Whether you need a three-phase battery, and how much power each phase gets, is a question of its own. Read our guide on a three-phase home battery for full back-up. In Wetteren the whole house runs through the battery on three phases, with 9 kVA and 15.4 kWh.

What should the battery control beyond self-consumption?

In a large home the battery is part of the energy system, not a box on the wall. It should work with the solar panels, the grid, the peaks and, where needed, a generator.

• Peaks: in Flanders, the battery helps on the capacity tariff when it supplies the heavy loads, not only when it stores solar power.
• Monitoring: you see what you produce, use and store, locally and remotely, in the free VRM app and portal.
• A generator: with a GX controller the system can start a back-up generator automatically during a long outage.
• Your existing inverter: we can connect almost any type of solar inverter to the home battery.

Already have an SMA or SolarEdge installation? Read how to add a battery and back-up to an existing installation without replacing everything.

Group purchase or specialist: which one fits your house?

Choose by what your house must do, not by the label on the offer. Both routes have a place.

Which questions should any home battery offer answer?

Put the same five questions to every offer, group purchase or not. The answers show what you really buy.

How do we design a premium home battery?

We measure first, decide with you what must keep running, and design for your house. Our team has three certified battery specialists.

1. Step 1: We take the necessary measurements before we design anything.
2. Step 2: Together we decide which systems and appliances stay on in a power cut; we can connect them separately to the battery.
3. Step 3: We size the power and the storage, and choose from a wide range of batteries with a modular, expandable design.
4. Step 4: We install and commission the system, and you follow it in the free VRM app and portal.

Our home batteries come with a 10-year warranty on retained power, and we also maintain and repair existing battery systems. Want to see what our home batteries with back-up can do for a large home? Or check first which home battery really works off-grid?