Whether a home battery is profitable varies per home. Two homes with the same number of solar panels can have a completely different result. If you use a lot of electricity during the day, there will be less left to store. If you use mainly in the evening, you can use stored solar power more often. The capacity, power, your energy rate and the settings also play a role.
A good assessment therefore starts with the data from your digital meter, not with the largest battery pack. 15-minute readings show when you put power on the grid, when you draw power again later and which peaks return. This way we see how much energy a battery can shift on normal days and what part of its capacity would remain unused.
The examples with monthly peaks and the Flemish capacity tariff in this guide apply to Flanders. In Brussels we calculate with the applicable Sibelga grid rates and look at the existing solar panels and any green energy certificates separately. A lower quarter-hour peak does not automatically mean the same savings.
15-minute readings tell more than your annual statement.
The amount of electricity you export in a year does not show when that electricity is available or how much you will need later the same day. A battery is mainly suitable for storing energy over a short period. It can shift solar electricity from afternoon to evening, but cannot keep a large summer surplus until winter. We therefore compare generation and consumption in 15-minute intervals and across the seasons.
We look for patterns that regularly recur: how much surplus remains after direct home consumption, how much power do you use again later and how often can the battery usefully charge and discharge? One exceptionally sunny day or one expensive winter week may not cover the entire investment.
- The electricity you put on the grid shows how much production you do not use immediately.
- Your subsequent grid consumption shows how much stored energy you can use yourself.
- Data from different seasons prevents a calculation based on only ideal summer days.
- 15-minute peaks help assess the required output power.
Capacity and power are two different choices.
Capacity, expressed in kWh, determines how much energy the battery can store. Power, expressed in kW, determines how quickly it can charge or discharge. A system can therefore contain a lot of energy but deliver too little power to absorb a short high peak. Conversely, a powerful but small battery can run out quickly.
You can expand the 2400 AC+ with separate battery modules. Expansion batteries are currently not available for the 4000 Mix; more storage requires additional complete devices. We prefer to choose a capacity that you use often than an oversized package that remains half empty for long periods. A heat pump, induction hob, boiler and charging station help determine how much power you need.
More than just saved energy determines the result.
A stored kWh has value when you later buy less electricity from the grid, take advantage of a favorable price difference or limit a consumption peak. On the other hand, there are the purchase and installation, conversion losses, self-consumption and wear and tear of the system. Energy management can also entail costs. The difference between your purchase price and injection fee is therefore important, but not the only figure.
Calculations that assume a complete ideal cycle every day are usually too optimistic. In winter there is less solar surplus; on some summer days you cannot completely empty the battery for the next production. A realistic calculation calculates multiple scenarios and shows which assumptions most influence the result.
Is it interesting to charge your home battery via the grid in winter?
In winter there is often too little solar surplus to fill the home battery. With a dynamic contract, an existing battery can store power from the grid during cheap hours and avoid more expensive purchases later. This is not automatically interesting as soon as the wholesale electricity price is a little lower. The supplier formula, grid costs, conversion loss, battery wear and any higher monthly peak together determine the result.
We tailor the control to the charging station, heat pump and other heavy appliances, so that simultaneous grid charging does not unnecessarily increase your monthly peak. Charging an electric car directly during a cheap time slot is more efficient than first sending the same electricity via the home battery. A good arrangement only charges the home battery when the expected price difference is large enough, there is actual consumption later and the charging power remains below the desired home peak.
Technical calculation for dynamic rates.
Compare the costs that actually change when you purchase one extra kWh from the grid. Use the energy price according to your supplier formula, supplemented with grid costs and levies charged per kWh consumed. Count on the same VAT basis everywhere. Fixed subscription costs and the existing capacity tariff are not included in the price per additional kWh.
A simplified formula per kWh delivered later is: margin before additional capacity costs = high variable purchase price − low variable purchase price ÷ return − wear and tear. The high price is what you would pay at a later time of consumption; the low price is what you pay during grid charging. Both prices already include applicable variable costs.
Dividing an average annual grid rate by the annual consumption does not provide a suitable cost price for this calculation. That annual total also includes fixed and power-related amounts that do not change with each additional kWh. Check the individual rates on your contract and rate card. A negative wholesale electricity price also does not automatically mean that your final variable purchase price is negative.
The table uses fictitious variable purchase prices, not current market rates or promised savings. We calculate 90% overall efficiency between consumption from the grid and later delivery to the home. For 5 kWh of usable energy, 5 ÷ 0,90 = approximately 5,56 kWh is purchased. The actual efficiency and self-consumption differ per system and use.
In addition, we assume € 0,08 wear and tear per delivered kWh, or € 0,40 for 5 kWh. This is also a calculation assumption only. For your own calculation, use the part of the investment that you attribute to extra battery use. Also consider how much usable power the battery is expected to deliver over its entire lifespan. A product warranty in itself does not determine a fixed wear cost per cycle.
Add up the margins over your actual charging moments and deduct any additional capacity costs for the same period once. This way, a higher monthly peak is not charged again for each individual cycle.
In 2026, 1 kW billing peak costs an average of € 53,39 per year excluding VAT and applies at least 2,5 kW. Grid charging that does not increase the charged monthly peak does not cause any additional capacity costs. If the battery increases the peak from 2,5 to 2,9 kW each time for four winter months, then the indicative additional influence is approximately € 7,55 including 6% VAT. If she adds 2,4 kW to the peak each time during those four months, that is approximately € 45,27. The actual amount depends on your network area and billing period.
- Price basis: fictitious total variable purchase prices per kWh, including applicable VAT; fixed costs are excluded.
- Overall efficiency: 90% as calculation assumption.
- Wear and tear: € 0,08 per kWh supplied as calculation assumption.
- You assess any additional capacity costs separately over the same period.
| Fictitious variable purchase price | 5,56 purchase kWh | 5 avoid kWh decrease | Wear and tear | Margin before additional capacity costs |
|---|---|---|---|---|
| 10 ct cheap → 18 ct expensive | € 0,56 | € 0,90 | − € 0,40 | − € 0,06 |
| 10 ct cheap → 30 ct expensive | € 0,56 | € 1,50 | − € 0,40 | + € 0,54 |
| 2 ct cheap → 25 ct expensive | € 0,11 | € 1,25 | − € 0,40 | + € 0,74 |
Sometimes another measure yields more first.
Anyone who generates a lot of solar energy can first shift the use of large consumers to sunny hours. Smartly controlling hot water, washing machine, dishwasher, heat pump or car reduces the power you put on the grid, without additional conversion via a battery. An unnecessarily high consumption peak or poorly coordinated charging control also deserves attention first.
A battery becomes interesting for storing solar power when there is regular power left over that you can use later.
Charging at dynamic rates can also be a reason to consider storage; we assess the expected price benefit and the additional costs separately. A battery can also have value for comfort, energy management or emergency power, but these are separate purposes. For emergency power you need suitable hardware, safe switching and clear boundaries; Not every standard installation automatically powers your entire home in the event of a power failure.
This is how we assess whether a home battery suits your consumption.
You share your annual consumption and preferably 15-minute readings from Mijn Fluvius. We discuss solar panels, energy contract, heavy appliances, charging station and what you want to achieve with storage. We then compare usable capacity and power with the energy actually available on typical days.
We do not promise that every system will pay for itself within the same number of years. We show which assumptions most influence the result and choose a structure that you can actually use. If the data does not yet convincingly show that you will use the battery sufficiently, we will say so. A smaller or postponed installation is better than capacity that mainly remains unused.
Short answer
Frequently asked questions
What is the average payback period for a home battery?
There is no reliable average payback period that applies to every Flemish family. The result depends on the purchase price, the electricity you put on the grid and later purchase, your energy contract, grid rates, losses, wear and tear and control. Without your measurement data, a calculation remains an estimate, not personal advice.
See which revenues and costs countHow big should my home battery be?
The right size depends on how much electricity you can store on a regular day and use later. If the battery is too large, part of the storage often remains unused. You then pay for capacity that you rarely use. We look at your consumption per 15 minutes, the differences between the seasons and how much power the battery must be able to supply at the same time.
Read the difference between capacity and powerIs it interesting to charge my home battery via the grid in winter?
Sometimes. The electricity must be sufficiently cheaper when charging than when you use it. Compare all costs per additional kWh and also include energy loss and battery wear. Fixed subscription costs are not included in the cost of an extra kWh. We will assess any higher monthly peak separately. The sample prices in the guide are fictitious; your own contract and 15-minute readings determine the result.
Read how dynamic prices are settledSources