How many kWh of home battery do you need? How to calculate the right capacity
Last updated: 26 September 2026 · By Team Multi-Solar, home batteries since 2022, Rotterdam
For most households with solar panels, the right capacity is between 5 and 10 kWh. The exact figure follows from three things: how much electricity you use in the evening and at night, how much your panels generate during the day, and whether you have a dynamic energy contract. Below are three calculation methods you can use to work this out yourself, plus one check that almost nobody does: how much you can actually use via a wall socket.
Which capacity suits which household?
A first direction, before you start calculating. The ranges are indications based on consumption and generation, not a guarantee: two families with the same annual consumption can have a very different evening pattern.
| Household | Annual consumption (indication) | Solar panels | Capacity | Where to find it |
|---|---|---|---|---|
| One person or apartment | up to about 2,000 kWh | none or a small number | 2 to 3 kWh | plug & play home batteries |
| Average household | around 2,500 kWh (Milieu Centraal: 2,430 kWh) | 8 to 12 panels | 4 to 6 kWh | plug & play home batteries |
| Large family or heat pump | 4,000 to 6,000 kWh | 12 to 20 panels | 8 to 12 kWh | plug & play expanded or fixed home batteries |
| Heat pump, EV charger and dynamic contract | more than 6,000 kWh | 16 or more panels | 10 to 15 kWh or more | fixed home batteries |
The full range, sorted by capacity, can be found in the overview of home batteries.
First this: kWh is capacity, kW is speed
Two figures you see on every product page and that are often confused.
kWh (kilowatt-hour) is the capacity of the battery: how much electricity it can store. A 5 kWh battery can supply 1,000 W for five hours, or 500 W for ten hours.
kW (kilowatt) is the speed: how fast the battery charges and how fast it supplies electricity to your home. A plug-in home battery supplies a maximum of 0.8 kW (800 W) via the wall socket. On a dedicated circuit in the meter cupboard, a Marstek Venus E 3.0, for example, supplies 2.5 kW and a fixed battery such as the Venus X 6 kW.
When choosing the capacity, you calculate in kWh. But the power in kW determines whether you can actually use those kWh at the moment you need them. More on that below in the 800 W check.
Method 1: how do you calculate the capacity based on your evening and night-time consumption?
This is the method that comes closest to reality for most households, because a battery mainly covers consumption during the hours when your panels are not producing anything.
- Take your annual consumption from your annual energy statement and divide it by 365. At 3,000 kWh per year, that is about 8.2 kWh per day.
- Estimate which share you use in the evening and at night. Without a heat pump, this is often well over half: cooking, TV, lighting, dishwasher, washing machine after work. Use 55 percent if you do not know: 8.2 × 0.55 = 4.5 kWh.
- Add a 20 percent margin for losses during charging and discharging and for days that are a little heavier: 4.5 × 1.2 = 5.4 kWh.
In this fictitious example, you end up in the 5 kWh class. If you have a smart meter with an app or an energy monitor, look at your actual consumption between six in the evening and seven in the morning; that is more accurate than a percentage.
Method 2: how do you calculate the capacity based on your solar panels?
A battery can never store more than your panels have left over. That is why your panel output is the second limit.
Milieu Centraal calculates with a set of eight 435 Wp panels (3.48 kWp in total) that supplies about 3,000 kWh per year; that comes to roughly 860 kWh per kWp per year. The common rule of thumb for storage is 1 to 1.5 kWh of battery capacity per kWp of panels.
| Panel output | Number of panels (435 Wp) | Capacity (1 to 1.5 kWh per kWp) |
|---|---|---|
| 2.6 kWp | 6 | 2.6 to 3.9 kWh |
| 3.5 kWp | 8 | 3.5 to 5.2 kWh |
| 4.4 kWp | 10 | 4.4 to 6.5 kWh |
| 5.2 kWp | 12 | 5.2 to 7.8 kWh |
| 7.0 kWp | 16 | 7.0 to 10.4 kWh |
Why not bigger? In June and July, on a good day your panels generate several times your evening consumption. A battery that stores all of that surplus is largely empty for the rest of the year. So choose the capacity based on an average spring or late-summer day, not on the summer peak. Whatever still goes to the grid in summer is not lost electricity, even after the end of the Dutch net-metering scheme (salderingsregeling) in 2027: you receive a payment for it.
Method 3: how do you choose the capacity with a dynamic energy contract?
A battery can also make sense without solar panels. With a dynamic contract, the electricity price varies by the hour; the battery charges during cheap hours (often in the middle of the day and at night) and supplies power during expensive hours (usually between five and nine in the evening).
The capacity you need is then your consumption during those expensive hours, with a 20 percent margin:
- Consumption between 17:00 and 21:00: for example 3 kWh (cooking, TV, lighting, dishwasher).
- With margin: 3 × 1.2 = 3.6 kWh.
- If you also want to cover the morning peak, add that on top.
With this method, power (kW) counts for more than with the other two: the battery must be able to fill up in a few cheap hours and supply power fast enough during the expensive hours. A battery that charges at 2,400 W, such as the Zendure SolarFlow 2400 AC+, is filled with 2.4 kWh in about an hour.
The 800 W check: how many kWh can you really use via the wall socket?
This is the check that most calculators skip. A plug-in home battery that supplies power via the wall socket may give your home a maximum of 800 W. That means:
800 W × 10 hours of evening and night = a maximum of 8 kWh that you can draw from the battery in one night, and only if your home demands 800 W or more throughout that night. In practice, a home often demands 200 to 400 W at night, so you use 2 to 4 kWh.
A plug-in home battery of 10 kWh or more that only supplies power via the wall socket is therefore rarely the best first step. Buying bigger does make sense if:
- you have an installer put the battery on a dedicated circuit (installation via a quote); then, for example, the Venus E supplies 2,500 W and the HYXi HALO 1,500 W (premium setting, by a qualified installer);
- you place a second battery on another phase, so that each phase gets 800 W;
- you have a dynamic contract and the battery charges and discharges more than once a day.
Why that 800 W limit applies and exactly what is permitted is explained in our article on the plug-in home battery and the 800 W rule.
Heat pump, induction or EV charger? Calculate bigger and look at power
With a heat pump, your consumption shifts to winter and to the night, exactly when your panels produce little. In that case, calculate with your winter consumption rather than the annual average. Even more important: a heat pump or induction hob demands several kW at peak moments, and a plug-in home battery cannot supply that via the wall socket.
- Heat pump or induction: the power in kW matters more than the capacity. A fixed battery in the meter cupboard, or a plug-in home battery on a dedicated circuit, is a better fit here. Installation goes through a quote.
- EV charger: a car charges at 7 to 11 kW and drains a 10 kWh battery in an hour. Charge the car during the day on solar power, and use the battery for the house.
- Three-phase connection: many fixed systems balance per phase. What your connection is and why it matters is explained in single-phase or three-phase.
Usable capacity, expanding and starting small
A product page shows the nominal capacity. How much of it you can actually use depends on the depth of discharge permitted by the manufacturer. With modern LiFePO4 batteries, this is high: the Marstek Venus X allows 90 percent, the Anker SOLIX Solarbank Max AC 100 percent. Look in the datasheet on the product page for “DoD” or “usable capacity”.
The good news: you do not have to guess right in one go. Almost all plug-in home batteries are modular.
- The Marstek Venus A starts at 2.12 kWh and grows with modules up to 12.72 kWh.
- The Zendure SolarFlow 2400 AC+ starts at 2.4 kWh and grows with 2.88 kWh modules up to 16.8 kWh.
- The HYXi HALO starts at 3 kWh and grows with 3 kWh expansion modules up to 18 kWh.
Our advice: start at the lower end of your range. The included P1 smart meter dongle (P1-meter) and the app show you exactly, after a few months, how often the battery is full and how much you still feed back to the grid. Based on that measurement data, you choose an expansion module, or not. How that measurement works is explained in our article on the P1 meter.
Frequently asked questions
Is 5 kWh enough for a home battery?
For an average household with 8 to 12 panels and an evening consumption of 3 to 5 kWh, usually yes. Via the wall socket, a plug-in home battery supplies a maximum of 800 W; in a 10-hour night, that is at most 8 kWh, in practice often 2 to 4 kWh because a home demands 200-400 W at night. If your consumption grows, you expand with a module.
How many kWh of home battery do I need with a heat pump?
Calculate with your winter consumption and look mainly at the power. A heat pump draws several kWh at night and peaks at several kW; that calls for more like 8 to 12 kWh and a fixed battery or a dedicated circuit. Request a quote for this.
How big should a home battery be with a dynamic energy contract?
As big as your consumption during the expensive hours, usually between five and nine in the evening, plus a 20 percent margin. For many households, that is 3 to 6 kWh. Charging power is more important here than with solar panels: the battery must be able to fill up in a few cheap hours.
Can I expand later if I start too small?
Yes, with virtually all the plug-in home batteries we sell. You buy an expansion module of the same brand and add it alongside or underneath. Note the maximum capacity per brand, which is listed on every product page.
How many kWh do my solar panels generate per day?
Averaged over the year, about 2.3 kWh per kWp per day (from 860 kWh per kWp per year), but in June it can be double that and in December a fifth. Your inverter app or energy monitor shows the actual daily yield; use that for your calculation.
Torn between two sizes? Request a no-obligation quote and send us your annual energy statement, and we will work it out with you.
Sources
- Milieu Centraal, “Gemiddeld energieverbruik” (average energy consumption) (page of 4 September 2026): 2,430 kWh of electricity per household per year
- Milieu Centraal, “Kosten en opbrengst zonnepanelen” (costs and yield of solar panels) (page of 29 June 2026): eight 435 Wp panels supply about 3,000 kWh per year
- Product data Marstek Venus A, Venus E 3.0 and Venus X, Zendure SolarFlow 2400 AC+, HYXi HALO and Anker SOLIX Solarbank Max AC: manufacturer documentation and product pages on multi-solar.nl (26 September 2026)