In short
Capacity is the amount of energy a battery can store, in kilowatt-hours (kWh). Power, in watts (W) or kilowatts (kW), tells you how fast it charges and delivers electricity.
How many kWh does a home battery have?
Home batteries come in different sizes: a small one stores 2 kWh, a typical one about 6 kWh and a large one about 20 kWh. Bigger is not automatically better. A home battery should cover your evening and night consumption, and you should not choose one that is too big. Also read what changes on 1 January 2027.
On a sunny summer day even a much larger battery is quickly full, and in winter panels produce too little to fill it. So do not size capacity on the surplus of the summer peak, but on your own consumption.
Calculating capacity in three steps
Step 1: find your daily consumption. Divide your annual consumption in kWh by 365. You find your consumption on your energy bill or smart meter, and with a P1 meter in the meter cupboard you can also measure how much you use in the evening and at night. Do you not know your consumption? A Dutch household uses on average 2,430 kWh of electricity a year, about 6.7 kWh a day. Your own consumption is always better than an average.
Step 2: take the share the battery should cover. A battery should be able to cover your evening and night consumption. We therefore calculate with 60 to 80 percent of your daily consumption: during the day you use part of your electricity straight from your panels, the rest falls in the evening and at night. At 10 kWh a day that means a battery of 6 to 8 kWh. Do you know exactly how much you use after sunset from a P1 meter? Then use that number.
Step 3: Check the result against your panels. Our second rule of thumb is 1 to 1.5 kWh of capacity per kWp of panels. This keeps the battery from being so big that your panels cannot fill it on an ordinary day, or so small that it is already full in the morning on a sunny day. Ten 400 Wp panels make 4 kWp, so 4 to 6 kWh. If the results differ a lot, start with the lower one and choose a model you can expand later.
| Step | Calculation | Result |
|---|---|---|
| Annual consumption | Example household without large consumers | 3,200 kWh |
| Daily consumption | 3,200 kWh ÷ 365 | about 8.8 kWh |
| 60 to 80 percent of daily consumption | 8.8 kWh × 0.6 to 0.8 | about 5.3 to 7.0 kWh |
| Check against panels | 10 panels × 400 Wp = 4 kWp, × 1 to 1.5 | 4 to 6 kWh |
Where do these rules of thumb come from?
Both rules are rules of thumb that we at Voltravo use to pick a first size. There is no official standard for them. They assume: (1) a household without large electricity consumers such as a heat pump or an electric car, (2) solar panels on a typical roof, (3) a battery that mainly shifts your own solar power to the evening. With a heat pump, an electric car or a dynamic contract, a different size may fit better. The battery match takes that into account. Rules 60-80% of daily consumption and 1-1.5 kWh per kWp: our own rules of thumb at Voltravo.
Nominal or usable: what do you actually get?
Look at which capacity a manufacturer quotes. Nominal is what fits in the cells, usable is what you actually get out. So look at the depth of discharge: at 90 percent depth of discharge you get about 4.61 kWh out of a 5.12 kWh battery. If a product page only lists the total capacity, count on less to be safe.
In the shop product data, usable capacity is given for two models: the Marstek Venus E 3.0 has 5.12 kWh and a depth of discharge of 90 percent (about 4.61 kWh usable), and the AEG Solarcube about 5.43 kWh usable out of 6.028 kWh. For the other models the shop only lists total capacity.
Capacity, power and expansion per model
Capacity tells you how much you store, power how fast the battery charges or delivers. Both are on the product page. The table compares the batteries in the shop.
Know how many kWh you need? Put it next to power, connection, phase and warranty in choosing a home battery.
| Model | Capacity | Usable | Charging and discharging | Expansion |
|---|---|---|---|---|
| Marstek Venus E 3.0 | 5.12 kWh | about 4.61 kWh (90% depth of discharge) | charging max. 2,500 W | max. 3 per phase (15.36 kWh); with SmartBox up to 9 across 3 phases |
| Hyxi Halo | 3.014 to 18.086 kWh | not stated | 1,500 VA, 3,000 VA with extra module | up to 6 modules (18.086 kWh) |
| TSUN PowerTrunk | 5.12 kWh | not stated | max. 2,500 W AC | max. 4 units on one phase (20.48 kWh) |
| AEG Solarcube | 6.028 kWh | about 5.43 kWh (90% depth of discharge) | max. 3,000 W | no expansion listed |
| Hoymiles HiBattery 1920 AC | 1.92 kWh | not stated | 1,000 VA nominal (800 VA to the grid) | no expansion listed |
Expand later or go bigger now?
Some of the batteries in the shop are modular: you start small and add modules later, as the table shows. That helps if you turn out to need more later. Check the maximum and the rules per phase beforehand, as in the table. The Hyxi Halo 3 kWh is an example of a small start with room to grow.
For a home where an installer arranges the whole setup there are also home batteries with installation, such as the KSTAR BluE-S from 5.12 to 20.48 kWh nominal according to the manufacturer. Not sure which model fits your home? The battery match asks a few questions about your home and your goals. More on what a battery does and does not do is in what is a home battery.
According to RVO, only batteries of 5 kWh or more count towards the energy label. Read more in home battery and energy label.
Sources
- Milieu Centraal: home battery: 2, 6 and 20 kWh, do not choose too big, P1 meter, 15 kWh output in June
- Milieu Centraal: solar power when net metering ends: example household with 3,200 kWh a year
- Milieu Centraal: average energy consumption in the Netherlands: average of 2,430 kWh of electricity a year (accessed on 2026-10-13)
