Energy storage at home - solar power

Storing solar energy at home instead of feeding it back to the electricity grid. It is possible with a home battery: a large battery in which you can store electricity. Some people are already trying them out in their homes. It is not yet financially attractive at the moment. But in the future, home batteries for solar panels may play a role in the energy supply. How does it work and what does it cost?

This is how home storage works

The power generated by your solar panels goes to the appliances in the house or to the electricity grid. But you can also connect a battery (a large battery) to the system in which you store power. You can then use that power later. How does that work?

1. The solar panels generate electricity.
2. The controller sends the generated power to the devices that need power at that time.
3. Are you generating more power than your devices are currently using? Then the 'surplus' of generated power goes to the home battery, so that you can use it later.
4. Only when the battery is full, the power is returned to the electricity grid.
5. If the solar panels do not generate power, but you do need power at home, the power is drawn from the battery.
6. As soon as the home battery is empty, the electricity is taken from the grid at a purchase rate.

If the sun does not shine, an empty battery can be charged with cheap off-peak power. You can then use that electricity later - at higher rates. This difference in rate is now very small (less than half a cent per kWh, price level January 2021). But in the future, the difference may become greater if more wind and solar are supplied to the electricity network. A battery system can respond to variations in supply and makes the network smarter ('smart grid').

A home battery is also called a home battery.

Storing solar energy: when is it beneficial?

The solar power that you do not use yourself goes through the meter box to the central electricity grid so that others can use it. The energy supplier checks the electricity you supply against the electricity you use. That's called netting. As a result, you get just as much for the solar power you supply as you pay for the power you purchase from the grid: about 22 cents per kWh (price level January 2021). If you supply more power to the grid than you withdraw from it, you will receive a feed-in fee. It is between 3 and 12 cents. Milieu Centraal charges 6 cents per kWh. You will find an example at Price and yield of solar panels  Click here to get more about energy storage systems.

The government wants to gradually phase out the netting scheme from 2023 . From 2031 you will only receive the lower feed-in fee for the electricity you supply to your energy company. That makes a home battery more attractive. This is especially true if the batteries are also cheaper.

Too much in summer, too little in winter

Even with a home battery, the connection to the electricity grid remains necessary. With a battery you can store electricity for several days; saving your bountiful summer flow for the dark winter is not possible.

With 9 solar panels, you annually generate about as much power as an average Dutch household consumes: 2700 kWh. That is an average of almost 7.5 kWh per day: as much as you can store with a large home battery. But there are big differences between summer and winter in the production of solar power.

On an average summer day in June, 9 panels can generate 13 kWh. The home battery can store 7.5 kWh and is therefore too small to collect all the solar power. And on an average December day, you generate far too little power with 2.5 kWh to cover your own consumption, so you hardly use the battery on such a day. The differences are even greater if you compare an extremely sunny summer day with a very gloomy winter day.

Grid connection remains necessary

For example, connection to the electricity grid remains necessary to absorb the overproduction in the summer and to compensate for the lack of production in the winter. In other words: it would be a shame not to make a grid connection, because then you throw away a lot of electricity in the summer when your battery is full. And it would also be unwise because then you won't have enough power in the winter, because your battery never gets full.

Solar energy storage costs

Home batteries come in different shapes and sizes. A small battery or battery can store 1 to a few kilowatt hours of electrical energy. But there are also large batteries of more than 10 kWh. Batteries or batteries can often be linked together, creating more capacity (we call this a modular system). Li-ion home batteries (Lithium batteries) cost €650 to €1300 per kWh of storage capacity. For a system of 10 kWh you pay approximately € 9,000. The prices of Li-ion batteries are likely to fall in the coming years. Lead-acid batteries are cheaper, but only deep cycle lead-acid batteries are suitable for storing solar power. The battery in electric cars can also be used as storage for solar energy. The current range of home batteries on the consumer market is small.