Home battery: good idea?
There is more and more interest in the home battery. For many people, off-grid is an attractive idea. Or a nice extension after buying solar panels and an electric car. The supply of home batteries is growing. What can you do with a home battery? And is it a good investment?
Which home battery do we mean?
There are batteries for storing heat and electricity. We restrict ourselves here to electricity storage. Storing electricity can be done in several ways. This article is about batteries based on a chemical reaction, as in a lithium-ion, lithium iron phosphate and nickel-metal hybrid battery.
Wat is de techniek van de thuisbatterij?
The supply of home batteries is diverse. For instance, batteries differ in useful storage capacity, peak power and energy loss (‘round trip efficiency’). There are also differences in weight, noise, fire safety, environmental aspects and expected lifetime. There are also differences in battery connection. Connected directly to solar panels, they work on direct current, which has the advantage of losing less power compared to batteries that work on alternating current. Interested parties are referred to two articles, see section Articles hereafter.
Off-grid?
Solar panels mainly produce power in the months of April to September. To cover your needs in the winter months with your own power, you would have to have a huge number of solar panels. Or a huge storage capacity. Both solutions are not feasible in practice. The idea of being completely self-sufficient and living off-grid is not realistic.
What can you do with a home battery?
There are four uses for the home battery that are indeed realistic. First, you can increase your self-consumption. Self-consumption is the part of the electricity output that you do not supply to the public grid, but consume directly at home. For example, by storing power for use at night.
By extension, the home battery is also a way to avoid peak load on the electricity grid. At peak loads, solar panels are switched off. If enough households have a battery, there is less chance of peak load. Incidentally, you can ask your grid operator how often solar panels are switched off in your neighbourhood. In many districts, this is not too bad.
The third use is the battery as a trading platform: you charge the battery with cheap power and discharge the battery when the price is high.
Finally, the fourth use case is the home battery as a noodstroomvoorziening. This is only a limited benefit. In the Netherlands, the power supply is only interrupted for 52 minutes a year. It is nice if you can still run your fridge at those times, but we don't think many people buy a battery for this purpose.
You can make money with two of the mentioned uses: increasing the share of self-consumption and the trading platform. We will elaborate on these earning models in concrete terms below.
What does a home battery cost?
Voordat we kijken naar de mogelijke winst eerst even de aanschafprijs. Reken op een prijs van 5.000 euro voor een thuisbatterij met 5 kWh opslagcapaciteit, 7.500 euro voor 10 kWh en 12.500 euro voor 20 kWh. Deze prijsindicatie is inclusief de kosten van installatie, maar exclusief BTW. De BTW kunt u namelijk, onder voorwaarden, terugvragen van de belastingdienst.
How much does higher self-consumption yield?
Many energy suppliers charge a feed-in fee when you feed electricity back to them. Some apply a fixed tariff, independent of the amount of electricity delivered back. Others apply a variable rate per kWh. Here, we assume a variable feed-in tariff of 9 euro cents per kWh.
Without a home battery, your self-consumption is about 33 per cent of generation. You supply the rest, 67 per cent, to the public grid. On average, the feed-in cost is then 6 euro cents per kWh of self-generated electricity (67% x 0.09).
With a home battery, you can increase the proportion of self-consumption to 50 per cent, we estimate. The average feed-in cost then becomes 4.5 euro cents per kWh of electricity produced by the solar panels. So you save 1.5 euro cents per kWh of electricity produced at home. See the breakdown in the table below.
If your solar panels produce, say, 3,000 kWh per year, the home battery will save you 45 euros per year. You will therefore not recoup the purchase price of the home battery.
How much do you earn from trading?
By buying at a low price and selling at a higher price at another time, you are trading electricity. This is possible if you have a fixed or variable energy contract due to the difference between the high peak and low off-peak tariff. However, this price difference is so small that you cannot recoup the home battery within its lifetime.
There is a bigger price difference with hourly rates. Hourly rates you have if you have a dynamic energy contract.
The biggest price difference can be realised on the imbalance market. On that, prices fluctuate quarterly. This market is only accessible to energy suppliers, not to individuals. To trade on the imbalance market, the energy supplier needs to be able to control your home battery. They charge the battery when the price on the imbalance market is low and discharge it when the price is high.
Zonneplan, a company that offers home batteries, estimates that with the tariffs of a dynamic energy contract, you pay back the home battery in 10 years, and in the imbalance market in 5 years.
But an electric car is also a home battery, right?
Indeed, an electric car can also serve as a home battery. With bi-directional technology, you can feed power from the car back to a single device (‘vehicle-to-load’), to your household (‘vehicle-to-home’), or even to the public grid (‘vehicle-to-grid’). Before this becomes commonplace, there are still some challenges in terms of taxes, supply and technology. In addition, you need to ask yourself how often the car is at home during the day. If you use the car for work, it cannot be used as a battery at home during the day.
Where do I buy a home battery?
Providers of home batteries are installers and power companies. As the battery is part of your electrical installation, we recommend having it installed by a professional.
Is my house suitable?
For a home battery, you need 1 square metre of floor space in an insulated, dust-free room. Also take into account the battery's weight and noise. Depending on the type of battery, a 3-phase connection is required.
Home battery: Yes or No?
A home battery was already a good idea for the common good: using more of your own power at home and helping to avoid peak loads. Now, with the offer of home batteries that act on imbalance, you can also count on a short payback period. So we think buying a home battery is a good idea! Provided you have the space to do so, of course.
Articles
For more information on the topic of home batteries, please refer to:
