2024-07-04 20:00:56
GermanyIn recent weeks I have been asked several times whether small household batteries, such as those from HomeWizard in the Netherlands, are smart and/or useful. They certainly cost less than 1400 euros and are very simple to install. Plug it into a socket and establish a WiFi connection using the “dongle” and you are ready to go. It doesn’t get much simpler than that.
Only in the evening and at night
As I’ve often written, I’ve been waiting for years for batteries that can store a large portion of solar energy. Well, that’s really not what these little guys are for. With 2.7 kWh of capacity, the battery in my house is fully charged in fifteen minutes. Now I have a lot of solar panels, 34 of them, but if you have a standard set of solar panels, say 8 panels, in principle it would take less than an hour on a good day. The battery certainly won’t prevent you from returning on a sunny day and dealing with the return costs.
This little home battery “uses its own solar energy to help you get through the night”. That, in a nutshell, is what they’re for. If you don’t have a heat pump, this is probably true. A few hours of TV in the evening, with some lights on and maybe a cup of tea should be fine. That way you’ll still have some charge left for the next morning.
Return fees still exist
You can still use your own solar power in the dark which is a great idea. If you charge your batteries around midday it will also help relieve the strain on the grid. Great job both times.
But how much is a little? As mentioned before, the battery can store 2.7 kWh of power, with a maximum capacity of 0.8 kW. So three hours is regarding enough to fill it up. On a sunny summer day, your panels can easily provide 3 kW of power between 11 a.m. and 2 p.m. Of that, 0.8 kW is used to charge the battery. That leaves 2.2 kW to feed into the grid. But hey, every little bit helps.
Moderate “profit”
Assuming you can store 2.7 kWh of solar energy every day for a year (which is certainly impossible in winter), you can use 985 kWh of solar energy per year at night, rounded to 1000 kWh. If a kWh costs 25 cents, it is worth 250 €. This looks like a good profit. But: without the battery, you would provide 1000 kWh of electricity and can offset it later (at night and in winter). Then you might incur return costs of 5 to 10 cents, or 50 to 100 €. Your “profit” is actually just the saved return costs.
If netting disappears in 2027, the grid costs will also disappear and you will get “reasonable compensation” for each kWh supplied. If it is 10 cents I don’t mind. If you don’t give back 1000 kWh, but use it at night, you save 25 minus 10 cents, that is, 15 cents per kWh. A total of 150 euros.
10% Loss
But unfortunately, that’s not the whole story. The battery has to convert the AC power from the wall socket into DC power in order to store the electricity. After a while, the DC power becomes AC power once more. To do this, the battery itself consumes regarding 10% of its capacity. So instead of using 1000 kWh at night, you might use 910 kWh at home. At 25 cents per kWh, this loss would cost you 22.50 euros.
Also, I’ve noticed that in the winter, say November to February, you simply can’t get enough power from the panels to fully charge the battery. Instead of 1000 kWh of solar power you can use at night, you’re looking at 700 kWh per year.
In short: batteries this small are a good idea to take some pressure off the grid. But don’t do it for the money.
Vincent Dekker writes regarding innovations and developments in the green energy sector, both close to home and far away. For more episodes visit trouw.nl/vincentwilzon. Vincent also has a podcast, including one regarding batteries – Listen through this Link to it through known channels or search for it.
Also read:
Car batteries are a big promise, but who will deliver and when?
I wrote last week that car batteries might replace countless nuclear and natural gas power plants by 2040. There’s just one problem: The systems to make that happen have been designed, but not yet implemented. “The step from the lab to practice is a huge one.”
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