ᐅ Is it not possible to operate a photovoltaic system with battery completely off-grid?

Hello everyone,

Until recently, I believed that with a photovoltaic system on the roof and an appropriate battery, you could achieve a certain level of independence from the public power grid. My understanding was that

• the photovoltaic system charges the battery,
• the electricity for all devices in the house comes from the battery,
• and the battery is connected to the public grid to feed in excess electricity or to recharge when there is little sunlight.

Recently, I heard from acquaintances that it is unfortunately not possible to use a photovoltaic system with a battery in this way. Although the battery is charged by the photovoltaic system, if I want to use electricity, I still have to take it from the public grid. At the same time, electricity from the battery is fed into the public grid, but I remain fully dependent on the energy provider.

Is this really the case? That would be completely absurd. Does this mean that despite having a full battery, I will still experience any power outage (which, strangely, happens at least once a year here)?

No, the household users already consume electricity from the battery.
However, a grid connection is still necessary because the battery is not large enough, and in winter, the photovoltaic system produces too little. During winter, the battery simply sits empty and even requires maintenance charging from the public power grid.

Hmm, so it is just as I thought? Strange, supposedly the energy consultant from the utility company told my acquaintance that this wouldn’t be possible...

Reason: full quote removed

Theoretically, yes. But you would need a system that can generate enough energy during winter and on several days with little sunlight to cover multiple days’ consumption. Such a large system usually cannot fit on a single-family house roof. Additionally, the battery would need to compensate not only for evenings and nights but also for days with low energy production. Economically, it doesn’t make sense.

PS: Charging the battery from the public grid is doubly pointless. In that case, you pay for the electricity plus conversion losses, storage losses, and battery wear. This easily makes the cost per kWh more than twice as high.

In many systems, the public grid is required for the battery and photovoltaic system to function properly.

The grid controls the oscillation. Without power from the grid, there is no power from the photovoltaic system or the battery.

However, there are also technologies that can provide power temporarily during a blackout (as long as the sun is shining or the battery still has charge).

That's right. Many systems cannot operate independently from the grid simply because they cannot provide the necessary high short-circuit currents in the event of a fault.