Quick Answer
A virtual battery stores export credits on your electricity bill. The optimal configuration depends on your actual consumption, roof orientation, battery needs, and choosing the right export tariff.
What is a physical solar battery?
A physical solar battery is chemical storage hardware (usually lithium iron phosphate or LiFePO4) installed inside your home or garage. When your solar panels generate more electricity than your household is using during the day, the surplus is routed into the battery to charge it.
In the evening and overnight, when solar generation stops, your home automatically draws power from the battery instead of importing electricity from the grid. This maximizes your self-consumption, but it requires a substantial upfront capital investment.
What is a virtual battery?
A virtual battery (often called a “solar wallet” or “batería virtual”) is not a physical device. It is a financial billing agreement offered by certain electricity supplier companies (comercializadoras) in Spain.
Instead of storing actual electricity, your exported solar energy is converted into a cash balance (in euros) based on the supplier’s export compensation rate. This credit accumulates in a virtual account and is used to offset future electricity bills, including fixed standing charges (potencia and taxes), potentially reducing your bill to €0. Note that some suppliers charge maintenance fees or require specific tariff subscriptions for this service.
Main differences at a glance
Here is a comparison between physical and virtual batteries:
| Feature | Physical Battery | Virtual Battery Tariff |
|---|---|---|
| Hardware Required | Yes (Lithium battery and hybrid inverter) | No (Financial billing arrangement only) |
| Upfront Cost | High (€3,500 to €6,500+) | Zero upfront (Tariff-dependent fees may apply) |
| Backup During Outages | Yes (Only if backup box and hybrid inverter installed) | No (Grid connection goes down, you lose power) |
| Reduction of Bill Standby Charges | No (Only offsets energy charges) | Yes (Can offset fixed power charges and taxes) |
| Portability | Stays at property unless uninstalled | Lost or reset if you switch supplier |
Backup power: the biggest misunderstanding
The most common misconception is that having any battery guarantees power during a blackout. By default, grid-tied batteries shut down immediately during grid failures to protect utility workers. If you need backup power, you must explicitly request your installer configure an automatic transfer switch or backup box. A virtual battery cannot provide any form of electrical backup.
Can you use both?
Yes. A highly efficient setup combines a physical battery sized to cover your normal overnight usage (e.g., 5kWh or 10kWh) with a virtual battery tariff. The physical battery minimizes your evening imports, while the virtual battery accumulates excess credits from your large daytime generation surpluses to reduce your winter standing charges to zero.
For electricity tariff switching and post-install bill optimisation, we work alongside weSwitchSpain to find the best virtual battery conditions.