Smart Use of Photovoltaic Surplus Power: How to Get More from Your Energy!
More and more households and businesses are turning to photovoltaic systems — and for good reason: solar power is clean, free, and a true long-term investment in the future. But what do you do when your PV system generates more electricity than you currently need?
This so-called surplus energy is not waste — on the contrary: it’s worth its weight in gold. In this blog, we’ll show you smart ways to use your surplus electricity sustainably and profitably — from classic feed-in to innovative ideas like the 21energy Bitcoin Heater.
1.Store electricity with solar batteries
The most straightforward solution: store the surplus in a home battery. This way, you can use it when the sun isn’t shining — for example, in the evening or at night. Intelligent systems ensure you optimize electricity consumption and maximize battery life.
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Advantage: Maximum self-consumption, less dependency on the grid.
- Example: Your washing machine runs in the evening with solar power generated during the day.
2.Feed into the public electricity grid
You can also feed your surplus electricity into the grid and receive a feed-in tariff. The amount depends on your country, provider, and tariff — but in Austria currently usually between 7 and 10 cents per kWh.
Example: A company feeds in 3,000 kWh per year and receives about €240 in return.
3.Smart home: automatically control household appliances
When your PV system produces electricity, your devices should use it directly. Smart systems like energy managers or intelligent sockets detect surplus and, for example, automatically start the dishwasher or heat pump.
Example: Your dishwasher starts at midday when the sun is at its peak.
4.Bitcoin Mining & Heating with 21energy
Innovative and doubly clever: the 21energy Ofen Pro not only converts surplus solar power into heat — it also mines Bitcoin. This way, you heat CO₂-neutrally and generate additional income.
Calculation example:
– 3,000 kWh fed in: €240 revenue
– 3,000 kWh via 21energy: €864 in BTC
→ Almost three times the value!
Calculate your annual heating savings
5.Hot water preparation
Surplus electricity can also be used for hot water — e.g., via a heating element in the boiler. This covers part of your heat demand with solar power and reduces gas or grid electricity consumption.
Example: Your shower water was heated free by the sun during the day.
6.Charging e-cars & e-bikes
Ideal for anyone with electric mobility: use surplus solar power to charge your e-car or e-bike. Many wallboxes can be operated directly with PV power — saving money and being particularly sustainable.
Example: You charge your car free during the day — and drive emissions-free.
7.Power-to-X: future technologies
Surplus electricity can also be used to produce hydrogen or synthetic fuels. These so-called Power-to-X technologies are still in development but offer great potential.
Example: A farm produces hydrogen for its tractors — completely emission-free.
Conclusion
|
Method |
Advantages |
Example |
|
Solar battery |
Maximize self-consumption, grid independence |
Run appliances in the evening with stored solar energy |
|
Feed-in to the grid |
Feed-in tariff, simple implementation |
Company feeds 3,000 kWh → approx. €240/year |
|
Smart household control |
Devices use electricity exactly when it’s available |
Washing machine starts automatically at midday with high PV output |
|
21energy Bitcoin-Heater |
Use electricity for heating & earn BTC (up to 3× higher value) |
3,000 kWh → €864 equivalent in Bitcoin + heating |
|
Hot water preparation |
Saves fossil energy, easy integration |
Heating element in boiler heats shower water with solar power |
|
E-car / e-bike charging |
Directly increase self-consumption, CO₂-free driving |
Charge car with solar power during the day → no extra electricity costs |
|
Power-to-X (e.g. hydrogen) |
Future technology, versatile as storage or fuel |
Farm produces hydrogen for own flee |
Ofen 2 in a nutshell
Ofen 2
(1-year average)
As of 06.2025
(4-year average)
As of 06.2025
Conclusion: Your electricity is worth more than you think
Whether storing, heating, charging, or even earning money through Bitcoin mining — your photovoltaic surplus electricity is a valuable resource. Those who use it smartly not only reduce their electricity bills but actively contribute to the energy transition.
At 21energy, we show you how to get more out of your electricity. Our tip: Use the Ofen Pro, combine heat with income — and turn solar energy into real value creation.
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