You come home after a day at work, plug your electric car into the charging station, and the next morning the battery is fully charged again. This is the daily reality for many EV drivers. But when you charge your car in the evening, you often pay top dollar for electricity from the grid—especially once the sun has set and your solar panels are no longer generating power. With a smartly connecting a home battery to your charging station, you can charge your car using your own free solar energy or inexpensive off-peak electricity.
Want to find out right away which system is right for your situation? Request personalized advice from our specialists now or stop by our showroom in Vught for a demonstration.
How a home battery works as a buffer for your charging station
Instead of feeding electricity directly back into the grid for a low rate, a home battery stores the excess energy from your solar panels . Technically speaking, we’re talking about a modular storage system—often based on safe and sustainable LiFePO4 (lithium iron phosphate) cells—that’s connected to a smart inverter.
To ensure this system works safely and efficiently with your charging station, a built-in Energy Management System (EMS)—the smart traffic controller in your meter cabinet—manages energy flows through two key functions:
- Smart Power Distribution: The EMS continuously measures how much power your solar panels generate and how much your home consumes. As soon as there is excess solar power, the system immediately directs it to the home battery or your car, rather than letting it be sold back to the grid at a low rate.
- Peak shaving (prevent overloading): A charging station draws a huge amount of power in a short period of time (often 3.7 kW to 11 kW). If you’re cooking or doing laundry at the same time, your power grid can become overloaded. At such times, the home battery immediately steps in to absorb this “peak.” This means you don’t have to upgrade your grid connection with the utility company, saving you hundreds of euros per year in standing charges.
Charging your car with a home battery
Charging an electric car requires a lot of power. An average EV battery has a capacity of 40 to 100 kWh, while a standard home battery often has a capacity between 5 kWh and 20 kWh. To ensure these work together efficiently, the system follows a logical step-by-step plan:
1. Determine the power source
You choose how the home battery is powered. This can be done via your own solar panels during the day, or via the power grid at times when rates are low or even negative.
2. Regulate charging
The EMS detects when the car is connected and regulates the power supply. This prevents the home battery from being drained uncontrollably by the car all at once.
3. Schedule the charging time
Using an app, you can set the car to prioritize using the stored solar power from the home battery as soon as the sun goes down.
Requirements and Technical Choices
If you want to charge an electric car efficiently using a home battery, the technical settings play a major role. There are two ways to connect a home battery:
- AC-connected system: The battery is connected to your home’s alternating current (AC) grid. This is ideal for existing solar panel systems, as the battery can be installed flexibly. However, a small conversion loss occurs when charging the car (from DC to AC and back to DC in the car).
- DC-connected system: The battery is connected directly to the solar panels’ inverter before the electricity is converted to alternating current. This is technically more efficient.
To charge an electric car, a home battery with a capacity of 20 kWh or more is recommended if you want to charge a substantial number of kilometers using your own storage. Smaller batteries run out faster, but can still be very useful for handling the initial peak of the charging process.
How much does a home battery cost, and what are the benefits?
The cost of a home battery depends largely on its capacity and power output. A high-quality home battery starts at a few thousand euros for plug-in systems and increases as the storage capacity grows.
Return on Investment and Savings
The financial benefit lies in maximizing your own consumption of solar power. As the net metering policy gradually changes, feeding excess power back into the grid yields fewer and fewer returns. By storing this electricity in your car via your home battery, you avoid having to purchase expensive grid power.
With a dynamic contract, you can charge your home battery cheaply from the grid during off-peak hours (for example, when there’s plenty of wind at night), and then use that electricity to charge your car during the day or during the evening peak. This way, you’ll recoup your investment faster.
Frequently Asked Questions About Charging Your Car with a Home Battery
How many kWh do I need to charge an electric car using a home battery?
An average car battery has a capacity of 40 to 100 kWh, while a home battery typically ranges from 5 to 20 kWh. So you’ll rarely be able to fully charge your car with it. Think of it mainly as a smart buffer: with a 10 kWh battery, you can easily add 50 to 60 kilometers to your range. This is often more than enough for your daily commute. Do you want to consistently charge more kilometers from your own storage? Then opt for a system of 20 kWh or more.
Do I need to modify my charging station to work with a home battery?
No, in most cases you don’t need to modify your charging station. The integration is fully managed in the meter cabinet by the energy management system (EMS). This system ensures that the home battery and the charging station communicate seamlessly with each other, regulates the power supply, and automatically manages functions such as peak shaving.
How much will this save me on my monthly energy bill?
The exact savings depend on your solar panels, driving habits, and energy contract. With the elimination of the net metering program, storing and using solar power immediately saves you money. If you combine this with a dynamic energy contract—where you charge during the cheapest hours—the savings can quickly add up to several dozen euros per month.
Can I still use the battery when the sun isn’t shining in the winter?
Yes, that’s exactly when a home battery comes in handy. In the winter, you don’t charge the battery with solar power, but through the power grid. Do you have a dynamic contract? If so, the battery automatically charges itself at night when electricity rates are lowest (for example, when the wind is blowing hard). You can then use that cheap electricity to charge your car cost-effectively during the day.
Contact and Professional Assistance
Do you want to ensure that your energy system continues to perform optimally and safely for decades to come? Off Grid Power Station is the specialist in energy storage. As the market leader in plug-in home batteries, we have already successfully helped more than 10,000 customers find the right energy solution. It’s no coincidence that our customers rate our expertise and service a 9.1 (based on over 1,900 reviews).
You’re more than welcome to visit our showroom in Vught for a personalized demonstration and tailored advice from our experts. Contact us today contact us today or request a no-obligation quote right away.