Smart Energy Management at Home: How Alexander Connects PV, Battery Storage and EVs

What happens when a PV system, battery storage, heat pump, two EVs and two wallboxes don’t simply operate alongside each other but actually communicate?

That’s exactly how things work at Alexander’s home. He has turned his house into an intelligently controlled energy system, using Loxone and Home Assistant to connect different components and control them based on the energy available.

The goal is to use as much of his own solar power as possible, distribute energy efficiently among different consumers, and keep an eye on how much electricity he draws from the grid.

We visited Alexander at home to find out how his energy management system works, why he thinks of his EV as “temporary storage,” and what he recommends to anyone looking to make their own home smarter.

What matters most to Alexander

• “I want to use as much energy from my roof as possible.”

• “For me, an EV is temporary storage. At some point, it’s going to be driven away.”

• “In winter, I keep a larger reserve in my home battery than in summer.”

• “The system decides whether available solar energy goes to the battery, hot water, the EVs, or heating.”

• “If the network goes down, the components can no longer communicate with each other.”

Before we go into more detail, let’s take a look at the components working together in Alexander’s home:

• 22.8 kWp PV system

• 22 kWh battery storage

• two electric cars

• one go-e Charger Gemini flex 22 kW

• one go-e Charger Gemini flex 2.0 22 kW

• inverters

• heat pump and hot water system

• Loxone

• Home Assistant

• other controllable consumers, such as e-bike batteries

This makes his setup much more advanced than simple PV surplus charging. Different components provide data to the system and can be controlled depending on the energy available.

For example, the charging power of the wallboxes can be adjusted. This allows the energy management system to decide when the EVs should charge and at what power.

This is where one of the advantages of an intelligent charging system becomes clear.

If the PV system is only producing a small surplus, the EV should ideally still be able to charge using the available solar energy. To make that possible, the charging power needs to be adjusted accordingly.

In Alexander’s setup, the energy management system takes care of this. If only a small amount of surplus energy is available, the system can respond accordingly and make more targeted use of it.

go-e: “Many people use a wallbox together with the go-e Controller for PV surplus charging, for example. You’ve taken your setup several steps further. How does your control system work?”

Alexander: “I have several inverters, and the wallboxes are also connected to the network. All the components communicate with the miniserver. They provide data, while commands are also sent to the wallboxes. This allows their power to be increased or reduced depending on what I need at the time.”

go-e: “So your goal isn’t just to charge your EVs intelligently, but to make your entire home more efficient?”

Alexander: “Exactly. That’s the motivation behind it.”

Smart energy management doesn’t have to end at the wallbox.

In Alexander’s home, other consumers are also integrated into the system, including the heating, hot water system, and e-bike batteries.

The heat pump is particularly interesting. When enough energy is available, Alexander can increase the heating setpoint and store additional energy in the building in the form of heat. In a way, the screed acts as thermal storage. This raises a very different question from conventional PV surplus charging: Where can the energy currently available provide the greatest benefit within the home?

And that’s where prioritising individual consumers comes into play.

Alongside his 22.8 kWp PV system, Alexander has a battery with 22 kWh of storage capacity. But when the sun is shining and energy is available, the system has to decide: where should it go?

go-e: “How do you prioritise battery storage, hot water, EVs and the other consumers?”

Alexander: “The energy manager first maintains a minimum SoC in the battery for backup power. In summer, that might be 30%, for example. In winter, I want a larger reserve, such as 50%.

Next comes hot water. The domestic hot water heat pump has a power output of 600 watts, so it needs enough time to run.

After that come the EVs. For me, an EV is temporary storage. At some point, it’s going to be driven away, and then that energy is no longer available to the house. So while the car is plugged in, I want to put as much energy into it as possible.

After that come things like increasing the heating setpoint and other consumers.”

This idea is central to Alexander’s energy strategy.

A stationary battery normally stays at home. An EV, on the other hand, might be needed and driven away at any time. So if the car is at home, plugged in, and surplus solar power is available, Alexander wants to make the most of that opportunity.

That doesn’t mean the EV always gets the highest priority, however. Instead, the energy management system considers the system as a whole and takes different requirements into account.

In simplified terms, Alexander’s priorities look like this:

1. Minimum reserve in the battery storage

2. Hot water

3. EVs

4. Heating and other consumers

This makes the wallbox part of the energy management system for the entire home.

Another important aspect of Alexander’s setup is the distinction between energy management and load management.

go-e: “How do you use your solar power for the entire house and for charging your EVs?”

Alexander: “There are two main areas in my setup. One is the energy manager. This includes things like the power requirements of individual devices and timing requirements. With hot water, for example, it matters when the hot water needs to be ready. The power of the wallboxes is also taken into account. Based on a defined order of priority, the energy manager can switch consumers on or off depending on the surplus energy available.

The second area is the load manager. It controls or limits the amount of power drawn from the grid.”

Put simply, Alexander is pursuing two goals:

Two EVs, a heat pump, a hot water system, and other household appliances can require a considerable amount of power when used simultaneously. Rather than looking at each consumer in isolation, an intelligent system can take the total load of the entire house into account.

When it comes to intelligent charging, the amount of energy currently being produced by the PV system isn’t the only useful piece of information. Another question can also be important: How full is the EV battery?

The State of Charge, or SoC, therefore also plays a role in Alexander’s system.

go-e: “You can display the State of Charge, or SoC, of your EVs in your system. How does that work?”

Alexander: “The cars are connected to the cloud. I retrieve the data from the cloud, which allows me to display the SoC. Home Assistant handles the request.

I then send the information to my miniserver via MQTT. At the moment, I use this for things including the SoC and preparing the climate control.”

For one of his vehicles, Alexander also uses the retrieved SoC to stop charging once the desired charge level has been reached. This means that information from the vehicle is incorporated into the energy management system alongside data from the house.

A 22.8 kWp PV system may sound like it produces a huge amount of solar energy. But even a large system generates considerably less electricity in winter than during the sunnier months.

go-e: “How much energy do you actually have available for charging your EVs in winter?”

Alexander: “Very little, to be honest. In December and January, I produce around 600 kWh per month. But I need that energy for heating and hot water, so there isn’t much left over. If there is anything left, of course I try to put that energy into the car or other consumers.”

That’s precisely why Alexander wants to be able to charge at low power even in winter and make use of whatever energy is actually available. If there is only a small PV surplus, his energy management system can respond accordingly.

Energy management becomes even more interesting once the sun is no longer shining. Let’s say Alexander comes home in the evening. The battery storage is charged, but the PV system is no longer producing any significant surplus. Should the car simply start charging immediately?

Not necessarily.

Alexander: “I look at the SoC of the car and try to reach my target SoC in the morning while still making the most of the potential for self-sufficiency.”

So charging isn’t determined simply by whether the vehicle is plugged in. Another important factor is when a particular charge level is actually needed.

Alexander uses two go-e Charger Gemini flex wallboxes, each with a charging capacity of 22 kW.

go-e: “Why did you choose 22 kW and, specifically, the mobile version?”

Alexander: “There was hardly any difference in price. And as an electrician, you naturally tend to go one step up. Better to have it and not need it. Flexibility was important to me because I wanted to be able to take one of the wallboxes on holiday and charge in places like Croatia or Italy. It also gives me more options. If one wallbox were ever to fail, I could simply switch things around.”

For Alexander, the wide range of interfaces was another important reason for choosing go-e. After all, with a custom-built energy management system, it’s essential that different systems can communicate with each other. He also mentions the compact design, straightforward installation, and support as reasons for his choice.

One of Alexander’s EVs is a company car that he can also use privately.

The vehicle is charged at home using one of the wallboxes. The wallbox is connected to the company via the internet, allowing the relevant charging sessions to be billed and the costs reimbursed in accordance with his arrangement with his employer.

Alexander’s charging infrastructure therefore serves several purposes at once: It forms part of his energy management system while also allowing him to bill the electricity used to charge his company car at home.

A setup involving a PV system, battery storage, several wallboxes, Loxone, and Home Assistant can seem fairly complex at first. So do you need to plan an entire smart home right from the start?

Not necessarily.

go-e: “What would you recommend to someone who wants to build a similar setup?”

Alexander: “Basically, there are two approaches. You can either use a complete system from a single manufacturer or start step by step, for example, with a wallbox and a miniserver. One thing that’s particularly important is having very stable network connections. Everything depends on the network. If the network goes down, there’s no communication either.”

This step-by-step approach is exactly what makes smart energy management interesting: the system doesn’t need to be as extensive as Alexander’s from the very beginning.

What matters more is considering how the individual components can communicate with each other when choosing them and whether the system can be expanded later.

Although numerous components are already communicating with each other, Alexander still has more ideas.

One of them may sound unusual at first: he wants to use an ultrasonic sensor to detect which EV is currently parked at the charging station. By measuring the distance, Alexander can determine which vehicle is parked there. This information could then be used for further automations.

It’s a good illustration of what Alexander’s smart home is really about: not automation for automation’s sake, but bringing together more and more information and using it to make sensible decisions for the entire energy system.