Stuurbox or EMS API: What Do You Need for Smart Energy Management?
Published by
Teun van Sinten
Covolt Netherlands
You want to get more out of your solar panels, battery, or charging infrastructure. You’ve heard about Covolt and you’re excited, but then the practical question arises: Do I need to replace my existing control box, or can I just connect it?
The answer depends on what you already have. And the good news is: in most cases, you won’t need to replace anything. Covolt offers two options. In this article, we’ll explain the difference—without the jargon—so you’ll know exactly which one is right for your situation.
Covolt now manages more than 900 installations in the Netherlands and Belgium. The question “control box or EMS API?” is one of the most frequently asked questions at the start of a partnership. So by now, we know the answer well.
First, let's understand: what does a steering box actually do?
A control box is a local hardware device located at your energy installation. The box communicates in real time with your inverters, batteries, power meters, and charging stations, and executes control commands based on signals from a central platform such as Covolt Horizon.
Without a control box, there is no local control. That means: no automatic response to negative energy prices, no optimization of self-consumption, and no real-time adjustments during grid congestion.
The control box is, therefore, the link between the cloud-based intelligence and your physical on-site installation. Covolt Horizon thinks; the control box acts.
The Covolt Horizon Control Box
The Covolt Horizon Control Box is proprietary hardware developed by Covolt. We install it on-site at your facility. Using its own 4G connection with a dedicated SIM card, the Control Box serves as a fast and secure bridge between your facility and the Covolt Horizon platform.
The main advantage of the Control Box is its local response speed. Even if the internet connection at the site is lost, the Control Box continues to function, and local control remains possible. For installations where every second counts—such as during aFRR activations or curtailment due to negative prices—this makes a real difference.
The right choice if
- You don't have a control box installed yet
- You're starting up a new installation
- You want to achieve maximum response speed through local control
- You want a reliable connection that is independent of the local network
Covolt handles the entire installation and commissioning process on-site. Once the system is connected, Covolt takes full responsibility for its operation and monitoring.
The Covolt Horizon EMS API
The EMS API is not hardware but a software interface. If you already have a control box from another brand—such as Envitron, Embion, or With the Grid—you can connect directly to the Covolt Horizon platform via the EMS API.
Your existing control box stays in place. Covolt sends all control commands to your hardware via the API. You keep your own system; Covolt provides the intelligence: market optimization, power control, and predictive algorithms.
The right choice if
- You already have a steering box from another brand
- You don't want to or don't need to replace your existing hardware
- You'll want to take advantage of Covolt's market optimization and energy trading
The EMS API does not require on-site installation. Covolt handles the technical integration remotely.
What's the difference? — At a glance
| Covolt Control Box | EMS API | |
|---|---|---|
| Hardware Required | Covolt installs on-site | No replacement |
| Connection | 4G SIM card — independent | Via an existing connection |
| Response time | Real-time, local | Via the cloud |
| Existing control box | Replacement or new | Remains unchanged |
| Brands | Covolt's own hardware | including Envitron, With the Grid, Embion, among others |
| Installation | On-site by Covolt | Remotely by Covolt |
| Market Access | Entirely through Covolt Horizon | Entirely through Covolt Horizon |
No matter which option you choose, the Covolt Horizon platform offers the same capabilities in both cases: automated trading on the day-ahead market and the imbalance market, participation in aFRR and congestion management via GOPACS, real-time monitoring via the myHorizon app, and monthly reports.
How do you know what's right for you?
Decision Aid
Do you already have a control box on your system?
This is the most crucial question. In most cases, the choice follows directly from this.
Question 2 of 3
Do you actively participate in aFRR or other fast balancing markets?
With aFRR, your system must respond within 30 seconds. Local control via the Control Box offers an advantage over cloud-based control in this regard.
Question 2 of 3
Would you like us to take care of everything for you, including on-site installation?
The Control Box is a complete solution: Covolt supplies the hardware, installs it, and then takes over all control and monitoring.
Your recommendation
The Covolt Horizon EMS API is the best fit for your situation.
Your existing control box stays in place. Covolt connects via the API and provides market optimization and power control—without any new hardware.
Covolt checks in advance whether your current system is technically compatible. We handle the integration remotely—no on-site installer is needed.
Your recommendation
The Covolt Horizon Control Box is the best fit for your situation.
Covolt installs the hardware on-site and then takes over all control and monitoring. You don't have to do anything yourself.
The Control Box operates via its own 4G connection with its own SIM card—completely independent of the local network at your location.
Your recommendation
Consider the Control Box as an upgrade.
You already have a control box, but for aFRR and other fast-responding markets, local control offers a tangible advantage in terms of response speed.
During a consultation, Covolt will discuss whether switching to the Control Box makes sense for your specific installation. There’s no obligation.
More charging stations. Without a more expensive connection.
In a single consultation, Covolt will determine how many charging stations your installation can handle and what benefits smart control can provide.
Frequently Asked Questions About Charging Stations and Grid Congestion
What is the difference between the Covolt Control Box and the EMS API?
The Control Box is proprietary Covolt hardware that is installed on-site at your facility and connects to the platform via 4G. The EMS API is a software interface that allows you to connect your existing control box from another brand to Covolt Horizon without replacing any hardware.
Will the EMS API work with my current control box?
Yes. Covolt connects to control boxes from Envitron, With the Grid, Embion, and others via the EMS API. Please schedule a consultation to find out if your specific make and model are compatible.
Does Covolt need to come on-site for the EMS API?
No. For the EMS API, Covolt handles the technical integration remotely. For the Control Box, however, Covolt does handle the on-site installation.
Can I switch from the EMS API to the Control Box later?
Yes. If you decide later that you want to switch to the Covolt Control Box—for example, to improve local response speed—that’s possible. Covolt will discuss this during the consultation.
