If your solar panels generate more electricity than your home is using, that surplus doesn’t have to go to waste, or head straight back to the grid for a few pence per unit. The myenergi eddi is a solar hot water diverter designed to catch that spare energy and put it to work heating your water instead. For many UK homeowners with solar PV, it’s one of the simplest ways to get more value from a system that’s already on the roof.
This guide from Solar Maintenance And Repairs explains what the eddi is, how it works with your solar PV system, its main features, and how to set one up. We’ll also cover the basics of what can go wrong and when it’s worth calling in a professional.
What Is a myenergi Eddi?
The myenergi eddi is a solar diverter: a small device that sits between your solar PV system and your immersion heater. Its job is to detect when your panels are producing more electricity than your household is currently using, and redirect that surplus to heat water in your hot water cylinder rather than exporting it to the grid.
In practical terms, an eddi solar diverter connects your solar generation to your immersion heater and continuously monitors the balance between what your panels produce and what your home consumes. When there’s a surplus, it diverts the appropriate amount of power to the immersion element. When there isn’t, it simply steps back and lets your normal electricity supply take over.
This makes eddi particularly useful for households with a solar PV system that regularly generates more than the home uses during the day, an existing immersion heater or hot water cylinder, and a wish to reduce reliance on grid electricity for hot water. It’s also a natural fit for homes without a solar battery, or with a battery that’s already reaching capacity, since diverting surplus to hot water is another way to make use of energy that would otherwise be exported.
If any of that sounds familiar, an hot water diverter service covering eddi installation and support may be worth exploring further.
How Does the myenergi Eddi Work?
On a basic level, the eddi solar diverter follows a simple, repeating process. Solar panels generate electricity from daylight, and household appliances draw on that electricity first. Any electricity left over becomes surplus, which eddi detects in real time. Eddi then diverts the appropriate amount of that surplus to the immersion heater, which uses the power to heat the water in the hot water cylinder.
This diversion happens automatically and continuously throughout the day, adjusting as cloud cover, appliance use, and generation levels change. The result is that surplus solar generation, power that would otherwise be exported to the grid for a low rate, is converted into free hot water instead.
Because eddi works alongside your existing solar inverters and PV system rather than replacing anything, it’s typically added as a straightforward addition rather than a system overhaul.
Key myenergi Eddi Features
The eddi hot water diverter includes several features aimed toward making solar energy diversion as efficient and hands-off as possible. Fundamentally, it automatically identifies and redirects spare solar generation, managing power delivery to your existing immersion heater without any manual intervention. A boost function allows manual or scheduled heating even when there’s no surplus solar available, while app control lets you monitor and adjust settings remotely through the myenergi app. Energy monitoring shows how much surplus energy has been diverted over time, and wireless CT monitoring tracks household consumption without the need for complex additional wiring. Where extended monitoring is needed, harvi integration extends this to other circuits or appliances, and the whole system is designed with ecosystem compatibility in mind, working alongside other myenergi products such as Zappi.
These features work together, rather than in isolation: the CT monitoring feeds data to the diversion logic, which is then displayed and adjustable through the app.
What Is the harvi Wireless CT Sensor?
The harvi wireless CT sensor is a small monitoring device that measures the electrical current flowing through a circuit, most commonly your solar generation and your household consumption. “CT” stands for current transformer, and in plain terms, a CT sensor clips around a cable and measures how much electricity is passing through it, without needing to be wired directly into the circuit.
What makes harvi useful is that it communicates wirelessly with eddi, sending real-time readings so the diverter always has an accurate picture of how much surplus solar energy is available. Because it’s wireless, it can often be fitted without extensive additional cabling, which keeps installation more straightforward.
Accurate monitoring matters because eddi’s diversion decisions rely entirely on the data it receives. If CT readings are inaccurate, something covered in more detail below, the amount of energy diverted to your hot water can be affected.
Using the myenergi Eddi App
The myenergi app is the main way most homeowners interact with their eddi day to day. Through the app, you can typically monitor real-time energy generation, consumption, and diversion, check eddi’s current status and boost activity, and trigger a manual boost or set up boost scheduling to suit your household’s routine. It also lets you review historical energy information, such as how much has been diverted over a day, week, or month, check connectivity between eddi, harvi, and your home network, and receive and apply firmware updates when they become available.
For homeowners who like to keep an eye on their system’s performance, the app turns what would otherwise be an invisible background process into something visible and adjustable. It’s also usually the first place to check if something seems off with your eddi; status indicators and connectivity information are displayed clearly within the my energy eddi dashboard.
How to Set Up a myenergi Eddi
Setting up an eddi generally involves two distinct types of work, and it’s important to be clear about the difference between them.
Electrical installation requiring a suitably qualified professional covers connecting eddi to your immersion heater circuit, wiring in CT sensors where required, and integrating the unit safely into your existing electrical setup. This work should always be carried out by a qualified electrician or solar installer, in line with UK wiring regulations. We won’t cover the specifics of this wiring here, as it needs to be assessed and carried out on-site by a professional.
User configuration, by contrast, is usually something homeowners can manage themselves once installation is complete. This typically involves pairing eddi with the myenergi app and connecting it to your home Wi-Fi network, configuring or confirming harvi setup if you’re using one, setting initial boost preferences and schedules, and testing that diversion is working correctly during a sunny period.
If you’d like detailed wiring diagrams or configuration references, the myenergi eddi manual (available from myenergi directly) is the authoritative source, and it’s worth keeping a copy for future reference alongside any documentation your installer provides.
What Is the Eddi Boost Function?
The boost function on an eddi is designed for situations where you want hot water sooner than solar surplus alone would provide it, for example on a cloudy day, or ahead of a period when you know hot water demand will be higher.
There are two main ways to use it. A manual boost lets you trigger heating on demand, typically via the app or a physical button, for a set period. A scheduled boost, on the other hand, lets you set specific times, first thing in the morning for example, when eddi will heat water regardless of available solar surplus.
It’s worth understanding that boost mode can draw on grid electricity when there isn’t enough solar surplus available, since its purpose is to guarantee hot water rather than to guarantee free energy use. Used sparingly, it’s a helpful safety net; used constantly, it reduces the cost benefit that a solar diverter is meant to provide.
Can Eddi Work With a Zappi EV Charger?
Eddi is part of the wider myenergi ecosystem, which also includes the Zappi EV charger and the harvi CT sensor. Together, these devices are designed to share energy data and work from the same underlying principle: making the best use of solar generation across your home.
In a household with both eddi and Zappi installed, surplus solar energy can, depending on your priorities, be directed toward EV charging, hot water heating, or a combination of both, managed through the myenergi app. This is a genuine benefit for households investing more broadly in electrification, though it’s worth being cautious about assuming every combination or configuration will suit your specific setup; ecosystem compatibility is a feature worth discussing directly with an installer based on your actual equipment and energy goals.
If you’re also considering how solar-generated energy is stored rather than immediately used, it’s worth exploring solar battery storage as a complementary, rather than competing, technology to diversion.
Common myenergi Eddi Problems
Most eddi issues fall into a handful of recognisable categories. Understanding the basics can help you judge if something is a quick check or something that needs professional attention.
Eddi not working or no surplus being diverted. This is often connected to CT sensor placement or calibration, a change in your solar generation pattern, or an app connectivity issue rather than a fault with the eddi unit itself. Confirming that your solar system is generating normally, and that the app shows a live connection, is a sensible first step.
App connectivity issues. If the myenergi app isn’t showing current data, it’s often a Wi-Fi or network problem rather than a hardware fault. Restarting your router, checking your home network, and confirming eddi appears as connected in the app can resolve many of these cases.
Firmware and communication faults. Occasionally, a firmware update can resolve unexpected behaviour, and the app will usually flag when an update is available.
Why is my eddi not working: the flashing red light. A flashing red light on eddi generally indicates a fault condition that the unit has detected, rather than normal operation. The exact meaning varies depending on the pattern, and myenergi’s own documentation is the definitive reference for interpreting specific light sequences.
How do I reset my eddi. A basic reset, typically achieved via the app or a power cycle depending on your model and firmware version, resolves many temporary glitches, particularly connectivity or display issues. If a reset doesn’t resolve the problem, or the same fault returns quickly, that’s usually a sign of something that needs a closer look.
Can I fix my eddi myself. Basic checks, confirming Wi-Fi connectivity, checking the app, and power-cycling the unit, are reasonable for most homeowners to attempt. However, we don’t recommend opening, rewiring, or attempting to repair the internal electrical components of eddi yourself. This is specialist electrical work, and incorrect handling carries a genuine safety risk.
This article only scratches the surface of Eddi fault-finding; a full troubleshooting walkthrough will be published as a dedicated guide covering diagnostic checks in more depth. In the meantime, our solar inverter troubleshooting guide covers a similar diagnostic approach for the inverter side of your system, and our solar PV service and repairs team can assist with wider system issues connected to your Eddi setup.
When Should You Book an Eddi Diagnostic?
Basic checks are a sensible first step, but there are situations where booking professional myenergi Eddi diagnostics and repair makes more sense than continuing to troubleshoot on your own. Persistent fault indicators that don’t clear after a reset, repeated communication problems between eddi, harvi, and the app, or suspected hardware faults such as the unit failing to power on are all worth a professional look. The same goes for any electrical issue, burning smells, unusual noises, or visible damage, as well as repeated shutdowns during otherwise normal operation, or fault codes and light patterns you can’t identify with confidence.
How Much Does Eddi Installation Cost?
Eddi installation cost varies from property to property, and we’d rather explain what drives that variation than quote a figure that won’t hold true for every home. Your existing solar PV setup plays a part: how reliably your system is already generating, and how much additional configuration is needed to integrate eddi, both affect the scope of the job. The layout of your consumer unit and immersion circuit affects how straightforward the electrical work is, and older or non-standard immersion heaters may need additional attention to work well with the new diverter. The distance between your consumer unit, eddi, and the immersion heater has a bearing on labour and materials too, as does the choice between wiring CT sensors in directly or using a wireless harvi setup, and if extended monitoring is needed, additional harvi units add to the overall package. Any wider electrical upgrades needed to bring existing wiring up to standard will also factor in, and, more generally, properties with straightforward access and modern wiring are typically quicker and more cost-effective to work on than those requiring extensive additional work.
Because these factors differ so much between properties, the most reliable way to understand your own eddi installation cost is a property-specific assessment. A more complete breakdown of installation costs and pricing factors is planned as a dedicated follow-up article. In the meantime, our solar diverter installation page outlines the installation process and model options, including the eddi, in more detail.
Is a myenergi Eddi Right for Your Solar PV System?
An eddi hot water diverter tends to suit households that already generate solar surplus regularly, have a hot water cylinder and immersion heater in place, and want a low-maintenance way to put spare solar energy to use rather than exporting it. It’s a particularly good fit if you’re also interested in the wider myenergi ecosystem, including Zappi EV charging, since the app-based monitoring and control extend naturally across all three devices.
That said, an eddi isn’t automatically the right choice for every property. Homes with limited solar surplus, no immersion heater, or hot water needs that don’t align well with daytime generation may see more limited benefit. A professional assessment of your solar generation patterns and hot water usage is the most reliable way to judge if eddi, or an alternative diverter, is the better fit.
