The cylinder
We establish your hot-water routine and existing heat source, then assess the cylinder, immersion and safety controls. You find out whether EDDI is a suitable addition before it appears in your quote.
FENNOR / EDDI HOT-WATER DIVERSION
From spare sunlight.
To a warmer cylinder.
Put spare solar electricity towards the hot water you use at home. Fennor helps you work out whether EDDI suits your cylinder and where it fits alongside a battery, charging or export.
HOT WATER / A DIFFERENT KIND OF STORAGE
Keep the warmth.
Understand the journey.
A cylinder stores heat. A battery stores electricity. They can work within the same home, but they do not do the same job.
Solar surplus → controlled immersion heating
Compare the other uses for surplus ↗A bright midday.
After the home’s immediate electrical demand, available surplus can be directed to a compatible immersion. EDDI modulates that heating load within the equipment and cylinder limits.
MAKE THE EXTRA EARN ITS PLACE
Hot water you use.
Surplus you actually have.
An EDDI conversation starts with how water is heated today. A household with regular cylinder demand and spare daytime generation has a different opportunity from one with no cylinder or very little surplus.
It also needs the whole energy picture. Diverting a unit of electricity means that unit cannot simultaneously charge a battery, charge the car and earn an export payment.
Already considering a heat pump? ↗THE INSTALLATION CONVERSATION
Three checks.
Before choosing the diverter.
The measurement
We identify any existing battery or smart charger and assess how the equipment measures electricity flow. Your proposal explains the compatible controls and any extra work needed to connect them.
The priorities
Together we agree whether hot water, the battery or your car takes priority. At handover, the installation team demonstrates normal operation and a grid-powered boost, including when it uses paid electricity.
One surplus.
Choose what matters.
ONE SURPLUS. DIFFERENT PRIORITIES.
Where would you
use it first?
Illustrative allocation, not a live controller or a promise of product interoperability. Fennor assesses compatibility and explains how your chosen priority would work. The installation team configures the agreed controls and demonstrates them at handover.
AFTER THE HOME’S IMMEDIATE USE3.0 kW
Available solar surplusHeat for later. Electricity, too.
In this example the immersion takes 2 kW, with 1 kW available for the battery. When the water reaches its target, priorities need to move on. Actual allocation depends on the connected controls.
The allocation totals 3 kW in every example. No energy is counted twice. Export remains another option; these examples assume the full surplus can be accepted.
YOUR PROJECT WITH FENNOR
Hot water from surplus solar.
Does it suit your home?
We explain the choices, the work involved and what happens next, so you can decide with a clearer picture.
Understand what EDDI would do.
EDDI adjusts a compatible resistive heating load to use available surplus. myenergi specifies diversion up to 3.7 kW. We explain how that differs from switching on a full-power immersion; the existing cylinder thermostats and safety controls remain essential.
We begin with your current hot water.
We ask about the cylinder, immersion and how your household uses water. The electrical assessment then establishes compatibility, grid-flow measurement and installation details. We explain the work and cable routes before you choose the accessory; a home without a cylinder is not an automatic fit.
We put the priorities in order.
We compare water-heating value with the export payment you would give up. Where you have a battery or EV, we include those needs too. Correctly coordinated controls prevent unintended battery draining, and a heat pump may heat water more efficiently than an immersion.
A SIMPLE START
Tell us about your hot water.
We will look at the options.
- 01How your household heats and uses hot water↗
- 02Cylinder and immersion details if available↗
- 03Your solar, battery and export tariff↗
MORE WAYS WE CAN HELP
Keep exploring.
SUPPORT FOR THE WORK YOU HAVE IN MIND
A clearer budget.
The support to explore.
These are the relevant funding options to discuss with Fennor alongside your project. We explain the full price, the support that may apply and the steps before you commit.
Reviewed · Guidance, not an eligibility decision.
Funding explained
EDDI & backup-switch additions
No separate listed grant
The current individual-grant list does not list a dedicated EDDI diverter or changeover-switch grant. We price these additions separately.
What this means for your project+
- Solar PV, eligible batteries and EV chargers have their own schemes; those grant amounts should not be described as funding for every accessory.
- A solar-thermal grant is for a different hot-water technology, not an EDDI. Backup operation needs compatible equipment and a safe electrical design.
Grant support
Solar thermal hot-water system
€1,200
This supports eligible solar-thermal collectors that heat water. It is not the grant for solar PV or an EDDI diverter.
Conditions & official guidance+
- Home built and occupied before 2025; system sizing, registered installation, prior-grant and approval requirements apply.
- If your interest is an EDDI connected to solar PV, we explain that different technology and its cost separately.
USEFUL ANSWERS
EDDI, explained.
Before you add it.
Plain language. No pressure to have it all figured out.
01Would EDDI make all my hot water free?
+
No. Its contribution depends on surplus, season and water use. A boost can import electricity, and power used for water cannot also be exported. We explain those trade-offs using your household’s routine.
02Can I include EDDI with a battery?
+
Potentially. We review the equipment details and explain the required compatibility and control checks. The installer then establishes the measurements and priorities; an on-screen energy flow is not a wiring design.
03Could it be added to my existing solar?
+
Often. We start with the cylinder, solar equipment and electrical installation, then explain the assessment and installation work needed for a suitable addition.
LET’S TAKE THE NEXT STEP
Talk to Fennor.
Tell us what you have in mind.
Based in Slane, serving Meath, Louth and Dublin. Tell us about a project further afield and we will confirm whether we can help.
089 403 2737 ↗info@fennor.ieWe will confirm the next step, availability and any assessment cost with you before a visit is booked.