Solar Panels and Immersion Heaters in Ireland: How to Get Free Hot Water from Your Panels

A solar immersion diverter costs €450–€640 installed and gives you free hot water from March to October. Here is how it works, which brands to consider, and whether it is worth it for your home.

If you already have solar panels — or you are about to get them — there is a simple add-on that most installers will recommend: a solar immersion diverter. It sends your surplus solar electricity to your immersion heater instead of exporting it to the grid, giving you free hot water whenever the sun shines.

It is one of the fastest-payback upgrades in the entire home energy space. For €450–€640 installed, you can save €350–€600 per year on hot water. That is a payback period of 1–2 years — far faster than a battery or even the solar panels themselves.

This guide explains exactly how solar immersion diverters work, compares the leading brands available in Ireland, and helps you decide whether to add one to your solar setup.

How a Solar Immersion Diverter Works

The concept is straightforward:

1. Your solar panels generate electricity during the day.
2. Your home uses what it needs for lights, appliances, and so on.
3. Any surplus electricity would normally flow back to the grid, earning you about 24c/kWh under the Clean Export Guarantee.
4. The diverter detects this surplus in real time and redirects it to your immersion heater element instead.
5. Your water heats up gradually throughout the day, using power that would otherwise have been exported.

Unlike solar thermal panels (which heat water directly using the sun’s heat), a PV diverter uses your existing solar PV electricity to power the immersion heating element in your hot water cylinder. You do not need any new plumbing — just an electrical connection between the diverter unit and your existing immersion heater.

Is a Solar Immersion Diverter Worth It?

Let us run the numbers for a typical Irish household with a 4.4 kWp solar system (10 panels):

Scenario	Without Diverter	With Diverter
Surplus exported to grid	2,400 kWh/yr	1,200 kWh/yr
Export income (@ 24c/kWh)	€576	€288
Hot water cost (gas/electric)	€500–€700/yr	€150–€250/yr
Hot water savings from diverter	—	€350–€450/yr
Net benefit of diverter	—	€62–€162/yr better off

Why it works: You lose €288 in export income (because you are diverting 1,200 kWh to the immersion instead of the grid), but you save €350–€450 on hot water heating. The net gain is €62–€162 per year — and the diverter pays for itself in under 2 years.

The bigger your household, the more you save. A family of 4–5 uses more hot water and gets more value from the diverted electricity. Households that currently heat water with an electric immersion (rather than gas) see even larger savings because they are replacing 38c/kWh electricity with free solar power.

Best Solar Immersion Diverters in Ireland (2026)

Three brands dominate the Irish market. Here is how they compare:

Feature	myenergi Eddi	Solar iBoost+	BPE PV Divert
Price (unit only)	€400–€500	€300–€400	€250–€350
Installation cost	€100–€150	€100–€150	€100–€150
Smartphone app	Yes (myenergi app)	No	No
Works with batteries	Yes — prioritise battery or tank	Limited	No
Works with heat pumps	Yes	No	No
Dual load support	Yes (immersion + heater)	No	No
Best for	Future-proof setups	Simple, reliable installs	Budget-conscious buyers

Our Pick: myenergi Eddi

The myenergi Eddi is the most popular diverter in Ireland for good reason. It is the most intelligent of the three — it works alongside a solar battery, letting you decide whether surplus power goes to the battery or the hot water tank first. It also works with heat pumps, which the iBoost cannot do. The smartphone app lets you monitor exactly how much free hot water you are generating.

If you want the simplest, cheapest option and do not plan to add a battery or heat pump, the iBoost+ is a solid, reliable choice that has been on the Irish market for years.

Seasonal Performance: When Does It Heat Your Water?

Solar immersion diverters are not a year-round replacement for your boiler — but they cover more of the year than you might expect:

Season	Months	Hot Water from Solar	Boiler Backup Needed?
Summer	May–Aug	80–100%	Rarely
Spring / Autumn	Mar–Apr, Sep–Oct	50–80%	Some days
Winter	Nov–Feb	10–30%	Yes — most days

In practical terms, you can turn off your boiler for hot water from May to August in most years. During spring and autumn, the diverter will pre-heat the water to lukewarm, and your boiler only needs to top it up — using far less gas or oil. In winter, you still get some contribution on bright days, but you will rely on your boiler or immersion for most hot water.

Over a full year, a well-sized system typically provides 60–70% of a household’s hot water needs for free.

Do You Need a Solar Immersion Diverter?

A diverter makes sense if you tick any two of these boxes:

• You have (or are getting) solar panels of 3 kWp or larger
• Your home has a hot water cylinder with an immersion heater element
• You are not home during the day to use surplus electricity as it is generated
• You do not have a solar battery (or do not plan to get one soon)
• Your hot water is currently heated by oil, gas, or peak-rate electricity

A diverter is less useful if:

• You have a combi boiler with no hot water cylinder (no immersion to divert to)
• You already have a large solar battery that absorbs most of your surplus
• You use very little hot water (single-person household)

Diverter vs Battery: Which Should You Get First?

This is one of the most common questions from Irish solar owners. Here is a quick comparison:

	Solar Diverter	Solar Battery (5 kWh)
Installed cost	€450–€640	€2,500–€3,500
Annual savings	€350–€600	€250–€400
Payback period	1–2 years	7–10 years
Lifespan	15–20 years	10–15 years
What it does	Heats water with surplus	Stores electricity for evening use

Our recommendation: If you are on a budget, get the diverter first. It has a far better return on investment and starts saving you money almost immediately. You can always add a battery later — and if you choose the myenergi Eddi, it will integrate with a battery when you add one.

Installation: What’s Involved?

Installing a solar immersion diverter is a straightforward job for a qualified electrician. Here is what happens:

1. CT clamp fitted — A small sensor (current transformer) clips around your main electricity supply cable. This is how the diverter detects surplus power.
2. Diverter unit mounted — The unit is wall-mounted near your consumer unit (fuse board), usually in the utility room or wherever your hot water cylinder is.
3. Wired to immersion — The diverter is connected to your existing immersion heater element. No plumbing changes needed.
4. Commissioned and tested — The electrician tests that the diverter correctly detects surplus and diverts the right amount of power.

The whole job typically takes 1–2 hours. If you are having solar panels installed at the same time, most installers will fit the diverter as part of the same visit for a reduced labour cost.

Important: You need a hot water cylinder with an immersion heater element. If your home has a combi boiler (which heats water on demand with no cylinder), a diverter will not work. Most Irish homes built before 2010 have a cylinder; newer homes may or may not, depending on the heating system.

Common Questions

The Bottom Line

A solar immersion diverter is the single best-value add-on for a solar PV system in Ireland. The maths is simple:

• €450–€640 installed — less than a weekend away
• €350–€600 saved per year on hot water bills
• 1–2 year payback — then free hot water for 15–20 years
• Free hot water from March to October in most households
• No plumbing changes — just a 1–2 hour electrical installation

If you are getting solar panels, ask your installer to include a diverter in the package. If you already have panels, a diverter is the cheapest way to extract more value from your investment. Either way, get a free quote to find out exactly what you could save.