Solar Panels and Immersion Heaters Ireland 2026: How to Get Free Hot Water From Your Solar System

Heating water accounts for roughly 20% of the average Irish household’s energy bill. For most homes, that means running an immersion heater for 1–2 hours daily at a cost of €500–€800 per year. But if you already have solar panels — or you’re about to get them — a simple device called a solar PV diverter can redirect your excess solar electricity to your immersion heater, giving you free hot water for 7–9 months of the year.

This guide explains how solar PV diverters work with immersion heaters in Ireland, which brands to choose, what it costs, and whether it makes more financial sense than exporting your surplus to the grid.

How a Solar PV Diverter Works With Your Immersion

Every solar panel system generates more electricity than your home uses at certain times of day — typically late morning through early afternoon when the panels are producing at peak but nobody is home. Without a diverter, that surplus electricity gets exported to the grid. Your energy supplier pays you for it under the Clean Export Guarantee, but only at 18–21c/kWh — roughly half what you pay to buy electricity back.

A PV diverter changes this equation. Here’s the sequence:

1. A CT clamp (sensor) attaches to your meter board and monitors electricity flow in real time
2. When solar generation exceeds household consumption, the diverter detects surplus power
3. The diverter proportionally routes that surplus to your immersion heater element
4. Your hot water heats up gradually using only free solar electricity
5. If someone turns on the kettle or washing machine, the diverter instantly reduces power to the immersion so you don’t draw from the grid

The key word is proportional. Unlike a timer switch that sends 3kW to your immersion in one burst, a diverter might send 500W, then 1.2kW, then 800W — constantly adjusting to match your exact surplus. It never imports grid electricity to heat water. It only uses what would otherwise be exported.

The Financial Case: Diverter vs Export

This is the question every solar panel owner asks: should I use surplus electricity to heat water, or should I export it and take the payment?

The maths is straightforward:

What You Do With Surplus	Value per kWh	Value of 1,500 kWh Surplus/Year
Export to grid (CEG rate)	18–21c	€270–€315
Heat water (replaces grid electricity)	37–42c	€555–€630
Extra value from diverter	16–24c	€240–€360 more per year

Using surplus solar to heat water is worth roughly double what you’d earn by exporting it. A diverter costing €400–€600 installed pays for itself in 1.5–2.5 years.

Of course, you won’t divert all your surplus — once the tank is hot, the diverter has nowhere to send the extra power, and it reverts to exporting. But for the 1,000–1,500 kWh that goes to hot water each year, you’re getting nearly double the value.

How Much Hot Water Will You Actually Get?

This depends on your solar system size, the time of year, and your hot water usage. Here’s what to expect with a typical Irish 4–5 kWp system:

Month	Surplus Available	Hot Water Coverage	Need Immersion Boost?
November–January	Low (1–3 kWh/day)	20–40%	Yes — top up needed most days
February & October	Moderate (3–6 kWh/day)	50–75%	Sometimes — depends on weather
March–September	High (5–15 kWh/day)	90–100%	Rarely — free hot water most days

A family of four typically uses 3–5 kWh of electricity per day to heat water (that’s about 1–1.5 hours of immersion time). A 5 kWp system on a good April day can easily produce 8–12 kWh surplus after household use — more than enough to fully heat a 150–200 litre cylinder.

The result: most solar households with a diverter switch off their immersion timer completely from March to October. You only need to manually boost in the winter months when solar generation is low.

Best Solar PV Diverters Available in Ireland (2026)

Three diverters dominate the Irish market. Here’s how they compare:

Feature	myenergi Eddi	Solar iBoost+	BPE PV Divert
Price (unit only)	€450–€550	€300–€400	€200–€280
Installed cost	€550–€750	€400–€550	€350–€450
Dual heater output	Yes (2 loads)	No (1 load)	No (1 load)
Smart app	Yes (myenergi app)	No	No
Wi-Fi monitoring	Yes	No (display unit only)	No
Works with any inverter	Yes	Yes	Yes
Best for	Tech-savvy homeowners, dual-load setups	Budget-conscious, simple setup	Lowest cost, basic needs

Our Recommendation

The myenergi Eddi is the most popular diverter among Irish solar installers for good reason. Its dual-load capability means it can heat your immersion first, then automatically switch to a second load (like an electric towel rail or storage heater) once the tank is hot. The myenergi app shows you exactly how much energy has gone to hot water — satisfying to watch on a sunny day.

If budget is tight, the Solar iBoost+ does the core job perfectly well at €100–€200 less. You won’t get app monitoring, but you will get a display unit that shows daily and cumulative energy diverted.

For more on diverters, see our dedicated solar PV diverter guide.

Installation: What’s Involved?

Installing a PV diverter is a straightforward job for any qualified electrician — it typically takes 1–2 hours:

1. CT clamp installation: A sensor clips around your meter tails (the cables entering your consumer unit). No cutting or rewiring needed.
2. Diverter unit mounting: The diverter unit is mounted on the wall near your hot water cylinder, typically in the hot press.
3. Wiring to immersion: The diverter is wired to your existing immersion heater element. Your current timer/switch remains in place as a backup.
4. Commissioning: The electrician sets the target temperature (usually 60°C for Legionella safety) and tests the proportional control.

Important: Most solar installers will offer a diverter as an add-on when installing your panels. If you’re getting a new solar system, ask your installer to include one — it’s significantly cheaper to add during initial installation than as a retrofit.

Can You DIY a Diverter?

Technically, all three diverters come with installation manuals. However, because the CT clamp attaches near your meter board and the diverter connects to a 3kW immersion circuit, this is work that should be done by a registered electrician in Ireland. It’s a Part P electrical job. The cost of professional installation (€100–€200 labour) is not worth the risk of doing it yourself.

Diverter vs Battery: Which Is Better for Surplus Solar?

If you’re deciding how to use your excess solar generation, here’s how diverters compare to batteries:

Factor	PV Diverter	Solar Battery
Cost	€400–€750 installed	€3,500–€8,000 installed
Payback period	1.5–2.5 years	8–14 years
What it saves	Hot water costs only	All evening/night electricity
Annual savings	€250–€400	€400–€800
Lifespan	15–20+ years	10–15 years
Complexity	Very simple	Complex install

The verdict: A PV diverter is the single best-value addition to any Irish solar system. If your budget only stretches to one upgrade, get the diverter first — it pays back 5x faster than a battery. If you can afford both, the ideal setup is: diverter heats water during the day, battery stores the remaining surplus for evening use.

For a detailed battery comparison, see our guide to the best solar batteries in Ireland.

What If You Don’t Have an Immersion Heater?

Not every Irish home has a traditional immersion heater in a hot water cylinder. Here’s what to do in each scenario:

• Combi boiler (no cylinder): You don’t have a hot water storage tank, so a standard diverter won’t work. Options: add a dedicated hot water cylinder with immersion element (€800–€1,500 installed), or consider a battery instead.
• Oil/gas boiler with cylinder but no immersion element: Most older cylinders have an immersion boss (threaded fitting) that’s been blanked off. A plumber can fit an immersion element for €150–€250, then you connect the diverter.
• Heat pump system: Many heat pump setups already include a hot water cylinder with an immersion element as backup. A diverter works perfectly here — solar heats the water instead of the heat pump during sunny periods, saving wear on the heat pump and reducing electricity consumption.
• Unvented (pressurised) cylinder: These work with diverters too, but the immersion element may be lower powered (1.5–2kW instead of 3kW). This is actually fine for solar diversion since you’re rarely sending the full 3kW anyway.

Maximising Your Free Hot Water

A few practical tips to get the most from your diverter setup:

• Set your target temperature to 60°C: This is the minimum recommended to prevent Legionella bacteria growth. Some people set it higher (65–70°C) to store more thermal energy, but above 70°C you risk scalding and limescale buildup.
• Use hot water in the evening, not morning: Let the diverter heat water all day, then use it in the evening. If you shower in the morning, you’re using water heated by last night’s boost, not solar.
• Insulate your cylinder: A well-insulated cylinder (80mm jacket or factory-insulated) loses less than 1°C per hour. A poorly insulated one loses 3–5°C. That’s the difference between piping hot water at 7pm and lukewarm.
• Consider a timer for winter backup: Set your immersion timer to run for 30–45 minutes at 2am (cheapest night rate) during winter months only. The diverter handles March–October; the timer handles November–February.
• If you have a dual-load diverter (Eddi): Set Load 1 as immersion, Load 2 as an electric towel rail or storage heater. Once the tank is hot, the surplus powers the second load instead of exporting.

Real Savings: A Worked Example

Here’s what a typical Irish household can expect:

Item	Before Diverter	After Diverter
Annual hot water electricity cost	€650	€150–€200 (winter top-ups only)
Annual export income (CEG)	€250–€300	€100–€150 (less exported)
Net annual saving	—	€250–€350
Diverter cost (one-off)	—	€500–€700
Payback period	—	1.5–2.5 years

After payback, you’re saving €250–€350 every year for the remaining 15–20+ year lifespan of the device. That’s €4,000–€7,000 in lifetime savings from a €500–€700 investment.

Frequently Asked Questions

Can I add a diverter to an existing solar panel system?

Yes. A diverter can be retrofitted to any existing solar PV system regardless of brand or inverter type. The CT clamp simply attaches to your meter tails. An electrician can install it in 1–2 hours.

Does a diverter work with a heat pump?

Yes, and it’s actually an excellent combination. On sunny days, the diverter heats water using free solar electricity instead of the heat pump, reducing heat pump electricity consumption and wear.

Will a diverter void my solar panel warranty?

No. A PV diverter doesn’t connect to or modify your solar panels or inverter in any way. It only monitors electricity flow at the meter board and controls your immersion heater.

Can I use a diverter and export to the grid at the same time?

Yes. The diverter prioritises heating water. Once your cylinder reaches target temperature, any remaining surplus automatically exports to the grid as normal. You still earn Clean Export Guarantee payments — just less than without a diverter, because more of your solar energy is being used productively in the home.

How much hot water can I get for free?

With a 4–5 kWp system, expect free hot water from March to October (7–8 months). In winter, you’ll need to boost with the immersion timer or boiler. Overall, a diverter typically covers 70–80% of your annual hot water needs.

Is a diverter better than solar thermal panels for hot water?

In 2026, yes. Solar PV panels + diverter is more versatile than dedicated solar thermal panels because PV generates electricity for everything (not just hot water), and diverters are much cheaper than solar thermal collectors. Solar thermal only heats water; PV panels power your whole home and heat water as a bonus. See our PV vs solar thermal comparison for the full breakdown.