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Solar Diverter Payback Calculator (Ireland)
A solar diverter sends surplus solar into your immersion instead of the grid, heating your water for free. But the Clean Export Guarantee changed the sum: now a diverter only pays if the water heating it displaces costs more per unit than you’d earn exporting that same surplus. This calculator gives you the honest answer for your setup — including when the answer is “just keep exporting”.
Reviewed 23 juil. 2026
The tool
Open the tool full-screen ↗Use it right here — nothing is saved, and there’s no sign-up.
This tool may link to relevant products and services to keep it free. Affiliate links are marked and are placeholders during this early phase — see our affiliate disclosure
What to know
The logic is simple once you see it. Every kilowatt-hour of surplus solar is worth either your export rate (if you sell it) or the cost of the water heating it replaces (if you divert it). If you currently heat water with an electric immersion at the day rate, diverting almost always wins. If you heat water cheaply — gas, a heat pump, or a night-rate immersion — the export rate can be worth more, and a diverter may never pay back.
That is why a diverter is one of the few solar add-ons where the honest answer is genuinely “it depends”. This tool refuses to fake a saving: it compares your real displacement cost against your real export rate and tells you the truth, then points you to a battery sizer if storing the surplus would beat both.
How this tool works
No sign-up, nothing saved — here is what it does with your answers.
- Enter your typical daily solar surplus, your export rate and how you currently heat water.
- The tool compares the cost of the water heating a diverter would displace against your export rate.
- You get a clear verdict — divert, or keep exporting — with the payback when diverting wins.
Frequently asked questions
What is a solar diverter (like an Eddi)?
A device that detects surplus solar and sends it to your immersion heater instead of exporting it, giving you free hot water from electricity you’d otherwise sell cheaply.
Why might a diverter not be worth it anymore?
Because the Clean Export Guarantee now pays you for exported surplus. If your water heating is already cheap, the export payment can be worth more than the heating a diverter would displace.
Diverter or battery?
A diverter only offsets water heating; a battery can offset all your evening usage. If you use a lot of electricity after dark, a battery may capture more value — the battery sizer works that out.
Related tools
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Home Battery Sizer
Is a solar battery worth it in Ireland, and what size? The honest verdict.
These tools give honest indications using current published rates and guidance, not professional advice. Rules, prices and provider terms change — always confirm the current figures with the relevant official body, provider or qualified professional before you commit.