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Hot water diverter. Is it worth it with FIT?

  • 10-09-2022 3:03pm
    Registered Users Posts: 49

    I'm getting a PV system installed in November, am getting a 3.2kw system installed. I'm still unsure as to whether I should get an eddi (hot water diverter). To me it doesn't seem worthwhile financially but I've looked through posts on the Facebook page and everyone talks about it being a non brainer but I don't see how and want to be sure I'm not missing anything in my reasoning.

    The way im looking at it is using gas is a cheap way to heat water as it is. For two months over the summer I used 369kwh of gas to heat the water for an hour every morning, at 6c a kWh after discount which works out at about €22 for two months. When I get solar panels, id sell them 369kwh back to the grid and not have to pay €500 for the eddi. Surely I'd be better off doing that? I can't see how it's a no brainer like people are suggesting, what am I missing?

    Also, could I not just turn the gas water heating off and use the immersion if I wanted to heat water using my solar during the summer months?

    Can anyone point out flaws in my reasoning? I don't see how an eddi makes financial sense to a home with gas heating with the FIT rates being as high as they are.


  • Registered Users Posts: 1,694 ✭✭✭tnegun

    I've an eddi but got it before the FIT was announced I have only used the gas a handful of times since March and the tank has taken almost 1000kwh since it was installed last October. It is a long payback but with no guarantee of how much gas is going to cost going forward and up to 40% tax to be levied on what you make from FIT I think it still makes sense. If you have a system larger than 6kwh it makes sense too as you can't export anymore than that without a separate agreement. Out of interest you are you paying 6c per kwh to and what's their standing charge?

  • Registered Users Posts: 291 ✭✭spose

    I’m a big fan of the diverter but I have oil so not as cheap and I like not having to use the boiler at all for months on end. I reckon it’s paid for itself already but I put in an iboost and they were way cheaper than they are now. Don’t see it as a decision you have to make now though. They are so easy to install it literally in no more complicated than wiring a plug. See how it goes for 12 months and just buy one and put it in yourself if you decide you want it

  • Registered Users Posts: 2,211 ✭✭✭bullit_dodger

    Ultimately the correct answer here depends on your values and goals. It also depends a little on your rates that you're on.

    If the main thing is to save money, then the facebook posts are's a "no brainer", but in completely the opposite way :-) The EDDI will export your excess, but if you are getting €0.14 or so via a FIT, and only paying €0.08-€0.09 for a unit at night, then it makes total sense to heat the water up on night rate and export whatever you get during the day. A decent hot water cyclinder will lose 1C / hour (my double lagging jackets on my old copper tank is about 1.5c/hr) g

    If the rates are more favourable the other way, you'll really struggle too to make back the cost of the Eddi €500.

    All that said, I bought one before FIT and the changes in the rates, and I'd probably buy one again. The thing is, I treat hot water differently now. For 200+ days of the year, I've an abundance of hot water. Just finished mopping the floor in the kitchen after using 5-10 gallons. thing is back hot again. If I use it, or don't ..... I don't really care. Yeah, money wise it's not smart - but that's what i mentioned, it depends on your value system and for me I like the abundance of hot water over money coming in via a FIT (which anyone has yet to see - LOL)

  • Registered Users Posts: 1,035 ✭✭✭silver_sky

    Even without the FIT the diverter would have a long enough payback. My reasoning for going for one is reducing gas usage (water normally heated by gas boiler) and also quality of life element to it in that you would have more hot water available during summer as it's always heating if there generation and water to be heated.

  • Registered Users Posts: 1,919 ✭✭✭jkforde

    exactly, depends on 100% monetary considerations or more blended values... I love that fact that I've piping hot water all day and so is one less (first world) worry!

    🌦️ 6.7kwp, 45°, SSW, mid-Galway 🌦️

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  • Moderators, Sports Moderators Posts: 17,883 Mod ✭✭✭✭slave1

    This is a repeating topic.

    Financially no.

    Convenience yes.

  • Moderators, Science, Health & Environment Moderators Posts: 4,560 Mod ✭✭✭✭Tree

    And being able to automate it is great (alternative smart switches also work), so I have mine come on for night rate on days when the solar is going to be low. Less about saving money and more about being handy (and greener than burning gas just to heat water).