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Eddi V Feed in Tariff (fit)

  • 15-05-2023 11:09pm
    Registered Users Posts: 14,381 ✭✭✭✭

    I know this topic has came up before but think it deserves it's own thread.

    When I initially got Solar installed not that long ago (Feb 2022 while deal done back in Nov 2021) feed in tariff was uncertain and the Eddi was ideal.

    It's a great piece of kit that has never gave any bother since install and has a great app. Also using the information to feed back to HomeAssistant which I got setup with the help of other great posters here.

    I will be keeping it 100% as I have invested, this is for other posters to help them choose.

    Now present day:

    Firstly I am duel fuel electricty and gas.

    Recently got my hot water cylinder upgraded to a 300L tank with inbuilt immersion and stainless steel coil etc.

    Initial testing to heat the cold tank via Solar\immersion it took 5kw while heating with gas for 30 mins which used around 1kw achieved the same results.

    Cost wise based on fit is 92.5c electricity V at my current rate 9c for gas.

    Would be interested to know other posters experience.


  • Registered Users Posts: 2,412 ✭✭✭bullit_dodger

    The amount of Kwhr that takes to heat the tank will be very dependent on a number of variables, size of your tank. Starting temp of the water and what your thermostat is set to. I've recently just got a 200L tank and it took 5.3Kwhr today to heat it for the 1st time from cold. I do suspect though that the water going into the tank from the tank in the attic was colder than it normally would be, but

    Water Heating Calculator (

    does reckon that 150L from 20->60C takes ~7Kwh. So not too far off the mark. While it's a 200l tank, with the way the element wouldn't go right down to the bottom, I probably only get 140-150L or so up from 20C to 60C due to stratification.

    Moving from the triton T90 to this 200L with 3 bar pump, will be interesting. I'll heat more hot water now, but I won't have the Triton's 9Kw hitting the battery/grid. Since I'm on "deemed export" I'm just heating it from solar, but it's an interesting topic to think about when smart meters are in place.

  • Moderators, Education Moderators, Home & Garden Moderators Posts: 8,095 Mod ✭✭✭✭Jonathan

    Something isn't adding up there. A kWh of energy is the same whether it comes from gas or electricity.

    I wonder are you talking about getting the top of the tank heated to X°C, which is a usable temperate for a shower etc. If this is the case, it could be that the heating coil for the boiler is at the top of the cylinder and the immersion is at the bottom of the cylinder. In both scenarios, you'll still end up with usable hot water at X°C, but you'll have a lot more if heated via the immersion.

  • Registered Users Posts: 14,381 ✭✭✭✭Ha Long Bay

    Sorry I meant Kwhw. I cant seem to edit the post now. I was trying to explain when I put 1 Kwhw via immersions into a 300L cold tank it did very little but when I put 1Kwhr via gas it was able to heat water to a useable temperature.

  • Registered Users Posts: 1,063 ✭✭✭silver_sky

    Are you looking at 1 unit on your gas meter and considering that it's 1 kWh? the gas meter is m3. You need to multiply by the conversion factor. This varies but estimate with 11.5 should get in the ballpark.

  • Registered Users Posts: 14,381 ✭✭✭✭Ha Long Bay

    I could be wrong but did convert based on the formula. 1m3 X conversion factor - discount is around €.09 cent

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  • Moderators, Home & Garden Moderators Posts: 5,755 Mod ✭✭✭✭graememk

    I'd second what others are saying, heat is heat, a kwh is a kwh no matter the actual source of the energy. Heating a tank is very variable too, starting temp etc.

    If you used 1m3 of gas that would be 11kwh of heat used.

    But your point still stands, your 1 kwh of heat from gas is about 9c.

    If you were on a measured fit of 20c you'd be better exporting the electric and using the gas to heat your water.

    If your on a deemed fit, well the more you can use the better, but the eddi is only saving you what your gas rate is.

  • Registered Users Posts: 627 ✭✭✭JaCrispy

    Great discussion. Would love to see it expanded to compare an Eddi to an oil burner running at 90% efficiency.

    I have an Eddi and oil burner. I'm calculating that every 1kWr I put into my Eddi saves me around .20c on oil.

  • Registered Users Posts: 8,441 ✭✭✭micks_address

    technically when you cross 200 euro of FIT then you declare the balance as taxable income.. which probably brings the FIT/Eddi cost closer.. i use my eddi to top up the tank during the day after heating for an hour in the morning with gas at 6am.. usually means we never run out of water but the eddi gets very little use.. maybe 1kw per day.. i have the immersion turned down to 55 c as otherwise the water was scalding at the taps

  • Registered Users Posts: 1,402 ✭✭✭DC999

    And for a gas or oil boiler, you’ve a (water) pump that uses a certain amount of watts constantly when the boiler is running. Ok, that matters less in summer when there is a heap of solar.

    I’ve a 15 yr old gas boiler so it’s gotta be poor efficiency wise. It’s far from converting 90%. Plus I would rather not have the constant wear of it heating water – due to it’s age. As in when it’s gonna die and need to be replaced, I’d rather it died from usage heating the house. If an immersion dies it's not gonna cost me the 2.5k of a supply a fit of a new boiler.

  • Registered Users Posts: 1,786 ✭✭✭DownByTheGarden

    I have a 200l tank. The eddi heats either top or bottom. With the bottom element it is a bit higher up in the tank than the gas loop.

    We always have plenty of hot water from the electric elements and never run out.

    When using the gas to heat it it heats much more hot water, but most of it is just wasted as we never use the amount of hot water that the gas heats.

    So i think we will just stick to the solar heating the water.

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