If you have a new account but are having problems posting or verifying your account, please email us on for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact
Hi all,
Vanilla are planning an update to the site on April 24th (next Wednesday). It is a major PHP8 update which is expected to boost performance across the site. The site will be down from 7pm and it is expected to take about an hour to complete. We appreciate your patience during the update.
Thanks all.

Eddi vs oil

  • 17-04-2022 7:20am
    Registered Users Posts: 2,730 ✭✭✭

    Question from a noob. I have PV, I have an oil burning firebird. I can heat my 60L water tank with oil or I can use my new immersion to heat the same tank.

    I am adding an Eddi later this year, but for now it's a manual process. So when I turn it on its full blast 2.5Kw until hot.

    I was trying to decide whether it was cheaper to use oil or electricity. I don't yet have lots of spare electricity, only a 5kw battery and april is not as bright as March so far.

    Using this link I calculate, that my sunk cost for oil is higher than night rate, but cheaper than day rate. Am I right?

    I'massuming today's price for oil is 1.20 and my burner is 90% efficient. Night rate is .10 day rate is .20 roughly....


  • Registered Users Posts: 297 ✭✭spose

    There’s a lot of factors you can build in to justify why the payback is or isn’t there. I don’t think you can justify comparing just to night rate since if your showers are fed from that cylinder you’re unlikely to get your full days usage out of a 60L tank heated during the night. We know costs are only going to go up so the payback will likely be there. For me I like that I don’t have to use oil at all from about April to October. No watching oil levels to reorder, no wear on the boiler, doing a bit for the environment taking a few litres of oil burning out everyday and there’s always hot water there. There’s cheaper options than the eddi too if you don’t need or want the extra info/control from it. I fitted an iboost in about 15 mins, no more complicated than wiring a plug.

  • Registered Users Posts: 528 ✭✭✭mike_2009

    I have night rate and a 6kW battery - during the summer I turn off the gas heating and just run off the Eddi. I do a scheduled boost in the morning for an hour to get the tank up to temp and if there's decent sun during the day it gets another boost then for free. In the late afternoon/early evening I do another scheduled boost with the Eddi but this isn't needed if there was decent sunshine during the day. My gas bills drop very low (just cooking) and the house is very comfortable all Summer. I took out an electric shower so that both showers use the main hot water tank as I was doubling up hot water generation and there are just two adults in the house. I have an EV so the night rate really makes sense but even without that, if you can timeshift offpeak electricity by boosting the battery at night and use this during the day, while it does use more cycles on the battery it helps reduce your electricity costs a bit. Slightly higher standing charge though.

    So, Oil fluctuates in price, Electricity is only going up. At least you have two good options. Maybe 3 months of the year, one makes more sense and revert the rest of the time?

    There's a youtube channel called EV Puzzle and he's been playing with oil fired heaters in each room on a smart plug that measures power and working out if it's cheaper to use that vs his Oil/Gas (?can't remember which he had?) central heating system and goes into a lot of detail. Also worth a look. An Air to Air heater can also do cooling, has great COP and is relatively cheap as an alternative also. But each approach requires an investment.

    I'd suggest try running off the Eddi and leave Oil along for a fortnight if you can measure usage and see if your circumstances point a clear path one way to the other?

  • Registered Users Posts: 2,730 ✭✭✭yankinlk

    Thanks to you both, I guess my logic and math is sound?

    I'm thinking I will set to boost on night rate and disable oil until later in the day. Seems to take an hour to heat the tank roughly in the morning.

    Is there a problem if oil and immersion/eddi overlap? Say both are on at same time for example heating the tank? I assume this is OK, and thermostat will turn off each when heated up?

  • Registered Users Posts: 528 ✭✭✭mike_2009

    The Eddi won't mind, it just keeps going until the target temp is reached and then bows out. I'd assume your boiler will just pour heat into the Rads as none is lost to the hot water tank if it's up to temp? Might be a quick question to your plumber?

  • Registered Users Posts: 2,730 ✭✭✭yankinlk

    I have two zones, so rads are off now. Just zone 1 for hot water tank. Thanks I think it will just heat twice as fast. When the excess sun months finally arrive I will drop oil completely.

  • Advertisement
  • Moderators, Home & Garden Moderators Posts: 5,758 Mod ✭✭✭✭graememk

    Although this is gas, but the same principles apply for condensing oil boilers.

    Most boilers rarely hit 90% especially heating DHW so id be saying 80%

    60L tank isn't that big though, average shower uses 56 litres, but that total water, say half of it is hot? You might squeeze 2 showers out of it.

    Its gonna take a while for oil to come down anyway.

    At 80% efficiency a litre of oil ,has about 8kwh of heat energy. At 10c night rate is cheaper than oil at €1, Per kWh,

  • Registered Users Posts: 10,803 ✭✭✭✭the_amazing_raisin

    I for one am very disappointed that this thread isn't about someone named Eddie taking on the oil industry 😁

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 528 ✭✭✭mike_2009

    Get a bigger tank and have Eddie drive it....?!! More water and we'll bring the popcorn to watch the fight with big oil!

  • Registered Users Posts: 2,414 ✭✭✭bullit_dodger