If you have a new account but are having problems posting or verifying your account, please email us on [email protected] 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 [email protected]

Almost Free electricity from grid?? :) (update: not at all)

  • 08-02-2023 3:38pm
    Registered Users Posts: 165 ✭✭

    I just occurred to me that signing up for the EI Weekender tariff allows free electricity on either Sat or Sun for 15 Hours. (8am->11pm)

    So given my daily usage averages out at less than 15kWh (or 91kWh per week based on annual usage), would it be possible to charge a 90kWh DIY battery at the weekend and live off that for the remainder of the week, with the grid providing any residual short fall.

    In theory, 15hrs * 6kW would provide a nominal 90kWh for battery charging, excluding losses & standing charges. Also, the 1 weekend day would be free from the grid and only 6 of 7 days are required from battery.

    Now I know this is not very renewable and I am not planning to do it, but it does highlight a potential loophole in EI tariffs given that members here are already pushing 40kWh+ DIY batteries. For my 6 days every week I would only need ~80kWh or with a 40kWh DIY battery I could get everything half price. I am also pretty sure that EI would discontinue the tariff much quicker than any payback period on the investment in batteries & inverters.

    I couldn't see any fair use limits in the T&Cs. (Edit: there is so not likely to allow 'unreasonable' usage...see below)

    Again, I am not planning on doing this, just posting FYI.

    Post edited by oaklands on


  • Registered Users Posts: 1,377 ✭✭✭DC999

    Do it another way. Get a cheap rate each day (on a smart meter for 2-3 hours on an EV plan), or better still for ~9 hours on a D/N meter. I’d be veryyyy sure the providers have done the behavioural assessment on it. Like gyms, I reckon people use it loads at the start and then stop and go back to normal. Which was to never darken the door of the gym again in my case 😊 And the gym / energy provider ‘wins’.

    As a comparison, we used 40kWh some days in Dec (when it was Baltic cold). EV (1 and low usage), house (low usage), electric rads (to reduce the gas heating usage). Or averaged 210kWh a week in Dec. That’s highest usage we ever had. There are people here using 1500kWh a month in the depths of winter (multiple EVs, fully electric house – no gas or oil for heating or cooking). So no battery will cover that.

    And we've a small older EV (Leaf with 25kWh battery) - we need to charge it each night. Different with a new 80kWh VW that could be charged once a week. Dishwasher, washing machine all run once a day (4 in the house). Can't 'defer' dishes to a weekend. Meaning a cheaper night rate every night works much more easily for most I reckon

  • Registered Users Posts: 21,033 ✭✭✭✭ELM327

    Just get a day night meter and switch to energia EV tariff. 63 hours of 7c/kwh for me (13c for new signups) is better than a gimmicky free weekend day

  • Registered Users Posts: 165 ✭✭oaklands

    I am considering going the DIY battery route in 2023 along the lines you posted. I am still trying to get a Solar PV quote, but it seems my roof may be a non-runner (Solar Thermal HW + Roof Windows don't leave much space for panels) & garden is off-limits.

    However, cheap vs wins if you can get 80kWh charged for €0 on Saturday or Sunday. Downside is it would need ~8 sets of 16S 200Ah CALBs (guesstimate).

    It would only be an option for a few DIY battery pioneers & a non-runner if your daily usage was much more than 20kWh

    I would only try 1 or 2 sets for 10 or 20kWh DIY & in this case your suggestion would be preferable.

  • Registered Users Posts: 21,033 ✭✭✭✭ELM327

    If you have enough cash to pay for 8 sets of 16S calb cells (as well as an inverter, multiple BMS, lots of extra busbars etc) then I suggest you wouldnt have to worry about an electric bill anyway.

    Pretty silly to consider investing 25k or more (the price of the cells plus all ancillaries, conservative estimate too, and assuming 100% diy) in a tariff that could change or be withdrawn tomorrow and you're left with 25k worth of cells that you dont see any ROI on.

    Alternatively your ROI would be exponentially faster buying 1-2 sets of 16S calb cells, and switching to Energia EV tariff on a day night meter)

  • Registered Users Posts: 165 ✭✭oaklands

    I am not sure about 25K for a DIY CALBs system of 8x16s, based on my non-expert info. However, you are right in that the ROI would be too close to the lifespan of the batteries (~10 years??) which would make it a near zero sum game at best,if at all.

    OTOH, if you already had a big battery system or sourced one for cheap then.....maybe

    I guess the reason that Solar PV ROI works is that they are ~50% of the cost of DIY batteries per kWh with 2.5 times the lifespan with FIT as an additional bonus.

    I will really have to get the calculations rock-solid before considering DIY batteries. :)

  • Advertisement
  • Moderators, Home & Garden Moderators Posts: 5,520 Mod ✭✭✭✭graememk

    There is fair use but " we'll contact you if you use too much" on the website.

    Still would be better off just on a standard day night and only use night rate.

  • Registered Users Posts: 18,275 ✭✭✭✭kippy

    Sounds daft tbh even at ten k. So many possible issues. Spend a few weeks a year in the Bahamas instead.

  • Registered Users Posts: 14 Rogtronic1

    Hey @ELM327 How does one go about getting a day/night meter installed? I have a smart meter so Im pretty sure its impossible to go back. Happy to be proven wrong though :)

  • Registered Users Posts: 165 ✭✭oaklands

    Tnx, I see it now. So not a runner in any scenario.

  • Registered Users Posts: 21,033 ✭✭✭✭ELM327

    Contact your supply company. I went back, from smart to day night

  • Advertisement
  • Registered Users Posts: 21,033 ✭✭✭✭ELM327

    2.6k dollars per 16 raw cells here from PWOD and thats excluding the raw materials otherwise like multiple BMS, added busbars, probably multiple but at least one inverter charger, etc etc

  • Moderators, Sports Moderators Posts: 24,266 Mod ✭✭✭✭CramCycle

    Best I can see is

    Day 47.77cent

    Night 13.75 cent

    Are there better ones out there?

  • Registered Users Posts: 21,033 ✭✭✭✭ELM327

    No, thats the best day night rate available currently for new signups.

    I'm on fixed 28c day 7c night, but that fixed price contract is no longer available

  • Registered Users Posts: 1,377 ✭✭✭DC999

    13.75c night is good with rates as they are now. I changed my folks tariff in the last month. The best 24r tariff was around 40c. So you're getting the night rate for 1/3 of that. Get smart plugs and you can turn most dumb devices into timed ones and run them during night rate.

  • Registered Users Posts: 165 ✭✭oaklands

    @ELM327 to quote from your recent post below.....€1.4k for 16 CALB cells from PWOD.

    Even at this price it is still a non runner because of 'Fair Use' policy and likely ROI.......the dream was short lived :)


  • Registered Users Posts: 21,033 ✭✭✭✭ELM327

    Edit: Yes the prices fluctuate up and down quite a bit. They were lower during chinese new year, which is when I suspect that screenshotted post is from. In either case, 1500 or 2500 per 16, you'd need 8-10 batches so you're still going to be spending a lot.

  • Moderators, Sports Moderators Posts: 24,266 Mod ✭✭✭✭CramCycle

    My current one is Bord Gais at roughly 20c, provided my panel installation goes to plan, I will try and calculate the numbers. With the number of panels and FIT I am hoping that I'll have built in enough to take the sting out of the winter months and run the ground to floor heat pump overnight during the winter with that rate and then maybe a few hours during the middle of the day. Just noticed the standing charge is substantially cheaper than Bord Gais as well so we shall see. I have 12 days left to back out and switch over.

  • Registered Users Posts: 64,349 ✭✭✭✭unkel

    Non runner because of fair use, but it would cost less than some people make out. In recent months I have been paying about €1300 or a bit over for a set of 16 CALB 200Ah , so with a full DIY built, the BOM with costs is roughly:

    Cells 8 * 1300 = 10400 (for 80kWh)

    JK BMS 150

    Sunsynk hybrid inverter 5.5kW 1500 (you can add two strings of dirt cheap second hand PV panels to this for very little extra cost)

    extra busbars and other materials 250

    So a bit over €12k for an 80kWh system

  • Registered Users Posts: 64,349 ✭✭✭✭unkel

    @oaklands - "Now I know this is not very renewable"

    More renewable than you think. Why do you reckon the utility providers can offer this sort of deal, or why does cheap night rate exist? Not because they want to be nice to you. Because the wholesale off peak rates can be super cheap. Sometimes even negative. In the UK you can sometimes get paid for using electricity (when it is very windy and nobody can use the electricity for anything). That's when a pure battery system can be very renewable and zero emissions!

    @oaklands - "it seems my roof may be a non-runner (Solar Thermal HW + Roof Windows don't leave much space for panels)"

    I'm the exact same. South facing house roof (small semi D 3 bed house in a Dublin estate) and I already have 40 solar thermal tubes and 3 velux windows on it. So I started with a few panels DIY on my shed many years ago. Then I added 5 panels DIY on my kitchen extension the next year. Then I had a roofer fit another 5 panels on my roof in between all those velux windows and thermal tubes. Fast forward another few years and within the next few months I will have well over 40 panels fitted around the place. Where there is a will... 😁

  • Registered Users Posts: 165 ✭✭oaklands

    Yeh....I am currently trying to get a quote for 2-3KWp on my S, N & W roofs. (likely 2 x 400Wp panels on each roof, maybe a 3rd on S&N roofs.)

    The typical responses so far are:

    • won't work...can't make it work
    • not possible to install with with rosemary tiles (seems there are kits available for these tiles)
    • Can't design to comply with SEAI
    • The most common response is 'radio-silence'

    Other than the roof, the back garden is off-limits & the front garden would require planning permission and likely off-limits as well.

    So I will give it a few more months looking for an installer and move on to a DIY battery, charged at night. I am assuming they prefer to install a greater number of panels on 1 or maybe 2 roofs but not 3.

    On a related matter, my understanding of SEAI regs for panel placement on roof is:

    The PV modules must not overhang the edge of the roof at any point, must not extend within 500mm of the roof edge/perimeter, and must not be fixed at the ridge cap/tile (which in many cases may be cemented in place) or within 200mm of the top of the ridge.

    500mm is a minimum and some designs, particularly for taller buildings, may require a higher setback distance. Where less than 500mm is required, approval (planning permission) from a local authority may be required along with appropriate wind load calculations.

    So in plain terms panels must 500mm back from edge & not fixed at <200mm from ridge & not fixed on ridge/cap tile.

    I did notice on my recent EI bill that 63% is now from renewable sources, which is better than I had expected. So I presume they have lots from wind which would be available overnight and thus would motivate cheaper night rates. I have a vague recollection that years ago the night rate emerged because they needed to keep generators running at minimum levels overnight. However based on my recent review of Tariffs, it seems the 'market' is not operating competitively because the suppliers are providing cheaper night rates , but then penalising the daytime usage and topping off with a higher standing charge. It seems the main impact of smart meters is heading towards getting more revenue for suppliers and NOT for the benefit of end-users who end up paying for them. Regulator not doing their job it seems (to me).

  • Advertisement