Solar PV and Eddi

tech

Hi

very close on ordering 18 panels all south facing and possibly 10KW battery, I dont think the Eddi is worth the €600 approx as I ca use the imerrsion on Cheap rate power or also put it on during day when the sun is out ?? I plan to charge batteries during day and top up @ night on Cheap rate,

Do you think the Eddi is worth it?? better off putting the €600 towards a 2nd battery?

Tree

You should find a dozen threads on this exact topic. IF you don't fancy finding them, the short version is, not worth it in terms of return on investment but a lot of folks like the convenience factor.

In financial terms, i did the sums before getting my system and neither batteries nor an EDDI made sense- the payback period is just too long, with a strong probability of having to replace the battery especially at or before the point it had paid for itself.

So i opted for the grid battery instead.

If your priority is to use as much of the electricity on-site as possible then sure, go ahead. But don't con yourself into thinking the batteries and eddi are saving you money.

tech

Grid battery system = FIT?

bullit_dodger

Yeah, I have an Eddi which I bought before FIT was implemented and back in the day it made a lot of sense as we were getting paid €0 for all electricity we exported to the grid. With FIT it'll never make you money back.

Disagree about the batteries statement generally though. For sure, there are people with specific consumption profiles where a battery does not make financial sense, but I think for most people (70% ?) batteries will pay for themselves in 7-8 years assuming you don't get ripped off in the initial installation. Go DIY route if you can and you'll probably see a battery pay back in 4-5 years or so. The main thing they do is reduce the bills in winter by allowing you to charge at night rate and stop you from having to import at full day rate. I'm about €30-40/month savings from a battery alone. (8.5kwhr)

Basically you have to crunch the numbers for your house.

curioustony

I'm with @bullit_dodger on this. You need to run the numbers for yourself.

For the numbers the CRU specify for the EAB, with no battery, a 10.9kWh and a 20.8kWh you get this for an estimated annual bill:

A battery can also be very handy in a power outage... Depends on what you want, much like the eddi.

No solar in any of the above calcs, just inverter and battery on a decent smart plan, there are a few more if you know your numbers

pad406

I got 17 panels (7.2wWp, south facing) 10.4kWh battery and an Eddi mid last October. Been working out what kind of savings I've been making and so far it's like this:

Year	Mth	CostToCharge	ElecCost	Savings	NoDays	PerDay
2023	11	38.43	113.59	75.16	30	2.51
2023	12	38.38	117.59	79.21	31	2.56
2024	01	41.38	119.47	78.09	31	2.52
2024	02	35.50	106.89	71.39	29	2.46
2024	03	32.05	80.90	48.85	31	1.58
2024	04	44.74	70.47	25.73	30	0.86
2024	05	26.94	39.83	12.90	20	0.64
Total		257.41	648.74	391.33	202	1.94

As you can see Mar/Apr/May has less savings, mostly because

a) I'm not using the stored electricity from the battery during the high daily rate

b) I'm taking the cost to charge of any Solar top-up as being 21c (my Fit rate) rather than the cheaper 10c at 2am-4am.

Currently I'm not discharging my 50/60% ish remaining battery early AM as the Eddi just sucks it all in, when I do that will increase my savings.

Which brings me to my other issue with the Eddi. I don't really need hot water all day long and it stops me discharging at night. I've got a spare smart timer switch to add into it but first I'm going to set the excess on it very high and set the timer on it to top up the heat early evening, if that doesn't do what I want, then I'll put in the timer switch.

I initially got the Eddi for more long term, when the FIT reduces as it inevitably will. IF it had the ability to better control it, timer settings to put it into stop mode being the prime example, I'd be a lot happier with it.

Edit, Mod : Mobile boards shreds tables, so here what desktop users see:

slave1

EDDI is a very flexible device, what exactly are you trying to do, can’t make your post out exactly?

graememk

I think discharge battery to grid, but not have the eddi pick it up.

It can be done in home assistant

pad406

https://www.boards.ie/discussion/comment/122162901#Comment_122162901

So my current setup is as follows:

Eddi excess set to 250w

Eddi comes on from 2am to 4am to heat cylinder

Again at about 6:00 for 30m for a quick boost for morning showers (actually I think this is not needed)

Hot water will be used during the day also.

But the EDDI keeps kicking in all day, using anywhere between 3&5kW which I don't need. I just need hot water again about 6/7pm. And not even much at that point.

The if I try and discharge the battery at 12-2, EDDI swallows most of it and I get very little FIT.

Today I have set the excess to 5kW so I'll monitor that.

https://www.boards.ie/discussion/comment/122162965#Comment_122162965

I've heard of it, but don't know much about it. From the little I've googled seems I need a Rasberry PI module first? Must dig into it a bit more. Is there a Home Assistant for Dummies type thing?

bullit_dodger

https://www.boards.ie/discussion/comment/122163054#Comment_122163054

Just set your export limit to (say) 4Kw or greater than the max level discharge of your battery. Wouldn't that sort it? You could dump your battery out to the grid at 3kw, but since that's not higher than the Eddi's threshold, it'll do nothing.

For your "I just need hot water again about 6/7pm, but not much at that point", you have a schedule in the Eddi to turn on the "Sink" for 30 mins, assuming you have a dual element like most tanks.

What am I missing?

pad406

https://www.boards.ie/discussion/comment/122163336#Comment_122163336

True, but basically then the Eddi is a very expensive timer for the immersion?

All it really needs is a schedule where you can turn it off for periods, small thing would make it so much more useful

bullit_dodger

https://www.boards.ie/discussion/comment/122163472#Comment_122163472

True, but basically then the Eddi is a very expensive timer for the immersion?

Yeah, it's an expensive timer for sure! But it's a "sunk cost", you have it now might as well use it, but your right…..a quick way to set a "block out time" for it working woudl be relatively easy for them to support in the firmware.

https://www.boards.ie/discussion/comment/122156226#Comment_122156226

Remember that unless you have the money sitting in the bank doing nothing, the cost will be significantly higher than the headline cost as interest will need to be included. Battery efficiency will drop over time, and electricity prices are highly likely to fall further during the year (though not close to 2019 levels) which will further reduce available savings.

Maybe the options I was given for including batteries in my system were just terrible. (The David Hunt quote analyser says otherwise). But my own calculations (including cost of credit, assuming 100% charging efficiency even though actual is more like 80%, and using current electricity rates) suggested at least a 9 year payback period. If the battery lasts for 13 years (3 years past the guarantee period) my unguaranteed annualised return on investment was under 3% which is frankly terrible.

The FIT will almost certainly drop roughly in line with the drop in electricity prices, but unless it drops to 2c a KWH again it's not going to make financial sense to get a house battery. The inverter and batteries are 10-15 year assets— solar panels are 30 year plus assets— the maths is different for each part of the system.

I haven't checked the numbers, but I'd question whether batteries make sense from an environmental perspective on an individual level (although if a battery were installed in every home in the country it'd obviously go a massive distance to backing up renewable energy and facilitating energy independence on a national level).

That said, there's nothing wrong with dropping €5k something just because it's shiny and you want it— if you can afford it.

bullit_dodger

https://www.boards.ie/discussion/comment/122164875#Comment_122164875

Ahh the good old battery argument comes up all the time. There's no right/wrong answer. You have to crunch the numbers which are applicable for your house. Couple of things which you might not be aware of though.

• I've recently gone through 1000 cycles in my battery (1005 to be exact) and so far not seen even ~1% drop off in storage capacity. Why? Well I've a GivEnergy battery and while they sell you a 8.4Kwhr battery, under the hood they actually give you a 9.5Kwhr battery or something, so while it might be slowly depreciating, it's a 12 year unlimited guarantee. I expect to have full capacity after 12 years.
• My battery aside (where they guarantee storage after 12 years) on a different make/model even after this time it's not like your battery suddenly stops working. It'll still be capable of storing 80-90% capacity as it slowly depreciates further.
• Regarding round trip efficiency, they claim 93%. https://givenergy.co.uk/products/battery-storage/
  scroll down a bit on that page. I don't get 93% in my own tests, but I do get about 89-91%

Most people who consume 15-20Kwh/day or more though would get value from a battery. Strangely the whole FIT moving up/down doesn't "really" change the value proposition, but rather changes the strategy that you'd employ.

Depending on your usage case you might "charge & dump", if your FIT is much higher than night rate. Or alternatively if FIT is lower and your suggesting €0.02…..don't forget that for many of us we bough batteries when there was €0.00 (no FIT) and they made sense when FIT was €0.00. FIT is effectively a bonus to the equations. The trick is the battery stops you from importing high rate leccy. Some of that you can "load shift", but it's not an easy thing to compute all up.

Never been a cheaper time to buy batteries. That said, again it's not a case I'm right=your wrong. No, there's a lot as mentioned which needs to be factored in. Depends a lot on how much you use, when you use it etc. but I guess 60-70% of people would do right eventually (7-8 years) with one, but that's not to say it's right for everyone.

https://www.boards.ie/discussion/comment/122167478#Comment_122167478

My daily usage was around 13 kwh with about 65% at the day rate on average. In the 20 days since I got solar in, that's at 5kw per day with a 50-50 day-night split. (I also turned off every radiator in the house so- in the absence of zoned heating controls- I could use central heating for hot water instead of the immersion. That obviously made a significant difference).

So to be fair, my numbers were never going to work for a battery, as it'd save maybe 50 cent a day at current usage levels (but probably more on average over the year).

At my current rates (Energia) there's a €0.15c difference between day & night rates, and €0.05 between FIT and day rates. Assuming 10kwh battery and 90% efficiency it'd be about €1.55 to charge and the discharge would displace €2.90 of daytime usage. So €1.35 saving per day of €493 per year. That's over 10 year payback period excluding the cost of capital.

Say the 10kwh battery enables the user of 20 kwh at daytime rates to completely eliminate their day-rate usage through an even split of night time charging and solar. The difference for solar is going to be another €0.50 (difference between FIT and day rate) per day or €183 a year, bringing the grand total saving to €675 or a payback period of about 7.5 years excluding the cost of capital for a €5k system.

I'd suggest though that someone using 20kwh at day-rates needs to focus more on their usage patterns rather battery options. It seems very high to be using 20kwh in total per day, never mind at day rates.

A 7.5 year payback period is definitely much better than 10 years. But including the cost of credit, for me that 7.5 years is actually 10 years for 2 cycles per day. My credit union's loan calculator doesn't stretch long enough to know how long my payback period would be at 1 cycle per day, but I'm guessing it'd be somewhere around 13 years. This is based on €5k cost for batteries & the premium for a battery ready inverter.

I just don't see the maths supporting an investment in a battery at current prices for batteries and electricity.

Don't get me wrong though, I think batteries should be mandatory in all new homes and heavily subsidised in existing homes. As I already said, it'd help an awful lot on the national journey to renewable energy & energy security/independence. I just don't see the logic on an individual level.

Unless you just want the shiny kit. Shiny kit syndrome is nothing to be ashamed of, and something I suffer from regularly myself!

randombar

For me batteries are a no brainer. (20kwh + Heatpump)

Made a massive difference when I put in a small one a good few years ago now.

I've upgraded to SolarEdge since 20kwh worth and they are fantastic.

Just on dumping back to the grid alone (between 12 and 2am) this year I've made €400, that's not counting all the solar dumped etc.

Batteries mean 90% of solar I generate I get paid for.

90% of my electricity from the grid comes from 2 to 6am, aiming for 95%

Full backup in power cuts

Forgot to charge the car the other night and just charged in the morning knowing it was coming from batteries + cheap rate.

I've tried to move a lot of my consumption to the cheap window but realistically washing machines, dryers etc. I just prefer to have them running during the day.

My ROI is probably close to 8 years I'm guessing but that's not taking into account the flexibility I have + the batteries have a 10 year warranty so once the 8 years are up I'll be well in the green.

allinthehead

Having automatic backup of my essential circuits is nearly worth the cost of the batteries. I don't even know when the power goes anymore, and saving the Sunday roast a couple of times is almost priceless.😁

bullit_dodger

https://www.boards.ie/discussion/comment/122169122#Comment_122169122

Yeah, can't argue with the math you've given there. I'm with Energia myself, although out of contract with them and on D/N it's €0.38/€0.185 so it's a good difference.

One thing to be aware of though is that with the state of the suppliers out there, there's a plethora of different tarrifs to be had. One of the regulars here is paying a ridiculous €0.06 (or something) night rate and then can export back to the grid at €0.20 or something? That's something that you (or I) could get too, so where you might be thinking that batteries don't make sense on your tarrif (and you'd be right)……there could well be tarrifs out there where you could make a LOT of payback.

Quick math on that. Buy 10Kwh at €0.06=€0.60, sell back to the grid at €0.20= €2. Take a 15% loss on the €1.40 difference and that's €434/year. Factor in storing solar where you avoid all peak charges at €0.35+ and your down in the 6-7 year range.

Main thing I think which benifits the overall bottom line is in winter solar is pants. My 6.5Kwp system generates on average 2kwh/day….kinda rubbish really when you need power the most on those long dark nights. So charging up at night stops me from having to use those €0.35+ day rates……well a lot of them anyway! I still end up importing some, but my bills are better to the tune of €60-70 every 2 months.

Again, can't stress this enough….battery ain't for everyone. Depends on the circumstances. Factoring in interest on loans etc is a valid point.

eltoastero

I still advocate people to get an Eddi, but my arguments rarely promote it as a "cost saving" measure.

Exporting via FIT would gain me 24c/kWh, heating the water at night costs me 18c/kWh (rate for the entire night, many will have a cheaper 2 or 3 hour window in the night).

So I'm "losing" 6c/kWh if I heat my water during the day.

But, the EDDI brings so much flexibility. I can control my hot water remotely (the EDDI replaced a very basic mechanical timer on the immersion). I now heat my water at 6am, using about 1.3kWh and that's enough for a couple of early showers. Then during the day I let the tank heat as much as it wants/can from solar (usually about 3kWh - 3.5kWh), so that covers more showers, baths for kids, dishes etc.

I also really appreciate not using gas to heat my water during the day, instead relying on hyper locally produced electricity. That "cost" to me of 12c - 18c per day is worth it for this environmental benefit alone.

Also, adding the Eddi gave me better control of my Zappi v1 (the old hub with the zappi v1 wasn't the most reliable for me) - so that too was a benefit.

slave1

When the EDDI was around €400 it was doable, the high cost rise has made it a difficult purchase now but the way I look at it is you are already in for multiple grand, with electrician already there etc it's worth it for convenience

bullit_dodger

https://www.boards.ie/discussion/comment/122189013#Comment_122189013

I'm sort of on the same page as you, that I like my Eddi. Is this perhaps buyers self-justifiction that they bought a good device? Who knows?

Problem though is that all those things you suggest while they are useful things, such as setting schedules, access remotely can be done with better options. The link below for £23 you can do the same. Turn on/off via your phone when your down in the pub, set timers/schedules, automatable (if you want) via home assistant - and it's not hard to wire in over an existing "Sink/Bath" switch.

Lot cheaper than €500+ (or is it 600 now) for an Eddi.

Don't get me wrong, I still use my Eddi to heat water at day time, but that's more around the fact that if I did it at night time I'd be way over that €400/year export limit - and while I'm sure if I didn't declare it , it would not be found, but I just don't want to give the feckers any more tax than i need to :-) …. so happy to heat my water for 7-8 months a year from solar. Again though that's not to say that an Eddi is right for 95% of people - but I like mine.

https://www.amazon.co.uk/Immersion-Heater-Control-Assistant-White-1pcs/dp/B0CKTFNCB3/ref%3Dsr_1_5?crid=APHSYNZXATUZ&dib=eyJ2IjoiMSJ9.D_PGTPAnIz6XODrpQwmCiOR0uVFEa33TTeHAGsn6DkOoPOtdjdfxlPLYTa__CxnRH_Ucy7HUKvyVIaI2qIRpfgrKQXl1s-kFONl_eeZBY0qv1AxQqxUiEiQBCcrAOX25XySBCq5mad_npdEnndTBiSCWp4YA68LLQF09HXGYFw1Kvy0SuxVT40xwEeaDjyDh7kJW4l_3f-mfDuAxJkW3CVRtX0P3ZYky5BIVN6Pn4nuxCy7-BAZ1hQNmbUroHlrcz4WFsTvMKFNo0ylY0jDTN_KchyyHR7COyrzm8amDMvU.6aWrE0vJGtpblpHF7gQ3w_AKkYCNIFyogLWtLRsvFFw&dib_tag=se&keywords=wifi+immersion+heater+switch&qid=1716984641&sprefix=immersion+wifi%2Caps%2C294&sr=8-5

slave1

..but is that not an on/off option, with the EDDI it can manage any excess eg. 1kW whereas the on/off is 2.8kW or nothing

bullit_dodger

https://www.boards.ie/discussion/comment/122199327#Comment_122199327

True - but the person in question was doing most of the heating at night time.

Exporting via FIT would gain me 24c/kWh, heating the water at night costs me 18c/kWh (rate for the entire night, many will have a cheaper 2 or 3 hour window in the night).

So I'm "losing" 6c/kWh if I heat my water during the day.

Again, I'm a fan of the Eddi for specifically the reason you list slave but we had ours before the playing field changed. There's probably people out there who aren't aware that their are way to solve the scheduling, remote access problems for far cheaper.

I'd buy an Eddi again, but not to save money :-)

conor_mc

I removed an Eddi from a solar quote recently, only saved €350. Might be starting to regret that decision now!