I spent ages thinking on the "best" way to model things, and in truth, there is no perfect answer. Really does depend on so many variables - that people have to crunch your own numbers to know for sure. Your own unit rates, the provider your with (some have penalites if you use too little!), your usage plays a part of course and also when in the day you use things (ovens, gaming pc's, etc), are you on day/night tarrifs. etc, etc.
Generally, if your someone reading this and you can't be arsed to crunch the numbers (I know not everyone is so inclined....hehe) your safe enough with either a 2.5Kwhr or 5Kwhr. Larger batteries (than 5Kwhr) have their place for sure, but you have to have the consumption to utilize it or your effectively wasting money. Head over to the DIY battery thread for good advice there if your looking to get something big on the cheap!
One thing you can update your spreadsheet with Garo is that you have 90% efficiency in and 90% out. Giving you an overall roundtrip of 81%? I used an overall roundtrip of 85% - but that's actually a little pessimist apparently.
(959) Givenergy AC3K 5.2Kw home/solar battery discharge/efficiency test - YouTube (skip to last minute for the details)
He found 87% and some of the other comments there on that Youtube page reporting that 89% - 90% is pretty standard for an AC battery. If we use 90% you drop the payback time further from your 10.42 years, although naturally it drops the payback time across all sizes of course irrespective of size.
I also realize the efficiency will slightly deteriorate over the lifetime of the battery. So maybe 85% roundtrip is fair....dunno.
We're probably boring people :-)
I think this test could easily be off by a few percent. He didn't explain why the app thought it was discharging at 2.2kW when the only thing that was running was a 2kW inverter. The Givenergy battery app may not have measured charging or discharging losses accurately. One of of the denizens of this forum did a test with professional grade equipment and found 80% efficiency for a LifePO battery. Efficiency also depends on charge and discharge rates, battery temp etc. We can go with 85% as a compromise. That shortens payback time by half a year.
Thats my battery efficiency since Jan, Measured externally on an emon tx, AC kwh out of battery / AC kwh into battery, July and Aug have been warmer... maybe that improves it.
You referring to Unkel's test a few months back? Quiet impressed by that too , nice piece of work that if your reading Unkel. Although these Givenergy batteries are apparently AC batteries.
Now, my knowledge here is a little spare (so feel free to correct!!) - but my understanding was that full load discharging on these type of batteries would be 90% efficient, and that loads in the low 100's watt range they would be closer to 98% efficient. I'm not really sure how or why they can achieve those figures. Assuming 90% was the normal for full discharge, and since that steady load your man had of 2kw on the battery wouldn't be indicative of my normal house which is 1kw, I'm hoping for a higher figure than 85% myself. For sure, I'll be giving some real life measurements once I'm up and running.....
Just as an FYI : German start-up offers 5.2 kWh AC battery that works without inverter – pv magazine International (pv-magazine.com)
(I probably should stop hogging the thread and we should get back to quotes, but maybe others out there find it interesting. :-)
Let's switch to the correct thread. We have gone way off-topic. https://www.boards.ie/discussion/comment/117977281#Comment_117977281
Thanks be, this rabbit hole was getting confusing.
€3950 for a 5.2 kWh LiFePO4 battery AC coupled into an existing system with a non-hybrid inverter. Less €600 grant.
Bit high given that you can buy the parts for under 3k. https://midsummerwholesale.co.uk/buy/giv-energy/giv-ac-3-5200-bundle
Interesting that your link shows that it can support dedicated critical circuits as is - I was quoted an additional €1100 plus to provide power to one or two dedicated circuits during power cuts. Maybe the guy that I was talking to had another solution in mind
Most inverter have an EPS output now. Maybe the extra cost had to do with wiring up those circuits into the house? There's also the isolator/flip switch to consider. I would ask what precisely you are getting for that 1100. Mayb they just don't want the hassle and are quoting a go-away price?
Might be a go-away price - he didn't sound enthusiastic. I'll find out exactly what's included - thanks
Final quote, followed advise here and went bigger. Seems very fair but would love some thoughts. Have both a heat pump and 2x EV
Could anyone point me in the direction of a podcast about domestic solar.
Just to hear chats/discussions and absorb info.
Thanks
I know someone that paid 20k for for 7kw system with battery but im not sure on the details.
Talked into it by a door to door sales man in Naas.
Some sort of voucher scheme 🤣
My first quote:
4.2kw system
11 x 400w solar panels
6kw Hybrid Inverter
4.8kw Battery
Hot water diverter
€13.5k before grant
Hi Guys
Am a newbie to this forum and am looking for advice on installing solar PV. I got the below quote recently which is similar to the one reference on this thread and I was wondering if anyone could advice if this is a reasonable price.
10 Panels 380W Q-cells
3.6kW GivEnergy Inverter
5.2kWh GivEnergy Battery
EDDI smart immersion
Quote Total € 9,880
€ 6,950 after grant
I would appreciate if anyone could recommend other company or send me a link to the Saas company that is being talked about on this thread.
Thanks for the help.
Not to bad but the inverter is to small
Not sure you'll need that size of battery as well as a diverter with a 3.8 kwp system
Too expensive. It can be bettered.
That's awful.
Can you message me your installer details? Interested to find out is there a pattern in these bad quotes
Poor bastard. An Active company?
Not sure myself either but could it be because I listed I have an EV hence the bigger size battery?
It's so bad it sounds unbelievable tbh.
What size was the battery?..
That doesn't make sense. Having an EV should have nothing to do with size of the the solar batteries. I'm pretty sure you won't be charging your EV from the batteries.
Similar dwelling and heating system, what do you advise for me?
What sort of cost? I've been quoted 20k
Cheers
Well thats a record and not in a good way.
Did the company have the number 8 in their name.
No the chaps with 8 in their name haven't rang me back yet!!!
This was for 6kw panels, hybrid inverter and battery storage!
It should be under 10k.
I've 8 x JA Solar 305W Mono panels installed back in Oct 2018 and generally I'm happy with the setup but now want to expand and I'm interested in getting a battery storage. I don't have a hybrid invertor and I'm wondering if it possible to install an battery storage unit that doesn't need a hybrid invertor. I've been on to the company in Eninskillen and awaiting a quotation from them but could anyone PM me other companies that they would recommend for a quotation.
Many thanks and this site has been great for info regarding PV
Short answer.. No. I asked it in the last few days. The reason is a few pages back
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