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Is it worth my while getting a battery?

Bluefoam

I've got 2 solar hot water panels on my roof, that work independantly and give me water for showers for almost 6 months of the year...

I also have two PV panels (spec unknown), that were installed as part of the build, with a 5KW inverter. I've generated about €500 of power over the last 18 months & in the past few days my daily generation has been between .4kw and 2kw. april was 48.8kWh. It doesn't make sense for me to go on a smart meter plan, the increased charges would be more expensive than a regular contract even when recouping from the grid. I'm confident that the power I've propduced on my roof is going straight out of the building without any of that power being used by me...

Is it worth my while adding any sort of battery? It seems like it'll cost me more than its worth... I believe Zappy are working on a smart car charger that has a bttery built in (draws from solar as a priority), I don't have an welectric car, but I'm sure I will eventually.

Theres no more room on my roof for more panels...

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the_amazing_raisin

For my own experience, I just got a 10kWh battery installed to complement my 6kWp of panels

Last month I generated 665kWh of which I consumed 417 (65%). This was while using the Zappi to charge my EV for free for nearly a month, giving me over 500km of free driving

I also imported 447kWh from the grid

In the past two days, I've imported 2kWh from the grid and my self use rate is over 90%. Multiply that out for a month and add in some extra for charging the EV you're probably looking at ~140kWh of consumption, almost all at the cheaper night rate

What I've found is that having the battery takes the thinking out of the solar panels, you just start the appliances sometime in the afternoon when the battery has charged up

Having the Zappi is a bonus, but I don't think I'll be getting the same levels of free driving as last month

Now in your case, you'll need to consider how much power you can get out of the panels on a good day and how big a battery this can fill, which will kind of determine the size of battery you should get

You may also need a new inverter if your current one isn't a hybrid inverter, which could add some consideration costs

DC999

For you, a battery is not worth it. You produced 50kWh in April, my 16 panels did 400kWh. And mine isn’t a large system.

If you’ve a smart meter you can paid for the units you don’t use (called FIT) and is ~20c a unit. So you’d get 50units x 20C for April as a refund on your bill. You’ll never recover the cost of a battery. Your roof is full you said so you can’t add more solar.

I’d suggest people look to get solar first, then a battery is a ‘nice to have’.

Big Lar

For me the battery is a win as I charge it by night in the winter months on cheap electricity and use it by day, I reckon thou its only a matter of time until the night rate is reduced from the current 9hr window as with all the electric cars coming on stream there will be no requirement for the grid operators to sell surplus energy cheaply by night.

jim-osullivan

How long does it take to charge a 5kw battery from the grid.

the_amazing_raisin

https://www.boards.ie/discussion/comment/120554861#Comment_120554861

Depends on a few factors including your inverter size and how much power it can charge the battery with, and how much power the battery can be charged and discharged with

In general, a 5kWh battery would take 1 hour to charge from a 5kW inverter. A 2.5kW inverter (or if the battery is limited to this for whatever reason) would double the charging time

jim-osullivan

Thanks for reply.

I was asking about charging from the grid as I am considering using the 2am to 4am Electric Ireland night boost.

Also would like to know how long would it take to charge 10kw battery from the grid.

Can these be charged within the 2 hour period.

the_amazing_raisin

https://www.boards.ie/discussion/comment/120555229#Comment_120555229

Do you know what model inverter you have? That'll probably be the determining factor

Btw, battery capacity is kWh not kW. Kilowatts are instantaneous power whereas kilowatt hours are energy capacity.

A 10kWh battery would need a 5kW hybrid inverter minimum to charge in two hours

A good analogy is kW is like horsepower for an engine, and kWh is the fuel capacity of the tank

jim-osullivan

Thanks again

The inverter is Sofar Solar 4.6 kw total invertor rating

graememk

https://www.boards.ie/discussion/comment/120555435#Comment_120555435

I think your max charge rate is 3kw

So 10kwh will take over 3 hrs,

Mr Q

https://www.boards.ie/discussion/comment/120555435#Comment_120555435

Do you know if it is a EP or ES version of Sofar hybrid. The EP version would charge at 5kW

jim-osullivan

It's the ES version.

Ginger83

https://www.boards.ie/discussion/comment/120549497#Comment_120549497

Do you mind sharing the battery type and cost?

the_amazing_raisin

https://www.boards.ie/discussion/comment/120556754#Comment_120556754

I got 2 of these batteries, but tbh they're pretty much all the same these days

https://www.failtesolar.com/cfe/5-1kwh-lithium-battery

I'll PM details of who I bought it from and the price

Bluefoam

https://www.boards.ie/discussion/comment/120557275#Comment_120557275

I would be very interested too. I'd be grateful if you'd share the info with me.

the_amazing_raisin

PMs sent

alan kelly

I have a 5kw battery and also charge at night rate,, should I continue this during the summer ?

I charge both cars at night and heat the water for the showers. I have a heat pump but prob won't use it much during the summer months ?

the_amazing_raisin

https://www.boards.ie/discussion/comment/120561418#Comment_120561418

You probably don't want to fully charge the battery at night, but you'll likely want to keep a charging window to ensure the cars don't drain the house battery

I've mine set to charge from midnight to 3am to give the cats 3 hours of charging, that's more than enough for now to keep up with any diving we're doing

I've set the inverter to charge the house battery to 40%. I could go lower but it means I've got some usable energy in the morning and it won't start importing from the grid before the sun starts shining

alan kelly

I charge the 5kw battery at the low rate between 2-4am and allow it to start using the battery after 8am,, ie the first 5kw used after 8am in the house is from the low rate through the battery..

bullit_dodger

https://www.boards.ie/discussion/comment/120561457#Comment_120561457

Bear in mind that day rate starts at 9am in the summer. So you are in effect using your battery with the 10% losses etc to provide "night rate" when in fact you could simply take it from the grid anyway.

Need to start at 9am Alan. In winter it's 8am alright.

graememk

https://www.boards.ie/discussion/comment/120562138#Comment_120562138

From what I've seen, smart meters do observe DST and don't move like the traditional d/n meters

bullit_dodger

https://www.boards.ie/discussion/comment/120562243#Comment_120562243

Ahh good to know - didn't realize that, but I suspect Alan is on the old D/N meter like most of us as the smart meters "in D/N mode" will only be available from "Autumn 23".

alan kelly

Cheers folks, Im actually on a smart meter but on my contract is the Home Electric and Night Boost from Electric Ireland.

Day: 08.00 - 23.00, Night: 23.00 - 08.00 and Night Boost: 02.00 - 04.00.

Surely this stays the same in summer ?

graememk

https://www.boards.ie/discussion/comment/120563019#Comment_120563019

Yeah it stays the same on the smart meters as far as I know

oojohoo1

Hey,

It depends on your plan.

We are with SSE and on a 24hr meter rate as that's what works best for us.

Import rate is 32c after tax. Export rate is 24c. So if you think about it, if you export everything and buy it back at those prices, its only costing you 8c per kWh.

We used 885kWh from our battery in the past 11 months. If we take it that it cost us 8c per kWh that's €70.80. It would take 15 years for the battery to pay for it self if it cost €1000. And your battery might last to 10 years if you are lucky.

My advice would be to forget about the battery.

Unless you live in an area where there is a high volume of power outages??

jim-osullivan

Haven't got a battery yet but wondering how do you set it to charge say between 2am and 4am.

con747

https://www.boards.ie/discussion/comment/120569259#Comment_120569259

There are settings in the inverter for set charging times, plenty of YouTube videos on it if you google it.

jim-osullivan

Thanks for your advice con747.

Found this helpful youtube

videoSolis Hybrid Inverter - Self-Use with Time Charging - YouTube

Baoithin66

https://www.boards.ie/discussion/comment/120557275#Comment_120557275

Hi could you also pm details of where you got the batteries. thanks

Scoopsire

https://www.boards.ie/discussion/comment/120557275#Comment_120557275

Hi could you pm the details of where you got the batteries please cheers

the_amazing_raisin

PMs sent

I'm going back to my installer and asking for a referral bonus, I feel like this is the fifth time I've sent their details on

(I'm joking of course, I'm not affiliated with them and if I was I'd tell ye before I posted 😁)