A year with home Batteries (and more solar and an EV)

Solarchaser

I thought id make a new thread to share my experiences in the hope of giving a real world example of home batteries.

Ive had 4kw of sse panels for over 5 years.
I always had a hankering for batteries, and using a search engine i stumbled upon this forum and the discussion about home batteries.

Eventually after reading for over a year and humming and hawwing, and generally annoying myself, i though F*** it, im getting them!

In late 2018 i picked up a sofar me3000sp and 1 x 2.4kwh pylontech battery.
Both units were a year old at that point.
I then bought two more 2.4kwh pylontech batteries new so that i could use the full potential of the inverter, as each battery is capable of approx 1.25kw (25a) constant output, so to have the sofar charge and discharge at 3kw (60A) 3 batteries were required.
In the same journey to pick up the batteries, i also picked up a new growatt hybrid inverter with 4.8kwh battery and finally a new (to me) 24kwh nissan leaf.... not all at the same place.

I installed the sofar with 3 batteries at the start of Nov 18.
I installed the growatt hybrid at the start of Jan 19 to go with 6.6kw of panels on my garage roof in a 3.3kw wsw and 3.3kw ene configuration, both sides suffer from shading in the darkest 6 months, so i bought rec twin peak panels as a cost effective way of mitigating some of the shading.

I hadnt been logging my usage month to month before the sofar, noting it only every 3 months to co-incide with the FIT readings, and so to give a decent comparison to previous years, i had to wait till the start of Feb this year to have figures to compare.(november wouldnt have taken into account the solar panels)

So i think that pretty much sets the scene, the only note i have to add is that the growatt hybrid never worked properly, it would import and export when it felt like it, so ive discounted the fact it had a battery, as it was basically useless.
In May growatt took the inverter back and i bought a couple of old sma 3300 inverters to replace it.

So to the nitty gritty.
I paid:-
£750 sofar plus 1 battery
£1500 two pylontech batteries
£2500 for the growatt... which was then refunded
£1900 for 6.6kw of panels delivered
£250 for two 3300 sma inverters
£150 ish for solar cable. Isolators, crimps etc
So im around £4550 laid out at the start of last year.

Something i feel is very important for the sums to add up for batteries, is usage.
Imo if you buy less than 4Mwh a year, you are gonna struggle to justify them, but thats just my thoughts.

My usage for the past couple of years has hovered around 5200Kwh electric.
I was previously with EDF paying 13p/kwh and 25p / day standing charge coming to around £767 a year.

I moved to bulb last year, (edf were hiking prices) so paying 12.8p/kwh and 19.4p/day standing charge so should come to £739 a year.

(What i didnt realise was that i was actually paying more for my gas with bulb, and if i had just ran the same amounts, i would be paying an extra £70/year in gas, doh!!)

So with the EV, the annual mileage has doubled, as the wife loves it, never having to pay for fuel has been great, so she tells me.
The car has done 8k miles in the 16 months the vast majority charged from home.
However i did holiday in Englandshire last year which accounted for over 1k miles, and its sometimes charged elsewhere, so in the interests of better to under estimate than over, ill say around 4k miles have been charged at home, the leaf does a little under 4 miles to a kw, so i think adding 1000kw to my annual usage is about right (certainly not over estimating).

So if we assume my grid usage should now be 6200kw the cost should be ~£876 a year for electric.

So how much have i actually used from grid? 
3665kwh so £546 (inc daily charge) a saving of £330 a year. (From £4550 outlay)

So if all stays equal a just under 14 year payback.

Edited cos i forgot i had to buy replacement inverters, and i cant count😳

Solarchaser

The sofar i have tells me how much solar, how much consumption and how much grid usage, but it doesnt tell me the cumulative charge and discharge of the batteries.

The cycle count on the new batteries is 236 i think (sorry chamelion i said 200 yesterday) though i will confirm tomorrow when i rip out the sofar. (Confirmed, 236)

So i know the batteries have cycled out their 6kw 236 times so 1400kw of full cycles.
But it doesnt count how many times it charged to 80% or 90% and discharged, nor how many times it went from 100% to 30% and charged back up, only the amount if times it went from 15% to 100% and back to 15% (a full cycle).

I need more info.

I cant justify spending more money for roi, it just wont happen, but ive now spent a further £4500 on getting another 5 batteries and replacing the sofar with two Lux inverters to run in parralel, this will give the inverters an easier time, give me much better info, and cope with loads bigger than the 3kw max of the sofar, which has been an issue in the house, as my wife loves her white goods.

Its all parr of a process too, will soon be replacing the two year old gas oven with electric, and in the coming years moving to electric hot water and hopefully electric heating, so its better to have 7kw of battery power available... thats my story and im sticking to it.

My take on it, is that its partly about being greener, and its partly about being geeky, and its partly a cool wee project.

katyoxoo

what are people’s thoughts on these buy your fit payments schemes . We are on the top
 rate and are already in profit with the installation costs 

Solarchaser

Thought id add some more figures as ive been trying to figure out how much of my "saving" is the batteries, and how much is the extra solar.
So this is all very much on the fly.

So i had a smart meter fitted end of feb 2017.
Its showing export of just over 6050kwh, this is excess solar ive sent to the grid.
From the sofar data, last year accounted for 2550kwh, so the previous two years are around 1750kwh each. (No sofar then, so just a semi-educated guess)

My fit system generates around 3200kwh every year, so from this, the deemed 50% export is there or thereabouts (1600) for pre battery generation / usage.
This means my 5200 bought electricity plus 1600 solar usage brings actual consumption to 6800kwh / year pre batteries car and solar.

Fit system for 2019 had lowest ever solar production at 3100, but total generation is 7300, meaning the new array  generated around 4200kwh last year
So 7300 - 2500 export = 4800 solar used plus the 3665kwh of bought electric indicates my usage has increased to 8465, an increase of 1645kwh instead of the 1000kwh i plumped for.

Unfortunately while some of these figures come from the smart meter, most are from the sofar, and although when ive done direct comparisons between sofar and smart meter, the sofar has been no more than 5% adrift (pretty good for ct clamps) i feel its worth noting there is a fudge factor.

Using purely the sofar figures for 2019
Solar 7310
Export 2510
Bought 3540
Consumption 7870

So solar minus export, plus bought should equal consumption, but it doesnt.
7310-2510+3540 = 8340, not the 7870 its telling me a difference of 470... which is around 5% i suppose.

And actually taking the lower figure... purely cos its suits me, the 7870 is an increase of just over 1000kw of consumption for the addition of the car right enough.

So i think im right in saying, for as far as i can believe these fudgey figures, that in previous years ive managed to use around 1450kwh of my solar production, but in the last year ive managed to use 4800kwh, an increase of 3350 (saving of £428).

Some of that will be deliberately plugging in the car once i seen the batteries were full, but honestly, maybe 40% of the car charging at absolute best, (more likely 10%) so you could take 400kwh off that, say instead an increase of 2950, times 12.8p is a saving of £377

Im looking forward to the coming year where i will have 8 batteries instead of 3, 90% dod instead of 80-85%, and making full use of octopus Tou tarrifs in the winter both for battery and car charging.

It would / will be really nice to both increase my self consumption and reduce what i pay for the grid bought kwh.

I hope my meanderings have helped someone.
They have helped me get my brain round it.
Probably made the case that batteries are unlikely to pay for themselves tbh, but i think it helps to show they arnt a total waste of time / money either.

I know ive said this a few times, but its hard to understand just how satisfying it is, when your house has ran all day, through the dinners for 6 people and 5 loads of washing and its cost you only 2kwh, instead of the 20 it would have cost without solar / batteries

Solarchaser

You know sometimes you think a post will attract a good discussion, comparison of figures, interogation and theories.
I thought this would, as theres at least half a dozen with batteries, but instead ive ended up like troll ape talking to myself in multiple posts.
😂😂

Martyn1981

Solarchaser said:

You know sometimes you think a post will attract a good discussion, comparison of figures, interogation and theories.
I thought this would, as theres at least half a dozen with batteries, but instead ive ended up like troll ape talking to myself in multiple posts.
😂😂

New puter, who dis?

Screwdriva

Really useful data. We have a Solaredge HD Wave 3680 inverter with 10X400W LG BiFacial panels, each with an SE Optimizer. I resisted the urge to install batteries till we purchase an EV, with the belief that batteries will continue to improve over the next few years. 
For newer installs like mine where we lack the FIT tariff (SEG is a joke!), minimizing cost while maximizing yield seems to be the way to improve ROI these days.

mickyduck55

Martyn1981 said:

Solarchaser said:

You know sometimes you think a post will attract a good discussion, comparison of figures, interogation and theories.
I thought this would, as theres at least half a dozen with batteries, but instead ive ended up like troll ape talking to myself in multiple posts.
😂😂

New puter, who dis?

sorry but only had them a few weeks LOL

JKenH

Solarchaser said:

You know sometimes you think a post will attract a good discussion, comparison of figures, interogation and theories.
I thought this would, as theres at least half a dozen with batteries, but instead ive ended up like troll ape talking to myself in multiple posts.
😂😂

Well, you are inviting questions so here goes. 

I see you have in excess of 10 kwp and 17 kwh of storage; did you have any difficulty with getting approval from your DNO?

Solarchaser

Any difficulty, no.
Have i asked them... also no.

Maybe ill be the test case for a conviction for too much solar??

chamelion

Ugh. I really want to join the club. Despite your posts (conversation with yourself lol) clearly articulating this is unlikely to pay for itself in any reasonable time frame. 

I've decided, for my own sanity, that if I can get a LUX 7.2kwh setup for under 3k (self fitted) I'll jump. Current price with the DC switch is about 3200-3300 shipped. 

Let's see how this works out!