On-grid domestic battery storage

Exiled_Tyke

I reckon it's still about 10p for me.    I paid £3k for my 6.3kWh Solax.    I reckon this started life as about 5kWh useable (also taking into account round trip losses).  The warranty is 10 years and an estimate of over 6,000 cycles.  I'll generously go with 6,000 cycles. This means 1.6 cycles a day which as I charge at night and from PV is probably fair.   I make this a total of around 30,500kWh saved over the life of the battery.   So what previously looked like a vanity project now finally looks like it may possibly be financially viable.

newbuilder

I assume that if you are adding to it in off peak then you need to add the unit rate too but with unit rates of peak at about 25p then it is still making money?

Starfrog

Martyn1981 said:

Can I ask a general question / bit of advice?

Way back at the start of this thread I think I calculated that the cost of storage was about 10p/kWh*. It wasn't a fair estimate, but just an early one for reference. I used a Powerwall II, and based it only on the warranted cycles (at the time). I think I explained that I wasn't trying to be overly hard, just taking an early days position till we'd had more experience of batts, and how well they lasted.

*I divided the cost by the number of kWh's, which in turn was based on the sensible useable amount of capacity times number of cycles, times again by 90% to represent an average capacity slowly dropping to 80% over that time period. I don't know if that is still considered the best/reasonable way to calculate it?

So now that so many of you have batts, that seem to be working really well, and are paying far less (per kWh) to buy them, and it seems the expected cycles have risen(?) what would be a fair estimate for the cost of domestic sized storage now .... 5p/kWh ..... less .....?

Thanks for any advice.

For what its worth the way I looked at the costs for my batteries was to just take the amount of power I got from the batteries that I didnt have to pay for power from the grid (simplistic but in my mind the right way to look at the ROI) so for me last year I got 1336kWh of battery power and at the rate of 0.32p = £427  that was from 2x2.4kWh (4.8kWh in total capacity) so if I look at the average cost of a two plyontech batteries giving me 4.8kWh it is £770 per battery so £1540 for two. By that measure the payback would be 3.6 years and as the optimum life time Is around 12 years (i assume a cycle of once a day for 4500 days) then that leaves me with at least 8.4 years of benefit of which is a saving of £3586 over the years but then that is at 0.32 per kWh and I think we all know that the price of electricity is only going to go up so the ROI and the benefit just make sense to get battery storage with any solar panel array that is producing more than you can possibly use while the sun is shining ! I think the increase in electricity for everyone makes Solar even more of a sensible thing to do the ROI is breaking even much more quicker.

JKenH

That calculation is fine if you are doing a d-i-y addition to an existing battery system but for a new installation you need an inverter and for most people there will be racking, cables and labour for installation and profit to add. It’s a bit like calculating the cost of solar PV based purely on the cost of buying the panels from a wholesaler.

Edit: and you may also have DNO costs to consider. 

Edited again to show the post I was replying to.

JKenH

I wanted some back up power for emergencies and having failed to get past the DNO opted for a very simple stand alone solution. The cost is around 60% more than a pylontech battery but includes an inverter and facility for direct charging from a solar panel. I have ordered a 330w panel just to power the PPS. Once I get a mounting frame made I can track the sun to get optimum generation and should be able to recharge the PPS in around 8hrs on a good day. 

I used it to cook my toast this morning.

https://www.onbuy.com/gb/poweroak-bluetti-portable-power-generator-2400wh-solar-power-station~c9279~p52358177/

Martyn1981

EVandPV said:

Hi Mart, purely based on the cheapest deal currently for new Pylontech batts, not including an inverter and if I'm reading your calculation right >

2.4kwh x 90% = 2.16kwh x 90% = 1.94kwh

£750 / 1.94kwh = £386.60 / 6000 cycles = £0.06

Many thanks. Nice to see the batt part coming down. I assume that a major problem currently is the sheer demand for batteries, be it stationary of vehicular.

Looking at Wright's Law / technology learning curve, it seems for batts it's very high with estimates between 18% and 28% for every doubling of production. Just spit balling but if production can double 3x in the next 5yrs(?) then with just a 20% learning curve, that £750 price could become £384. All very promising.

[Obviously I'm ignoring the current world upheaval and hoping it all settles down asap.]

Martyn1981

Martyn1981 said:

EVandPV said:

Hi Mart, purely based on the cheapest deal currently for new Pylontech batts, not including an inverter and if I'm reading your calculation right >

2.4kwh x 90% = 2.16kwh x 90% = 1.94kwh

£750 / 1.94kwh = £386.60 / 6000 cycles = £0.06

Many thanks. Nice to see the batt part coming down. I assume that a major problem currently is the sheer demand for batteries, be it stationary of vehicular.

Looking at Wright's Law / technology learning curve, it seems for batts it's very high with estimates between 18% and 28% for every doubling of production. Just spit balling but if production can double 3x in the next 5yrs(?) then with just a 20% learning curve, that £750 price could become £384. All very promising.

[Obviously I'm ignoring the current world upheaval and hoping it all settles down asap.]

Two apologies:

1st - Taking this thread off course a tad by raising commercial costs.
2nd - Replying to myself.

But my reply reminded me of the pricing that came out last year for Megapacks, which does project a nice cost reduction, suggesting perhaps that the cost/kWh of commercial scale storage is, perhaps, half. Fingers crossed may it continue.

With 10 Megapacks, Tesla lists a price of $9,999,290, which results in a price per kWh of $327.87.

However, that’s not an accurate representation of Tesla’s battery costs since it also includes 7.6 MW of power inverters and installation.

Tesla describes the installation process of the Megapack:

1. Project design (including electrical and civil)
2. Project permitting (ministerial only)
3. Project construction (including electrical up to 480V, grading and foundations, mv transformer as applicable)
4. Project commissioning
5. Backup capability for critical loads

The price per kWh goes down as you order more Megapacks. 100 Megapacks brings the cost down to around $280 per kWh.

The configurator also reveals an annual maintenance cost, which escalates at 2% per year.

Tesla reveals Megapack prices: starts at $1 million

1961Nick

My pylontechs degrade about 1% for every 200 cycles. On this basis it’ll take 6000 cycles to reach 70% which is 1500 cycles better than the guarantee.

(849 cycles to date)

Verdigris

I think LiFePo batteries will have better lifetimes than was originally predicted. Batteries in EVs are now expected to last the reasonable life of the car.

Solarchaser

1961Nick said:

My pylontechs degrade about 1% for every 200 cycles. On this basis it’ll take 6000 cycles to reach 70% which is 1500 cycles better than the guarantee.

(849 cycles to date)

I wonder if you are straining them more than I am?
Not seeing any percentage difference from when I tested mine last year at this time.

Mine don't cycle every day and I have 4 connected to both inverters so less strain per battery.

Similarly due to a fairly large solar array and a fairly large daily consumption,  I'm finding that for every complete full to complete empty cycle, I'm having another couple of half cycles, and so as the 6000 cycle warranty is full to empty, I'm looking at more like a 12000 cycle warranty.