Solar and battery solution ...or is there better?

bucksman

I am getting close to pushing the button on this system, we use around 4500kw a year and are based in Bucks.  This proposal gives an estimated 5.22kW: 12x435w Jinko Panels, 2x5.12kWh SunSync Battery, SunSync 5kw Inverter, Bird Barrier, 12xTygo Optimisers. This has 6 panels on the East and 6 on the west-facing roof, with scaffolding included £9500. Or should I go mad and use the notion of buy once and buy the best?  I have seen the responses before of mixed views about Sunsync batteries regarding DOD.

Thank you in advance for any thoughts or suggestions.

 

 

Screwdriva

I recommend buying reputed brands for maximum system longevity but I don't believe they should come at a significant premium. 

That said, I would never install Jinko panels on my roof, as they have historically degraded more than any other panel brand. Sunsynk is full of issues too (as you rightly point out). There are also serious ethical questions about Chinese owned brands, perhaps more relevant on these forums. 

For your consumption, unless you're planning on a heat pump or experience blackouts, I would recommend skipping the battery altogether and export your excess Solar PV generation via Octopus Flux instead, effectively using the grid as your "battery". I recommend this calculator to yield an approximation on return on investment with an inexpensive 5kW battery/ without a battery. 

For perspective, a superior spec system quote I've seen just this week below:

12 X Sharp 425W (30 year guarantee)
12 X SolarEdge optimizers 
  1 X 5kW SolarEdge inverter (20 year warranty)

£6200 installed. Bird netting and G99 included.

Reed_Richards

@Screwdriva always says that: "Don't get a battery, just export".  They are probably right if you don't mind signing up with Octopus and you're prepared to gamble that the current import/export price differential is maintained.  But the calculation differs if you are on a time-of-use tariff that allows you to charge your batteries overnight over the winter when solar power is less plentiful.

Screwdriva

Reed_Richards said:

@Screwdriva always says that: "Don't get a battery, just export".  They are probably right if you don't mind signing up with Octopus and you're prepared to gamble that the current import/export price differential is maintained. 

If you're going to misrepresent what I share, might I suggest an attempt to make it sound a bit more believable, given my previous post?  

There are scenarios where batteries do make fiscal sense. For example, if you have or plan on a heat pump/ experience blackouts or are on FIT. For nearly everyone else, the numbers simply don't add up. That said, if the Octopus tariffs suddenly disappear, one can always add a battery later VAT free, for less £ as prices are falling rapidly. 

If anyone likes the thought of having a battery despite these numbers, more power to them! I'll leave you with this post from another wise forum member. 

EcoScruples

I would agree, work it out properly without a battery, selling back to the grid will earn you back more money currently and also allow y9u to get a bigger system. Batteries are expensive and tend to break even at best.

I do love having the flexibility of a battery and really enjoy playing around with import/export but had I did a little more research I'd have gone without one and spent the money on more panels and bigger inverter.

ecraig

EcoScruples said:

I would agree, work it out properly without a battery, selling back to the grid will earn you back more money currently and also allow y9u to get a bigger system. Batteries are expensive and tend to break even at best.

I do love having the flexibility of a battery and really enjoy playing around with import/export but had I did a little more research I'd have gone without one and spent the money on more panels and bigger inverter.

Me too.
It’s a tough decision but I would’ve gone for 24 panels (instead of 12) and a bigger inverter. No battery (at the time of install)…
Nobody has a crystal ball to decide on these things at the time, and you never know what prices in the future will be offered for exporting.
one thing for sure is that battery prices are coming down and if i had a bigger array and subsequently wanted batteries at a later stage i would probably ask for mount rack batteries such as pylontech or a new brand on the scene which is fogstar..
both are cheap as chips as very expandable. You could easily add extra units yourself as a diy project as they simply plug and play (from what i can ascertain). 

By the way, OP, I have the same east and west setup as you.
My western panels yield me more, so perhaps look at 8 on the east and fill the west to the max. 

I also now have an EV, but I charge from the grid overnight and have no interest in draining my batteries to filll up the car, nor is it cost effective for me to charge the car from the solar array. The overnight grid price wins every time. 

Qyburn

Screwdriva said:
... You will be paid for your export of surplus solar PV at around 22p/kWh

Are you assuming power is all exported during the peak time 16:00 to 19:00?

Screwdriva

Qyburn said:

Screwdriva said:
... You will be paid for your export of surplus solar PV at around 22p/kWh

Are you assuming power is all exported during the peak time 16:00 to 19:00?

The original post I attached was shared last year by another forum member during a more lucrative Flux period. 

If 100% generation was exported during the 4-7pm window, one would earn ~25p per kWh. If 100% were exported outside of this window, ~16p per kWh. In reality, a blended rate of ~18p for export can be expected on Flux in Q2 '24. This often increases to well north of 20p per kWh, once self consumption is factored in.  

Reed_Richards

Screwdriva said:

...I'll leave you with this post from another wise forum member. 

This would be a more sensible quote if it actually mentioned the cost of the battery.  But we can infer that: 80p x 5000 = £4,000.  £4000 for a 3.2 kW (usable) battery.  The OP's proposed system will have 2x 5.12 kW hour batteries, perhaps that's 2x 4.6 kW = 9.2 kWh hour usable?  So that should cost £11,500 for the batteries alone.  Yet the OP's entire system will cost only £9,500.  It seems that battery prices must have fallen quite a lot since the time of that quoted calculation.  Which obviously begs the question, is the conclusion of that calculation still valid?    

bucksman

I really appreciate the input to this original post.  My plan, like so many, I believe, is to continue to charge the EV using cheaper electricity at night (with Eon, it's around 10p between midnight and 7 am) and at the same time to charge the battery and then use the stored power from the battery to run the house during the day.  We use around 8-10kwh on average daily (excluding EV charging) to run the house. Any solar will be used for the battery or to sell back to the grid. My research had indicated that the battery capacity should be increased, hence the x2 batteries.  Maybe some maths is required! Eon is offering at the moment around 15p for export. 

Screwdriva

bucksman said:

...and at the same time to charge the battery and then use the stored power from the battery to run the house during the day.  We use around 8-10kwh on average daily (excluding EV charging) to run the house. 

Some of us have shared that this approach may not make financial sense given the cost of purchasing and running a battery for this very purpose, as your consumption does not appear high enough to offset. (Charging the EV at night directly from the grid is more cost effective as you would not experience battery conversion losses).

bucksman said:

Maybe some maths is required! Eon is offering at the moment around 15p for export. 

Indeed. I'd give the calculator (linked above) a go. It allows for your precise use case. You can input generation, consumption and Flux import/ export tariffs for your area quite easily to get a precise estimation of return on investment.