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Author Topic: Solar Battery, PV and Eco Rate Electrickery  (Read 4807 times)
NugentS
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« on: May 05, 2019, 07:47:18 PM »

All,

Back in 2012 (I think it was) I put 4Kw of Solar PV (Sanyo HIT's) up on my roof. Cost was approx 11K (I found a receipt), has consistently overachieved the official production figures and I am very very pleased with it. I haven't counted, but it may even have paid back (the gross figure anyway). It is a well worth it investment. I was happy with anything between a 7-12 year payback and it will easily achieve that (disasters not withstanding and as long as those effing pigeons just b$^^er off)

I use a lot of power 24*7 due to computer equipment running 24*7, had disk drives etc all of which costs quite a lot of money every month.

I also have an EV (albeit a small one) (for about 3 weeks now)
I am currently switching to Octopus Go. The car takes about 4 hours to charge from flat on a 16Amp charger and Octopus go gives a 4 hour cheap rate at 5p/minute - which all seems a no-brainer

For a while now I have been looking at battery systems - but they just haven't made sense financially, either too small, or too expensive or both.

However I have just gone over my man maths - and have a large spreadsheet that says I can save £435 a year (possibly a bit more) by putting in a large enough battery. I am assuming a battery with 11kWh of useable capacity. The battery would charge during the cheap rate, and when my solar output exceeds my usage. On a very good day I would still export power and on bad days I would obviously import. The numbers almost work - close enough that all other questions being answered correctly, and my maths being correct I am prepared to pull the trigger on this one. Payback in the region of 10-12 years is what I am looking for.

Does anyone have any thoughts / advice / comments

Do Navitron do battery systems?

Regards

Sean




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RIT
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« Reply #1 on: May 06, 2019, 12:01:42 AM »


Do Navitron do battery systems?

Regards

Sean


It would be best to just give them a call as there is very little on their website apart from a few PV inverters with builtin chargers.


As for your figures with the detail you have provided you seem to be expecting to cycle the batteries daily. Only you can know if you will manage to do this, considering 4 hours of the day you will have access to low-cost power from Octopus and during the daytime, the PV will be providing you power.

If you do not manage a daily cycle your payback period will lengthen. One comment I make to anyone who plans to install batteries is that you have to factor in 2 other things when calculating the payback.

   - The money could be earning interest - so even at today's poor rates it is something to take into account.
   - In general, the cost of battery storage has been falling every year. So you should take into account the cost of doing something today compared to waiting.

The other question is how much more efficient can you make your IT environment if you instead invested in that? I once had a fair stack of servers, but in the end I virtualized them to a single system and replaced all the 24x7 spinning rust with SSDs. The NASs I owned only started up when the backups were due to run. I ended up with a 80% power saving and a much quieter environment.

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2.4kW PV system, output can be seen at  - https://pvoutput.org/list.jsp?userid=49083

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linesrg
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« Reply #2 on: May 06, 2019, 07:22:12 AM »

Sean,

You quote an annual saving figure of £435 per annum and we have to assume you have factored everything in.

You will see from postings elsewhere that whenever the Octopus Go tariff comes up I have always been somewhat sceptical of any claims they make but I'm prepared to accept that if you can maximise their cheap periods then you might make some savings but I have found that taking the charges they make at other times of day outweigh any advantages.

Generally speaking, for the majority, I don't yet think there is a financial case for installing batteries.

Yes I've done it and discovered, when you add everything up (and I'm sad enough to do that), that even with a 'cheap' install using second hand equipment, where possible, the sums probably still don't add up.

The best I can say about mine is that it makes me feel better and overall it is reducing my impact on the planet.  (Do SMA quote figures for when their pieces of equipment become 'carbon neutral'?)

RIT's suggestion looks like it may be a more logical approach.

Regards

Richard
« Last Edit: May 06, 2019, 07:23:46 AM by linesrg » Logged

1.28kW on a Lorentz ETATRACK1000 + 1.44kW/ SB3000TL-21 (FIT), 1.28kW/ SB1700 (ROO/FIT). CTC GSi12 heat pump/Ecosol/Flowbox 8010e/Gledhill ASL0085 EHS/3off Navitron 4720AL Solar ET & Immersun T1060/T1070/T1090. 3.375kW/ SMA SB3600TL-21 and a Sunny Island 4.4M-12 c/w 15.2kWh battery and a Renault Zoe.
Stig
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« Reply #3 on: May 06, 2019, 07:50:16 AM »

Another thing to check would be the small print of your Octopus Go tariff - is there a minimum day/night ratio or will they really let you run 100% of the cheap rate with no daytime usage?
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dan_b
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« Reply #4 on: May 06, 2019, 09:12:00 AM »

Did you use my referral code to switch to Octopus? That would give you an extra £50 to play with  laugh
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3.06kWp SolarEdge system with a split array:
2.18kWp 10x South facing, plus 4x West facing 880W

Mk1 ImmerSUN DHW diverter
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dan_b
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« Reply #5 on: May 06, 2019, 09:15:26 AM »

Here it is

https://share.octopus.energy/teal-leaf-367
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3.06kWp SolarEdge system with a split array:
2.18kWp 10x South facing, plus 4x West facing 880W

Mk1 ImmerSUN DHW diverter
4kW PowerVault Battery

Tesla Model 3 Long Range
NugentS
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« Reply #6 on: May 06, 2019, 09:16:51 AM »


Do Navitron do battery systems?

Regards

Sean


It would be best to just give them a call as there is very little on their website apart from a few PV inverters with builtin chargers.


As for your figures with the detail you have provided you seem to be expecting to cycle the batteries daily. Only you can know if you will manage to do this, considering 4 hours of the day you will have access to low-cost power from Octopus and during the daytime, the PV will be providing you power.

If you do not manage a daily cycle your payback period will lengthen. One comment I make to anyone who plans to install batteries is that you have to factor in 2 other things when calculating the payback.

   - The money could be earning interest - so even at today's poor rates it is something to take into account.
   - In general, the cost of battery storage has been falling every year. So you should take into account the cost of doing something today compared to waiting.

The other question is how much more efficient can you make your IT environment if you instead invested in that? I once had a fair stack of servers, but in the end I virtualized them to a single system and replaced all the 24x7 spinning rust with SSDs. The NASs I owned only started up when the backups were due to run. I ended up with a 80% power saving and a much quieter environment.



I can absolutely cycle the batteries daily - my base load deals with that superbly. No issue whatsoever with that.
Interest is IMHO irrelavent at this stage (and available rates)
Yes batteries are falling in price - but I have found that if one keeps waiting for a better price then one never does anything. In 10+ years time batteries will be different. Solid State maybe, smaller, higher energy density etc. Who knows. Deal with that in 10 years time.

My IT infrastructure has 3 servers, 2 on all the time (I can't get it down to one - I have tried, the second server just uses too much CPU [Plex]) and one powered off for power savings / spare
3 NAS's (1 does iSCSI storage on SSD's) for VMWare, 1 does primary storage and the last only turns on for backups during the 4 hour period. I also have a 4th NAS belonging to a friends company they offsite backup to it during the 4 hour period after which it turns off. I charge them for that - so don't really count the electricity cost.

All setup in preparation for the new Tariff.

Note that my estimated saving is 435 in year one. If electrickery prices go up, so does my saving bringing the payback period down. Of course if Octopus vanish in a puff of smoke then things will get a little more difficult

Sean
« Last Edit: May 06, 2019, 09:27:18 AM by NugentS » Logged
NugentS
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« Reply #7 on: May 06, 2019, 09:17:34 AM »

Did you use my referral code to switch to Octopus? That would give you an extra £50 to play with  laugh

Sorry - I used someone else's.

Sean
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NugentS
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« Reply #8 on: May 06, 2019, 09:19:52 AM »

Another thing to check would be the small print of your Octopus Go tariff - is there a minimum day/night ratio or will they really let you run 100% of the cheap rate with no daytime usage?

I'll still have some daytime usage as I am not sizing for peaks - which are transient.

Sean
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Countrypaul
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« Reply #9 on: May 06, 2019, 12:48:54 PM »

Just out of curiosity, how long do Octopus gaurantee to keep this tariff? Could they suck customers in for a couple of years and then abandon it forcing users to accept a higher tariff or change supliers? If so how do you factor that (and teh going up in a puff of smoke) into calculations?
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NugentS
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« Reply #10 on: May 06, 2019, 01:40:32 PM »

Honestly I don't

If I worried too much about what might happen, again I would never do anything. I suppose I could always shift to an alternative E7 tariff. It would be unlikely to be as good but wouldn't be too bad.

Sean
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nowty
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« Reply #11 on: May 06, 2019, 02:05:10 PM »

Last year I was hopeful of getting a 6p cheap rate Economy 7 deal, when there were a few of them still available. But by the time I got round to having the E7 meter fitted, the cheap rates had gone up to near 10p.

The Octopus deal (5p /kWh for 4 hours) sounds good but there is a 25p per day standing charge which would reduce my savings to almost nothing. And now their website says,

"PLEASE NOTE: We’ve currently paused taking new smart installation appointments as we begin a more controlled SMETS2 rollout over the next few months. If you don't want to wait on one of our standard tariffs in the interim, we'd recommend delaying your switch until we've started taking appointments again."

So missed the boat there.

There is another similar deal with Scottish Power at 4.74p /kWh for 5 hours, seems fixed until Jan 2021, but you need to have an EV registered at your supply address and they seem to want their Standing Charge to be a closely guarded secret.
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 50+ kWh's.
Hot water storage of 15+ kWh's.
Storage heaters of 15+ kWh's.
EV BMW i3 (another 30+ kWh's of storage).
6kW+ Ground source heatpump.
310,000+ litres of water harvested from underground river.
kristen
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« Reply #12 on: May 06, 2019, 02:11:35 PM »

If electrickery prices go up, so does my saving bringing the payback period down

My Man Maths would also include that IF i already had Battery installed I was in better position to take advantage of some other opportunity in future e.g. TOU metering - whereas a new Rate coming along, and then it taking me X-months to get Battery and have it installed (assuming that I had Cash at that point), would mean missing the boat somewhat.

Will your battery be UPS?  That's one of the main reasons I want a battery - each 10 second power cut as something external trips/resets/reroutes takes drown all my IT gear and several minutes until it is upright - plus whatever work I lost
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NugentS
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« Reply #13 on: May 06, 2019, 03:57:04 PM »

I wasn't planning on UPS - no.

All my computer equipment (that matters) is on UPS power anyway and and is on programmed shutdowns if the power goes out. The grid is reliable where I live so UPS seems to be not required

Sean
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kristen
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« Reply #14 on: May 06, 2019, 04:14:49 PM »

I wasn't planning on UPS - no.

The piddly individual UPSs we have seem to have a lifetime less than power cut frequency, so I'll be happy to replace them with a more robust "whole building UPS", that also gets me lighting etc. and thus a better ability to actually work albeit not the "indefinite supply" of a generator (I do have generator socket on outside of building, and a change-over-switch, so in principle I cold run generator to allow PV to generate ... and replenish Battery ... but no idea if that is pipe-dream or possibility)

My supply is reliable, but we have a momentary outage often enough to be annoying, and then a "JCB went through the cable" 4-hour outage probably once every year or two - even I had done that, and taken out all my neighbours  whistlie

When we had the building rewired I wish I had had the foresight to separate "essential circuits" so I could more easily configure the building to run on reduce power
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