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Storage at home for solar panels and electric car

edited 30 January 2020 at 4:14PM in Green & Ethical MoneySaving
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pgoncalvpgoncalv Forumite
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edited 30 January 2020 at 4:14PM in Green & Ethical MoneySaving
Now that the FIT scheme is closed to new installations, electric cars are becoming more widespread, and battery storage is becoming cheaper, it makes sense to incorporate storage to match consumption with production or enabling purchase of electricity at cheaper rates.

I am lucky to be able to access TOU/30 minutes pricing from my supplier (as soon as I get a smart meter installed). Actually there's a good thread with info on it at https://forums.moneysavingexpert.com/showthread.php?t=6004585&highlight=flat

I am looking to size my PV system appropriately so it can cater for EV, aircon in summer and to be able to buy electricity at cheaper overnight rate, specially in winter.

Do any of you have experience or advice regarding storage capacity and good models? I saw that some of the battery systems last 6000 charges, I assume this means close to 20 years so a long timeframe to consider.

I saw a battery system with 4.8 kWh offer for supply and installation for £3000, so thought this may pay off. It lasts 6000 cycles with 80% discharges:
1 x SoFar ME 3000SP energy storage inverter
2 x Pylon Tech US2000B 2.4kWh lithium battery

I need to do some calcs to see if these are suitable. My current estimate of consumption is 3.4gWh / year (no aircon nor EV) - this is 9.3kWh per day
I am paying a daily flat electricity rate (variable from day to day but currently 12p/kWh)
I read somewhere that a PV panel system of 1kw produces 850kWh per year in the UK. I am just north of London so hope it could produce more than average.

Replies

  • Exiled_TykeExiled_Tyke Forumite
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    My 6.3Kwh Solax cost around £3000 installed (priced with no VAT). very happy with it so far
    Install 28th Nov 15, 3.3kW, (11x300LG), SolarEdge, SW. W Yorks.
    Install 2: Sept 19, 600W SSE
    Solax 6.3kW battery
  • rugbyleaguesmaterugbyleaguesmate Forumite
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    This question is exactly the same as I want answering lol! I've got a quote for £4000+installation for an 8.7kw Battery and wondering whether to push the button. My solar system is in my signature and I run an electric car.
    6.72kw Pv Ja Solar 280w * 24 panels, Solar Edge inverter, South facing no shading.
    South Lake District, delightful view of Morecambe Bay. Not Saving up for a battery too expensive:j:mad::hello:

    July Solar target 769kw
  • ABrassABrass Forumite
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    When do you think you will be able to charge your EV and how many miles a week do you expect to do? If you can often charge during daylight hours then the battery will be independent of the EV for cost savings.

    If you'll have to charge later in the day or overnight then the battery may be useful for that, or it may be better to conserve the battery for evening and morning use and charge it and the EV overnight on cheap off peak power.

    The difficulty here is there's so many moving parts that will decide if you'll save money with a battery or not.

    Also, assume you will want to change your electricity supplier. Flat rate charges don't work that well with batteries and there's a very good chance your current supplier only pays a pittance for SEG.
  • rugbyleaguesmaterugbyleaguesmate Forumite
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    ABrass wrote: »
    When do you think you will be able to charge your EV and how many miles a week do you expect to do? If you can often charge during daylight hours then the battery will be independent of the EV for cost savings.

    If you'll have to charge later in the day or overnight then the battery may be useful for that, or it may be better to conserve the battery for evening and morning use and charge it and the EV overnight on cheap off peak power.

    The difficulty here is there's so many moving parts that will decide if you'll save money with a battery or not.

    Also, assume you will want to change your electricity supplier. Flat rate charges don't work that well with batteries and there's a very good chance your current supplier only pays a pittance for SEG.

    Sorry for hijacking this post a bit, I think expecting PV to charge the car is not realistic, it might help a bit but difficult to time the sun and the car to be at the right place at the right time.

    My reasons for a battery is that pre EV my household consumed 12kw's per day which for maybe 8 months of the year my solar system easily produces but then it goes to the grid because I can't consume it.

    My logic is that if I get a battery that I charge with excess Pv and cheap overnight electricity then it could pay for itself and help the environment?

    In big handfuls I want as many Kw's that we produce to be used rather than just receiving 5.5p for them from Octopus.
    6.72kw Pv Ja Solar 280w * 24 panels, Solar Edge inverter, South facing no shading.
    South Lake District, delightful view of Morecambe Bay. Not Saving up for a battery too expensive:j:mad::hello:

    July Solar target 769kw
  • SolarchaserSolarchaser Forumite
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    On ebay there is an offering for the system you describe for £2600 installed.
    Sofar me3000sp and 2 pylontech batteries.

    I have this system with 3 batteries.

    Tbh there is alot to say, and I could prattle on for a while about it.

    I think the cost of pylontech at least had basically stagnated or increased over the last 18 months.
    I got fine for £750 per battery and cant get them cheaper anywhere now, so I'm not seeing the cost come down.

    At 80% did they are good for 6000 cycles (likely much more tbh) so the 4.8 you would buy is only 4kwh useable.

    I've used mine purely for solar storage, not overnight charging, and from top of my head they have done 230 full cycles in the 15 months I've been running them.
    At 7.2kwh (6kwh useable) it's not worthwhile for me to switch to a tou tariff, as the house averages 20kwh /day.
    So for me the answer is to increase the amount of storage to then make it worthwhile (hopefully ebay winnings turn up tomorrow)

    The sofar charges and discharges at a max of 3kw, that's important because not many do that high output.
    That will cover an electric oven, or a standard kettle.... it will also cover ev granny chargers.

    I think the solax is 2.5kw, I'm sure the early moxias were something silly like 500w. But you gotta hope they are better now.

    Something else to throw in is efficiency, if you charge the 4kwh battery, it will cost you more than 4kwh, and when you discharge the 4kwh battery, you wont be able to use 4kwh, as some gets lost both ways in the inverter converting ac /dc then dc/ac.
    Round trip efficiency is rarely above 90%

    Theres alot of reasons not to get home batteries.
    But the satisfaction of sitting on a summers evening running the house for free on solar you generated earlier that day, cant be understated, its supremely satisfying
    West central Scotland
    4kw sse since 2014 and 6.6kw wsw / ene split since 2019
    24kwh leaf and Lux 3600 with 17kwh useable storage
  • Exiled_TykeExiled_Tyke Forumite
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    The manual for my Solax (6.3 kWh0 Battery claims a roundtrip efficiency of 95% although I expect inverter efficiency needs to be taken into account on top. Also it claims 6,000 cycles at 100% DOD (I find this surprising) at 25oC. It is set to discharge to 10% although once in a while drops to 5% and then immediately starts to recharge back to 10% (from import). I'm guessing this is part of the Battery Management System's programme to calibrate or manage the battery life in some way.
    Install 28th Nov 15, 3.3kW, (11x300LG), SolarEdge, SW. W Yorks.
    Install 2: Sept 19, 600W SSE
    Solax 6.3kW battery
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