Solar panels and battery - any real world recommendations?

Bloody hell, you lucked in to a cracking deal if you found a house with a 6kW system and a V2 powerwall installed!

Using the powerwall in the evening/night is what I plan on using it for. You say the impact is 50%... do you use a lot of electricity? I'd have thought the powerwall would have covered all of your evening usage.
 
ci_newman said:
Do you already have a smart meter fitted, and if so can you get daily / hourly figures from it?

The first thing you need to do is actually work out your daily / hourly usage for the last 12 months (at the very least, your energy bills should give you a monthly breakdown) then use those figures to see how much you'd be paying on an Eco7 rate + battery versus the current variable (and predicted rate rise in October) costs.

If you're excluding solar for now, the calculations are actually very simple because you know how many kWh you use already, and you're just looking at the Eco7 rate of 7.5p/kWh versus the ~47p/kWh predicted for October.
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I've not even finished buying the house yet :D it doesn't have a smart meter presently (which seems odd for a 2017 build) so that is the first port of call as I want to get on GO.

We have bills from our last house which will have very, very similar electricity usage, except I'm throwing on an EV now. Usage was about 2600kWh/year at the last house, so I've estimated 2500kWh day usage, and 500kWh night usage (shifting washing machine and future dishwasher to night time running) as a worst case scenario, plus chucking on 1100kWh further night usage for my EV (about 4000 miles at 4mi/kWh + 10% losses).
  • 2500/365 = 6.85kWh/day average
  • Differencing GO rates of 32.5/7.5 is 25p/kWh, so 2500 * 0.25 = £625/year saving if I can get all day usage onto a battery charged at the lower rates. Our average usage suggests this'll be possible if I size the storage well.

Who is doing Eco7 at 7.5p at the moment? I've only seen that low on Octopus GO for 4 hours.
 
squerble said:
I've not even finished buying the house yet :D it doesn't have a smart meter presently (which seems odd for a 2017 build) so that is the first port of call as I want to get on GO.

We have bills from our last house which will have very, very similar electricity usage, except I'm throwing on an EV now. Usage was about 2600kWh/year at the last house, so I've estimated 2500kWh day usage, and 500kWh night usage (shifting washing machine and future dishwasher to night time running) as a worst case scenario, plus chucking on 1100kWh further night usage for my EV (about 4000 miles at 4mi/kWh + 10% losses).
  • 2500/365 = 6.85kWh/day average
  • Differencing GO rates of 32.5/7.5 is 25p/kWh, so 2500 * 0.25 = £625/year saving if I can get all day usage onto a battery charged at the lower rates. Our average usage suggests this'll be possible if I size the storage well.

Who is doing Eco7 at 7.5p at the moment? I've only seen that low on Octopus GO for 4 hours.
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Yep, pretty much the only option if you're using battery storage is Octopus GO at the moment :) naturally that means you need to make sure your battery system has an inverter big enough to be able to charge it during those 4 hours.
 
ci_newman said:
Yep, pretty much the only option if you're using battery storage is Octopus GO at the moment :) naturally that means you need to make sure your battery system has an inverter big enough to be able to charge it during those 4 hours.
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Yep! Does having the higher inverter size cause DNO issues (extra application), or is that only when you're ready to export? Keep seeing a limit of 3.68kW on a few websites and discussions.

The master plan is:
  1. Stage 1 - Vanilla house on GO, with EVSE connected to grid directly.
  2. Stage 2 - Battery storage added, running all daily household load, with EVSE still connected directly to grid only.
  3. Stage 3 - Add PV. Same setup as above, except solar can now power house, trickle charge battery, trickle charge car, or export to grid.
That looks about right doesn't it? I'm planning now as I need to make sure I choose an EVSE that could accept solar trickle charging in the future but grid-only for now as I need the EVSE straight away.


EDIT: On the battery/inverter size - I suppose it would really be a case of can the daily usage be recharged in that period? If the battery is 12kWh but I'm only using 7kWh/day, then I just need to make sure that 7kWh can be replenished in the 4 hour window, which at 3kW charging should be easily attainable in a 4 hour window, even with losses.
 
I'd consider / think about how long these cheap night tariffs are going to last, with more people getting electric cars and house battery's the demand for energy during that period is going to increase quickly, therefore any payback period for a battery may be even longer.
 
squerble said:
Yep! Does having the higher inverter size cause DNO issues (extra application), or is that only when you're ready to export? Keep seeing a limit of 3.68kW on a few websites and discussions.

The master plan is:
  1. Stage 1 - Vanilla house on GO, with EVSE connected to grid directly.
  2. Stage 2 - Battery storage added, running all daily household load, with EVSE still connected directly to grid only.
  3. Stage 3 - Add PV. Same setup as above, except solar can now power house, trickle charge battery, trickle charge car, or export to grid.
That looks about right doesn't it? I'm planning now as I need to make sure I choose an EVSE that could accept solar trickle charging in the future but grid-only for now as I need the EVSE straight away.
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DNO is only relevant for exporting :)
 
Firestar_3x said:
I'd consider / think about how long these cheap night tariffs are going to last, with more people getting electric cars and house battery's the demand for energy during that period is going to increase quickly, therefore any payback period for a battery may be even longer.
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Yep, the whole of the battery saving/payback period is reliant on the difference of day and night rates. If the difference drops or the night rate disappears then the saving drops or becomes non-existent. Well, at least for a battery-only install. If you can trickle charge from solar you'll still make great savings over summer I should imagine, plus stored energy in case of power cut.
 
EVH said:
Bloody hell, you lucked in to a cracking deal if you found a house with a 6kW system and a V2 powerwall installed!

Using the powerwall in the evening/night is what I plan on using it for. You say the impact is 50%... do you use a lot of electricity? I'd have thought the powerwall would have covered all of your evening usage.
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I’ve been around property most of my life thanks to my late father so I know when I see something that’s worth it.

I think the impact reduction due to the Tesla energy plan is because it sometimes can pull from the grid. It’ll normally depleat to 20% from a 100% on this plan when exporting. When I used it on the other tarrif I found it would only depleat to 50-60%. So come October I will have to see if I plan to stay on this tariff.

We don’t use a lot of electric at all. Circa around £40-50 last month (including pulling from grid). Which from export we got £30 back.

The thing with the tesla energy plan is I cannot use the powerwall in the evening. It can only be done on the other tariffs. So we now use our domestic appliances during the day. Using solar power - then everything else is exported during the evening. Then it pulls back from the grid around 0.2-0.3kwh from 7pm to around 7amish when the solar starts pulling 0.2kwh from the sun (if we have any).

I’ll try post some screenies up from the app later this evening to give a better insight.
 
Firestar_3x said:
I'd consider / think about how long these cheap night tariffs are going to last, with more people getting electric cars and house battery's the demand for energy during that period is going to increase quickly, therefore any payback period for a battery may be even longer.
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Thats the really tricky one.

Long term the plan is to move to variable pricing, in order to try to reduce demand at peak periods. As such you would want to have a battery that is smart enough to be flexible in its approach.
Eg if the peak is super high and they also move exporting rates to variable you may be better dumping all your charge, and either paying to draw from the grid, or recharging later

This is all part of the plan. To enable the grid to be more flexible and make it worthwhile for people to export to the grid when prices are high, helping to load balance and reduce the need for higher and higher minimum grid generation.
(Renewables have a low % of minimum so unless we want brown outs you cant take averages)
 
Firestar_3x said:
I'd consider / think about how long these cheap night tariffs are going to last, with more people getting electric cars and house battery's the demand for energy during that period is going to increase quickly, therefore any payback period for a battery may be even longer.
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100%, it's a lot of eggs on a basket if the supplier pulls the plug (excuse the pun) on cheap night rates as more and more jump on the band wagon.
 
Hmmm, makes me want to stick with Octopus Go for my EV and make sure I try to only use the powerwall energy in the evenings. Is this possible? (i.e. telling the system to use from the powerwall before I goes to the grid?)

The highest cost per day should be offset by the solar generation.
 
EVH said:
Hmmm, makes me want to stick with Octopus Go for my EV and make sure I try to only use the powerwall energy in the evenings. Is this possible? (i.e. telling the system to use from the powerwall before I goes to the grid?)

The highest cost per day should be offset by the solar generation.
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From what I've seen online, you can set the Powerwall to a TOU setting? However, that may not be an option if you're on the Tesla plan? Also I guess that'd only work to make it charge in the cheap period, it wouldn't force usage to the evening. It'd just be any time other than the cheap time.
 
Been quoted £4700+VAT for the GivEnergy 3kW AC inverter and 8.2kWh battery installed. However, there is a long wait and unlikely to be installed until August.

Already have solar with my house, details below:

  • Type: PV
  • Number of panels: 8
  • kW per panel: 0.26
  • Total kW: 2.0
  • Generation Meter: Elmlite
  • Generation Meter model: ECA2 V
  • Installed by: Eco2solar
 
Mercenary Keyboard Warrior said:
Thats the really tricky one.

Long term the plan is to move to variable pricing, in order to try to reduce demand at peak periods. As such you would want to have a battery that is smart enough to be flexible in its approach.
Eg if the peak is super high and they also move exporting rates to variable you may be better dumping all your charge, and either paying to draw from the grid, or recharging later

This is all part of the plan. To enable the grid to be more flexible and make it worthwhile for people to export to the grid when prices are high, helping to load balance and reduce the need for higher and higher minimum grid generation.
(Renewables have a low % of minimum so unless we want brown outs you cant take averages)
Click to expand...

I believe GivEnergy (and maybe Tesla Powerwall) will work in tandem with Octopus Agile - they can download the next 24 hours of prices and adjust accordingly, so could charge overnight and early in the morning and have enough capacity ready for that 16:00-19:00 peak period. But yea, using a "dumb" battery storage needs the cheap period and is entirely reliant on it (at least for the financial part - if you want it for reasons of not using the grid in the dirty period then you may care less about the payback/breakeven).

EDIT: GivEnergy link - GivEnergy
 
94JDH said:
Arghh missed it off £14k


It's the new gen2 one still at 3.6kW each but the benefit for me is that each gen2 can charge/discharge at 3600W up from 2500w on the last version.
If needed this gives a potential 7.2KW charge/discharge in this arrangement.
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That price seems really quite reasonable, especially as it's 18kWh storage in total, and 7.2kW output. I could 100% power all my daily usage on that!
 
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