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Discussion Starter #1 (Edited)
And Over the next week, I'm monitoring time use of the high energy appliances (10kW electric shower, electric oven, Kettle, Dishwasher, Washing machine, Tumble dryer). I use approximately 35kWh per day as I do have four other adults living here.

The oven is used on the fringes and past 7 pm, as well as the ES solely in the morning. If it's clear that the appliances are not used between 4-7 pm, then I may as well go on the Octopus Agile tariff (Also have a ZS EV so can take advantage of charging).

Qs: Is it worth installing battery storage to further take advantage of the low (and even negative) rates overnight. Then, use the stored energy during that 4-7 pm period, always taking advantage of the lower night cost.

The reason why is because you can buy cheaper modular storage (+ inverter). Not sure about installation costs (are you allowed to install yourself or does it require a fully qualified electrician?).


I already understand that there'll be a limitation of battery discharge current, limiting me to 1.2kW per module. For a standard oven, it'll be around 2.4kW so need at least 2 to run the most likely device (I have gas-fired CH and hob).

So, am I missing anything? I'll check the results of the week and lets first see if the agile tariff makes sense...
 

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You'll need a lot of batteries to cope with your high consumption.

Maybe a few lifestyle changes made by the other adults would help more (reduced duration showers, air dried washing etc) would help in conjunction with a small amount of load time shifting.
 

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Have you calculated the time to get a return on your investment? Plunge pricing is rare historically, so it is best to limit the cost saving to the artificial 12p/kWh that Agile uses to disincentivise the peak period, and don't forget the 10% roundtrip loses. So for a 2kW unit you'll be saving around 20p a day for what investment by the time you've included the inverter?
The idea makes more sense if you have solar that you are giving away to the grid or want to be able to have backup for blackouts (which needs a lot more kit for islanding).
 

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And Over the next week, I'm monitoring time use of the high energy appliances (10kW electric shower, electric oven, Kettle, Dishwasher, Washing machine, Tumble dryer). I use approximately 35kWh per day as I do have four other adults living here.

The oven is used on the fringes and past 7 pm, as well as the ES solely in the morning. If it's clear that the appliances are not used between 4-7 pm, then I may as well go on the Octopus Agile tariff (Also have a ZS EV so can take advantage of charging).

Qs: Is it worth installing battery storage to further take advantage of the low (and even negative) rates overnight. Then, use the stored energy during that 4-7 pm period, always taking advantage of the lower night cost.

The reason why is because you can buy cheaper modular storage (+ inverter). Not sure about installation costs (are you allowed to install yourself or does it require a fully qualified electrician?).


I already understand that there'll be a limitation of battery discharge current, limiting me to 1.2kW per module. For a standard oven, it'll be around 2.4kW so need at least 2 to run the most likely device (I have gas-fired CH and hob).

So, am I missing anything? I'll check the results of the week and lets first see if the agile tariff makes sense...
Back of the fag packets maths, you could save an average of 6p based on 14p day rate versus 8p average on agile, you may be able to push this to 8 if you got really clever with 1/2 charging and discharging but would need a fair amount of effort to get that.

so 0.06 x 16kWh (with the PylonTech you can stack a maximum of 8 units per inverter), also not their is a maximum discharge of 3kWh even after 3 batteries (Thanks to Trevor L for confirming this). You could save around £1 a day, you could only really get one full charge and discharge over the day as to charge 16 will take around 8 hours.

8 batteries plus an inverter will cost you around 8k if you hunt around, 10 year warranty although that is based on it dropping to 70%. that gives you a best case saving of £3650 over 10 years versus the 8k cost of buying, not sensible really.

only way to make this would would be Solar and reducing your usage, even then in winter won’t change the facts.
 

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@dk6780 and @AnthonyL have it pretty right. I wouldn't say no to the idea, but go into it with your eyes open. A battery added to solar will have a typical payback of 10-15 years. A battery just operating on arbitrage (Economy 7, Go, Agile, etc.) will take more like 15-20 years.

Not sure about installation costs (are you allowed to install yourself or does it require a fully qualified electrician?).
It requires a suitably qualified person - some of the people on this forum could certainly do it themselves. It doesn't require a 'fully qualified electrician' (which implies 3 phase) but technically they need to be at least at the level of a 'domestic electrical installer', about the same level as an installer of charge points.

We sell the bits online here: Home Battery System Components - Tanjent Energy
We also do complete system installs, providing the kit etc., and then we charge around £300+VAT to do the installation.
 

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Isn't it great when you have such an honest vendor? @Trevor Larkum has given you some more details on the install to go with @AnthonyL better maths and we all reach a similar answer of it is not justified on finance alone.
 

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Discussion Starter #7
Isn't it great when you have such an honest vendor? @Trevor Larkum has given you some more details on the install to go with @AnthonyL better maths and we all reach a similar answer of it is not justified on finance alone.
Thank you all for your input across the board, appreciate it. As I said it's just a thought as I monitor usage.

FYI: I've lived with different adults for 3-4 years now. I've never been able to drop below 30kWh. However, as they either night work or are students, the day is normally occupied throughout. Plus, we have a tendancy to run appliances overnight anyway. I think we should benefit from Agile (+ 100% renewable is a bonus 😀)

I'm still a bit confused amount of packs required. Is the 8 just required for power density, to allow discharge of 3+kW?

I am currently predicting around 3-4kWh at that most expensive time. All the rest (~31) is outside.

I always had a rule of thumb to be 1C charge and 3C discharge current max for lithium based cells. I guess the inverter would be the limiting factor in most cases if the set was large enough.
 

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With the Pylontech I believe it is the battery that limits it, if you want to go crazy I believe the Tesla powerwall can do around 5kWh output but I am not an expert in it ( I dismissed it on cost) you will never find a battery that can output enough for showers i would imagine.

if your main target is to save money then a battery is probably not worth it, combine it with solar and it slightly changes but that is a lot more variable and if you are happy to shift can save a lot more for example I can make 4-5 kWh on the solar and pull another 2.5kWh from the battery for the short blips.
 

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Agree with the responses above.
Battery storage is still a nice to have and the ROI numbers dont stack up well compared to just getting solar.
If people have the money to spare, are not looking to move (basically settled, although you can of course move a Battery solution) then its a good to do feeling rather than makes good short term financial sense.
We have had a solar system for just over 5 years now which has paid for itself and we recently added a Powerwall2 and a Zappi for a Tesla M3P when that finally arrives after lockdown and also switched to Octopus Agile from OFTM.
We more than halved our elecy import when we got Solar and since the Powerwall2 and Agile have halved our import and associated costs again.
One of the key reasons we went for a Powerwall2 is the backup gateway, so we wont be plagued by outages as living in a small village we see outages in the summer months on non windy days, more in latter years than when we moved here decades ago, when it was predominantly winter outages. Not that its often been for long, just annoying.

Having said the above some people are switching to Agile and avoiding the 4 till 7pm peak by using slow cookers and other means to manually time shift. Not many can do that but it is an option.
If you and the others can avoid the 4 till 7 slot 100% then it makes sense to switch and see how it pans out.
If all good then maybe adding a Pylontech solution, one battery at a time works for many as you can spread the cost over many months or years.
It is one of the advantages of the modular solution. I have seen a number of forum friends go down this route over the years.
You do need the space (footprint) to have the rack mount setup and that does need to be indoors.
The Powerwall2 has a slender footprint and can be in or outdoors, but comes at a higher initially outlay.

Be interesting to hear what you decide to do.
 

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Discussion Starter #10
Having said the above some people are switching to Agile and avoiding the 4 till 7pm peak by using slow cookers and other means to manually time shift. Not many can do that but it is an option.
If you and the others can avoid the 4 till 7 slot 100% then it makes sense to switch and see how it pans out.
If all good then maybe adding a Pylontech solution, one battery at a time works for many as you can spread the cost over many months or years.
It is one of the advantages of the modular solution. I have seen a number of forum friends go down this route over the years.
You do need the space (footprint) to have the rack mount setup and that does need to be indoors.
The Powerwall2 has a slender footprint and can be in or outdoors, but comes at a higher initially outlay.
Agree with the responses above.
Battery storage is still a nice to have and the ROI numbers dont stack up well compared to just getting solar.
If people have the money to spare, are not looking to move (basically settled, although you can of course move a Battery solution) then its a good to do feeling rather than makes good short term financial sense.
We have had a solar system for just over 5 years now which has paid for itself and we recently added a Powerwall2 and a Zappi for a Tesla M3P when that finally arrives after lockdown and also switched to Octopus Agile from OFTM.
We more than halved our elecy import when we got Solar and since the Powerwall2 and Agile have halved our import and associated costs again.
One of the key reasons we went for a Powerwall2 is the backup gateway, so we wont be plagued by outages as living in a small village we see outages in the summer months on non windy days, more in latter years than when we moved here decades ago, when it was predominantly winter outages. Not that its often been for long, just annoying.

Having said the above some people are switching to Agile and avoiding the 4 till 7pm peak by using slow cookers and other means to manually time shift. Not many can do that but it is an option.
If you and the others can avoid the 4 till 7 slot 100% then it makes sense to switch and see how it pans out.
If all good then maybe adding a Pylontech solution, one battery at a time works for many as you can spread the cost over many months or years.
It is one of the advantages of the modular solution. I have seen a number of forum friends go down this route over the years.
You do need the space (footprint) to have the rack mount setup and that does need to be indoors.
The Powerwall2 has a slender footprint and can be in or outdoors, but comes at a higher initially outlay.

Be interesting to hear what you decide to do.
My current plan is to at least own the house 10-15 years, whether I live there and/or I am renting to other students in a similar arrangement I am now (long story short - I'm a final year student). That's the main reason why I cannot expect to electricity usage all together (I and others are lazy!), can nudge myself and others to swap washing/ drying clothes, dishwasher overnight.

I think everyone is right in saying just battery storage is not the answer to an ultimately financial question. Of course, I would like to be more environmentally conscious (Although, just by going to Agile, I will be 100% renewable). I have considered PV, but was quoted a ridiculous £4k for a 2.1kWp system (no storage) and didn't properly look elsewhere.

WRT Agile, from the data, the most expensive element, 10kW Electric Shower, is never switched on 4-7 pm (well, now 6 of us during isolation) which was my main concern. The oven uses an average of 1.2 kW as preheats/maintains 200C so I can justify using it for the period. The hob is gas.

I'm going to keep going with the data collection and just confirm the preliminary findings. I would guess it's worthwhile: preliminary findings at approx. £250 per year saving on electricity, and probably £50 a year on gas (I'm getting royally ripped off with a 35p SC and 3p per unit!).

One observation is that it seems that the Agile average is decreasing slightly over time, so the Feb19-20 data may be actually higher than present. I would guess the additional renewables coming online is helping.
 

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One observation is that it seems that the Agile average is decreasing slightly over time, so the Feb19-20 data may be actually higher than present. I would guess the additional renewables coming online is helping.
Suspect that the current Agile prices - lower overall and very low during the afternoon in particular - are more to do with load shifting and lower overall demand during lockdown. Likely to revert to previous pattern whenever things return to something approaching normal.
 

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Discussion Starter #12
Suspect that the current Agile prices - lower overall and very low during the afternoon in particular - are more to do with load shifting and lower overall demand during lockdown. Likely to revert to previous pattern whenever things return to something approaching normal.
Yes, that is true, people staying at home is also flattening the electricity demand curve too.

Either way, I think I'm looking at a very good saving using the 19-20 data (pre-COVID-19 catastrophe). Octopus is rated too for customer service. My previous suppliers either had money problems and/or poor customer service (IRESA,Eversmart, now Simplicity).

Time will tell and if it goes wrong I guess I'll just find another supplier. Octopus has no exit fee after all.
 

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Suspect that the current Agile prices - lower overall and very low during the afternoon in particular - are more to do with load shifting and lower overall demand during lockdown. Likely to revert to previous pattern whenever things return to something approaching normal.
Yes that is certainly having a large impact, but the general trend is downward, so expect that to continue after lockdown.
see Home - Energy Stats UK
heres one area example...
129742
 
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