Cheapest home storage battery options?

arty688

Here's some more man maths.

If you are retired and drawing down you pension you savings could be considered tax free so add 20%(plus what they gain in your investment)
If you are employed you could put the savings into you pension making them tax free and if you company does salary sacrifice then you save the NI too. 

EVandPV

EVandPV said:

14th September 2021 here so I'll report back when we get our next bill.
Although our online account still says 14.19p. 🤔
Also, the standing charge seems to have reduced from 25p to 19p so that'll help offset any increase in the daytime rate.

Just got our September bill through.
It's split from 3/9/2021 to 13/9/2021 and 14/9/2021 to 2/10/2021 but the rates are the same for both periods. 
No change to the daytime rate or the standing charge and presumably we're on this for at least another year.

michaels

So I'm thinking that Octopus agile actually reflects real electricity prices that other companies will eventually catch up to once the cap rolls forward.

So as an experiment we could look at octopus prices a month at a time over the last year and for each months average time of day rates work out what the total electricity bill would be for an 'typical' use profile - say 15kwh per day spread as 3kwh shifted to cheapest times, 2kwh at morning peak price, 4kwh at average day price and 6kwh at evening peak price.

Then we could try various different battery sizes and work out how much the bill could be reduced with storage shifting the highest price usage to the lowest import rate.  So for example end up with something like:
Feb 21 prices 10KWh storage saving is £20pm
Feb 21 prices 6kwh storage saving is £14pm
...
Sep 21 prices 10Kwh storage saving is £42pm

Of course we have no idea what prices will be going forward but we could see over the different scenarios what the payback time of a battery system might be.

mickyduck55

michaels said:

So I'm thinking that Octopus agile actually reflects real electricity prices that other companies will eventually catch up to once the cap rolls forward.

So as an experiment we could look at octopus prices a month at a time over the last year and for each months average time of day rates work out what the total electricity bill would be for an 'typical' use profile - say 15kwh per day spread as 3kwh shifted to cheapest times, 2kwh at morning peak price, 4kwh at average day price and 6kwh at evening peak price.

Then we could try various different battery sizes and work out how much the bill could be reduced with storage shifting the highest price usage to the lowest import rate.  So for example end up with something like:
Feb 21 prices 10KWh storage saving is £20pm
Feb 21 prices 6kwh storage saving is £14pm
...
Sep 21 prices 10Kwh storage saving is £42pm

Of course we have no idea what prices will be going forward but we could see over the different scenarios what the payback time of a battery system might be.

Octopus Go is much simpler than that.. (I think) I am your average user 10-15 kWh / day 

I have 10.5 kWh battery storage so between 8 and 9 kWh useable as I change the DOD depending on time of year as residual charge is higher in the sunnier months.

My Go period is 20:30 - 01:30 @5.5 p. so I can usually mange to get through to the cheap period so I rarely buy electricity at full rate, I use a Pi to decide how much charge I need during the Go period.

Back of fag packet calc Im saving about £400 a year so at todays prices ROI on my batteries is about 10.5 years at todays prices, I already had the solar.

The ROI was not really a factor for me I like the idea of the batteries and I am able to afford to reinvest my FIT due to my high rate

Im no mathematician so this maybe complete B***S**T  

michaels

mickyduck55 said:

michaels said:

So I'm thinking that Octopus agile actually reflects real electricity prices that other companies will eventually catch up to once the cap rolls forward.

So as an experiment we could look at octopus prices a month at a time over the last year and for each months average time of day rates work out what the total electricity bill would be for an 'typical' use profile - say 15kwh per day spread as 3kwh shifted to cheapest times, 2kwh at morning peak price, 4kwh at average day price and 6kwh at evening peak price.

Then we could try various different battery sizes and work out how much the bill could be reduced with storage shifting the highest price usage to the lowest import rate.  So for example end up with something like:
Feb 21 prices 10KWh storage saving is £20pm
Feb 21 prices 6kwh storage saving is £14pm
...
Sep 21 prices 10Kwh storage saving is £42pm

Of course we have no idea what prices will be going forward but we could see over the different scenarios what the payback time of a battery system might be.

Octopus Go is much simpler than that.. (I think) I am your average user 10-15 kWh / day 

I have 10.5 kWh battery storage so between 8 and 9 kWh useable as I change the DOD depending on time of year as residual charge is higher in the sunnier months.

My Go period is 20:30 - 01:30 @5.5 p. so I can usually mange to get through to the cheap period so I rarely buy electricity at full rate, I use a Pi to decide how much charge I need during the Go period.

Back of fag packet calc Im saving about £400 a year so at todays prices ROI on my batteries is about 10.5 years, I already had the solar.

The ROI was not really a factor for me I like the idea of the batteries and I am able to afford to reinvest my FIT due to my high rate

Im no mathematician so this maybe complete B***S**T  

That was the sort of back of an envelope I was thinking of - however I don't think the go tariff is available anymore (and I didn't realise you could get such an early cheap period either) so working out savings based on these prices may not be that realistic for a new installation.

Petriix

mickyduck55 said:

michaels said:

So I'm thinking that Octopus agile actually reflects real electricity prices that other companies will eventually catch up to once the cap rolls forward.

So as an experiment we could look at octopus prices a month at a time over the last year and for each months average time of day rates work out what the total electricity bill would be for an 'typical' use profile - say 15kwh per day spread as 3kwh shifted to cheapest times, 2kwh at morning peak price, 4kwh at average day price and 6kwh at evening peak price.

Then we could try various different battery sizes and work out how much the bill could be reduced with storage shifting the highest price usage to the lowest import rate.  So for example end up with something like:
Feb 21 prices 10KWh storage saving is £20pm
Feb 21 prices 6kwh storage saving is £14pm
...
Sep 21 prices 10Kwh storage saving is £42pm

Of course we have no idea what prices will be going forward but we could see over the different scenarios what the payback time of a battery system might be.

Octopus Go is much simpler than that.. (I think) I am your average user 10-15 kWh / day 

I have 10.5 kWh battery storage so between 8 and 9 kWh useable as I change the DOD depending on time of year as residual charge is higher in the sunnier months.

My Go period is 20:30 - 01:30 @5.5 p. so I can usually mange to get through to the cheap period so I rarely buy electricity at full rate, I use a Pi to decide how much charge I need during the Go period.

Back of fag packet calc Im saving about £400 a year so at todays prices ROI on my batteries is about 10.5 years at todays prices, I already had the solar.

The ROI was not really a factor for me I like the idea of the batteries and I am able to afford to reinvest my FIT due to my high rate

Im no mathematician so this maybe complete B***S**T  

I think the maths look slightly better with the EDF EV tariff at 4.5p per kWh. Assuming that you can avoid all peak demand, you'd be saving ~ 16p per kWh at today's prices. I'm importing around 3000kWh per year so that's £480 saved, but with the ability to store my surplus solar I'd cut my imports in half as well so that's 1500kWh at 4.5p which is another £67. If I can get close to 10kWh installed for around £4k then it's about 7.25 years ROI. The huge price hikes have really changed the numbers.

mickyduck55

michaels said:

mickyduck55 said:

michaels said:

So I'm thinking that Octopus agile actually reflects real electricity prices that other companies will eventually catch up to once the cap rolls forward.

So as an experiment we could look at octopus prices a month at a time over the last year and for each months average time of day rates work out what the total electricity bill would be for an 'typical' use profile - say 15kwh per day spread as 3kwh shifted to cheapest times, 2kwh at morning peak price, 4kwh at average day price and 6kwh at evening peak price.

Then we could try various different battery sizes and work out how much the bill could be reduced with storage shifting the highest price usage to the lowest import rate.  So for example end up with something like:
Feb 21 prices 10KWh storage saving is £20pm
Feb 21 prices 6kwh storage saving is £14pm
...
Sep 21 prices 10Kwh storage saving is £42pm

Of course we have no idea what prices will be going forward but we could see over the different scenarios what the payback time of a battery system might be.

Octopus Go is much simpler than that.. (I think) I am your average user 10-15 kWh / day 

I have 10.5 kWh battery storage so between 8 and 9 kWh useable as I change the DOD depending on time of year as residual charge is higher in the sunnier months.

My Go period is 20:30 - 01:30 @5.5 p. so I can usually mange to get through to the cheap period so I rarely buy electricity at full rate, I use a Pi to decide how much charge I need during the Go period.

Back of fag packet calc Im saving about £400 a year so at todays prices ROI on my batteries is about 10.5 years, I already had the solar.

The ROI was not really a factor for me I like the idea of the batteries and I am able to afford to reinvest my FIT due to my high rate

Im no mathematician so this maybe complete B***S**T  

That was the sort of back of an envelope I was thinking of - however I don't think the go tariff is available anymore (and I didn't realise you could get such an early cheap period either) so working out savings based on these prices may not be that realistic for a new installation.

Hi Sorry  I am actually on "Go Faster".. which gave me the option a few months ago to change my time period and have an extra hour for 0.5p a kWh more so I jumped at it.  It really does work for me especially the early evening cheap period.
I didnt know that "go" had been withdrawn.. I have just been offered "Intelligent Octopus" but I'm sticking where I am.

mickyduck55

Petriix said:

mickyduck55 said:

michaels said:

So I'm thinking that Octopus agile actually reflects real electricity prices that other companies will eventually catch up to once the cap rolls forward.

So as an experiment we could look at octopus prices a month at a time over the last year and for each months average time of day rates work out what the total electricity bill would be for an 'typical' use profile - say 15kwh per day spread as 3kwh shifted to cheapest times, 2kwh at morning peak price, 4kwh at average day price and 6kwh at evening peak price.

Then we could try various different battery sizes and work out how much the bill could be reduced with storage shifting the highest price usage to the lowest import rate.  So for example end up with something like:
Feb 21 prices 10KWh storage saving is £20pm
Feb 21 prices 6kwh storage saving is £14pm
...
Sep 21 prices 10Kwh storage saving is £42pm

Of course we have no idea what prices will be going forward but we could see over the different scenarios what the payback time of a battery system might be.

Octopus Go is much simpler than that.. (I think) I am your average user 10-15 kWh / day 

I have 10.5 kWh battery storage so between 8 and 9 kWh useable as I change the DOD depending on time of year as residual charge is higher in the sunnier months.

My Go period is 20:30 - 01:30 @5.5 p. so I can usually mange to get through to the cheap period so I rarely buy electricity at full rate, I use a Pi to decide how much charge I need during the Go period.

Back of fag packet calc Im saving about £400 a year so at todays prices ROI on my batteries is about 10.5 years at todays prices, I already had the solar.

The ROI was not really a factor for me I like the idea of the batteries and I am able to afford to reinvest my FIT due to my high rate

Im no mathematician so this maybe complete B***S**T  

I think the maths look slightly better with the EDF EV tariff at 4.5p per kWh. Assuming that you can avoid all peak demand, you'd be saving ~ 16p per kWh at today's prices. I'm importing around 3000kWh per year so that's £480 saved, but with the ability to store my surplus solar I'd cut my imports in half as well so that's 1500kWh at 4.5p which is another £67. If I can get close to 10kWh installed for around £4k then it's about 7.25 years ROI. The huge price hikes have really changed the numbers.

My 10.5 kWh was about 4.5 K installed

michaels

Ok, this is my example
15kwh of which 3kwh used before 4.30AM, 4kwh used between 4.30 and 15:30, 6kwh used between 16:00 and 19:30 and 2kwh used after 20:00

Compared with
16kwh of which 10kwh used before 4.30AM, 4kwh used between 4.30 and 15:30, 0kwh used between 16:00 and 19:30 and 2kwh used after 20:00
This is using 7kwh to charge a battery before 4.30 and 6kwh discharged from the battery between 16:00 and 19:30 (assumes 1kwh efficiency loss).

Based on Octopus Agile monthly average prices for these time periods between Feb 18 and Jun 21, the annual saving from the battery scenario is between £290 and £390 (average £330); since June though this has fallen as follows - £270, £235, £96 and...-£2!!!!

Not sure what a 7kwh battery system would cost and longevity but given current low interest rates any sort of payback period less than about 20 years sounds like a win.

I have chosen agile as this reflects actual electricity prices (until recently when the 35p cap cut in) which I think may be a more reasonable long term comparison than the super low 'ev' style tariffs that probably won't be around forever.

mickyduck55

michaels said:

Ok, this is my example
15kwh of which 3kwh used before 4.30AM, 4kwh used between 4.30 and 15:30, 6kwh used between 16:00 and 19:30 and 2kwh used after 20:00

Compared with
16kwh of which 10kwh used before 4.30AM, 4kwh used between 4.30 and 15:30, 0kwh used between 16:00 and 19:30 and 2kwh used after 20:00
This is using 7kwh to charge a battery before 4.30 and 6kwh discharged from the battery between 16:00 and 19:30 (assumes 1kwh efficiency loss).

Based on Octopus Agile monthly average prices for these time periods between Feb 18 and Jun 21, the annual saving from the battery scenario is between £290 and £390 (average £330); since June though this has fallen as follows - £270, £235, £96 and...-£2!!!!

Not sure what a 7kwh battery system would cost and longevity but given current low interest rates any sort of payback period less than about 20 years sounds like a win.

I have chosen agile as this reflects actual electricity prices (until recently when the 35p cap cut in) which I think may be a more reasonable long term comparison than the super low 'ev' style tariffs that probably won't be around forever.

Thanks for the calculations..

They probably wont be about forever but Octopus are just launching a new one

"We're getting ready to launch a groundbreaking next generation smart tariff: Intelligent Octopus. We're delighted to tell you that you've been chosen as part of a select group of customers to get early access, test it out and give us feedback. 

Why sign up: Intelligent Octopus gives you access to a whopping six hours of super-cheap electricity overnight (much longer than other smart tariffs) that you can use for electric vehicle charging and any other energy needs. What's more, we'll manage your charging to make sure that you only fill up on the very greenest electricity. In short, you'll get a chance to save cash, charge your electric vehicle in a greener way, and participate in the future of smart energy.

How it works: You'll get a six hour low-cost night rate at 5p/kWh between 11:30pm and 5:30am - two hours longer than our Octopus Go tariff. You simply register with the Intelligent Octopus app and tell us when you need your electric vehicle charged by. We make sure that the car's charged by that time. We'll schedule your car to charge at times when renewables are abundant, reducing the strain on the grid and the need to burn dirty fossil fuels."