Cheapest home storage battery options?

michaels

mickyduck55 said:

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."

How does it know how much charge your car needs to be full?

Verdigris

Either direct from the car or from the smart charger.

Petriix

Intelligent Octopus really wouldn't work for me. I leave the EV plugged in all day to trickle charge when there's surplus solar on the Zappi.

mickyduck55

Petriix said:

Intelligent Octopus really wouldn't work for me. I leave the EV plugged in all day to trickle charge when there's surplus solar on the Zappi.

What happens over winter when there is no surplus? Surely it would work for you then?

Petriix

mickyduck55 said:

Petriix said:

Intelligent Octopus really wouldn't work for me. I leave the EV plugged in all day to trickle charge when there's surplus solar on the Zappi.

What happens over winter when there is no surplus? Surely it would work for you then?

The short answer is "it's complicated". It's not that there's 'no surplus' in winter, but definitely long periods with next to none. Last winter 12.6p per kWh was not too hard to swallow, especially as lockdown meant we didn't drive especially far.

This year, if Neon Reef survive then it's 17.5p, otherwise 21p on the capped price. A home battery could supplement the minimal surplus to limit grid imports but it would still be more efficient (to a point) to charge the car when it's sunny.

The exact calculation depends on the unit price and round trip losses, with a but of a gamble looking at the forecast. I rarely need to charge the car to full so can be quite flexible.

As things stand, the Zappi is not on their list so it's a moot point for now. It might be a good option in the future if it doesn't interrupt the way I chose to charge. I'm just not certain about handing over the control of the charging as it could then become a battle to get it to do what I want.

Petriix

Has anyone looked at these Voltacon batteries? £1270 for 5.12kWh seems cheaper than anything else I've seen.

https://voltaconsolar.com/lithium-battery-100ah-5120wh-48v.html

Verdigris

That appears to be a game-changer, re home storage.

QrizB

100Ah at 48V for £1270 is definitely a step in the right direction!

Petriix

Ok, so what's the cheapest AC coupled inverter which will connect to the Voltacon batteries and offer overnight grid charging on Octopus Go?

Apparently it doesn't work with the popular Sofar ME3000SP. The Solis looks good at a little over £600. Is there anything else that I should consider? 

Verdigris

I think you'll find all battery storage comes from overseas. Our politicians are world leaders in making hot air but. as yet, we have no significant battery production.