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A question about battery life

 
Energy Storage
Last Post by Gary 7 hours ago
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 AdamK
(@adamk)
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351 kWhs
Joined: 1 month ago
Posts: 47
Topic starter 02/04/2025 7:26 pm  

ive had solar PV for just over 10 years and havent considered batteries because of what would seem a very poor ROI as i have a gas boiler currently and get 15p pkwh export. but were going ASHP soon and with the winter time being when the HP is working hardest and the solar at it lowest output it would seem to make more sense.

ive just watched the latest QA, where again battery storage is mentioned as a way of leveraging cheap time of use tariffs, but the thing that dosent get mentioned is the wear on the battery if your near enough doing full cycles every day. does this scenario still add up? to my mind youve goto be saving several hundred pounds a year at least otherwise surely all your doing is using the money youve spent on the battery to effectively get it back in savings before having to buy another battery? bit like buying your electric at discounted price over 10 years say.

This topic was modified 4 hours ago by Mars

   
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 Gary
(@gary)
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2877 kWhs
Joined: 2 years ago
Posts: 329
03/04/2025 8:03 am  

I suppose it depends on what battery you get I can only comment on the powerwall I had my first for 5 years before the inverter went and it was at 95% of it original capacity and it had been cycled full to empty pretty most days. 

New one was replaced under warranty only had it 2 months but it started with 15kwh it has lost 0.5kwh and is now steady at 14.5kwh only 13.5kwh is usable so has plenty of head room before it even gets below 100%.

The PW circled below have been discharged every day and are still at 90% capacity. 

image

 

Whether the math stacks up for your situation is very personal.  I charge up every night in the winter use all the battery and a bit of peak electricity in the depths of winter, once it hits March/Apr then heat overnight at cheap rate and use battery during day, export all PV.   

My electricity bill for 2024 was just under zero and that is running a EV at 5000 miles a year and a fully electric house, no gas.

To get the best return to will need to ditch the deemed export portion of your FIT that pays 50% generation at ~8p and go to metered export so you get 100% you export at 15p with Octopus.

My Export last year was worth just over £1000 my import 95% at off peak was £950

This post was modified 7 hours ago by Gary
This post was modified 6 hours ago 2 times by Gary

   
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