Economics of charging at 7p and exporting at 15p

[Stinsy]

"miserly 6.31% ROI"

I think there are a fair amount of people who would bite your arm off for an investment plan that returned 6.3% tax free every year - but I get your point it's a lot of capital investment and those returns are not guaranteed (tariffs may go up, as well as go down, battery cycle life, equipment failure etc)

I guess you've not looked at the S&P500 recently? 50% up over the last year!

[dan_b]

Well yes, my stocks and shares ISA has done pretty well this year, but there are years where it's done risibly, or worse! But hey, you pays your money and you make your choice!

"miserly 6.31% ROI"

I think there are a fair amount of people who would bite your arm off for an investment plan that returned 6.3% tax free every year - but I get your point it's a lot of capital investment and those returns are not guaranteed (tariffs may go up, as well as go down, battery cycle life, equipment failure etc)

I guess you've not looked at the S&P500 recently? 50% up over the last year!

[Yuff]

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[Yuff]

Sure, charging on off-peak then offsetting peak prices is much more compelling, still not amazing though:

Let me know if you think I've added it up wrong...

I’m assuming your figures are 1 cycle a day?
If you take a mixture of the export income and peak rate savings and do 2 cycles a day then the figures become more compelling.
I’m either charging or exporting 24/7 and have the system set up to accommodate that albeit I need to manually do IOG schedules when needed.
But we have 4 EVs and over the past couple of weeks have done several long journey and a 50 mile commute twice a day ( not the norm as SWBMO is visiting her mother in st Mary’s hospital london)which is probably averaging out at 150 miles a day conservatively and the net daily cost has been approximately £3.
The only gas we use is for a gas fire.

I think you've nailed it!

My batteries were not purchased with the intention of charging on cheap electric and discharging to the grid for profit. They were purchased with the intention of self-consuming back when the rate for export was derisory and I couldn't even get a ToU tariff (no smartmeter). Now I primarily use them to avoid paying peak rates.

My small (12kWh) pack isn't big enough to get me from one cheap period to the next however a bit of solar and some generous provision of additional cheapslots on gloomy days gets me through. I only bothered doing the admin required to get paid for electric so that I could max out the saving-sessions. However I found this made summer much less stressful because I could charge the battery to 100% every day rather than 50 or 75%. This was more of an ambivlelence about exporting rather than trying to export as much as I can.

However now we have the possibility to deliberately charge on cheap rate to export that energy back to the grid. And I was wondering if it was worthwhile. Your post has made me think I was too quick to dismiss the miserly 6.31% ROI. Sure, if you were to buy the batteries with the intention of profiting in this way, it isn't worthwhile. But the point I was missing was that this is ADDITIONAL money on top of the self-consumption/ToU shifting! And an extra £20 a month when you've already got an efficient setup IS worthwhile...

I originally invested with the same intentions, however over time and the changing of tariffs my usage has evolved to how I plan my import/export. I have this insane stupidity to always try and maximise my savings for no apparent reason even when it is for minuscule savings ( I even try to maximise the range on our EVs when we had a free charger up the road and I’d drive around with the air con off )
It drives SWMBO crackers
I did think too many cycles might not be worthwhile but I then decided how long will it last you can charge cheaper than you can export and decided make hay whilst the sun is shining