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My query would be under what circumstances could you end up with a zero leccy bill ,not counting standing charge. Using TOU tariff with export of 90% of PV.

EG a 10kwp PV producing 10,000kwh/yr would generate £1350 from export. This would allow one to use say 4,000kwh at 25p/ kwh and 5,000kwh at 7p/kwh, 1000kwh from PV at 0p

In the UK household,
Avg leccy use is 2700kwh
Avg gas use 11,500kwh which with a HP at COP 3 is 3800kwh leccy
Avg EV 8K miles/yr ie 2000kwh
Total 8500kwh/yr

I wonder what size of batt being fully charged every night on the 7p TOU tariff you need to make this happen ? 8kwh perhaps.

I do not have the data to calculate further.

Easy peasy! You seem to have missed using a house battery to avoid peak consumption entirely and maybe even to deliberately discharge into the grid!

10kWp generating 10MWh in a year. Imagine you self-consume 25% of it and export 75% at 15p/kWh. That makes you £1,125.

So 2,500kWh off your 8,500kWh makes 6,000kWh at 7p/kWh is £420.

So you’re £705 in profit!

However you’ve failed to account for the poor real-world efficiency of your gas boiler. You should multiply your current gas consumption by 0.8 before applying the CoP. So you’d do much better than I’ve calculated above!

Nowty Towers real life example, OK, I've got a large battery, but my energy bill is currently very negative this year.



So far this year I have imported 11.628 MWh of leccy at a total cost (including standing charges and gas) of £1086.
My gas use is less than 1kWh per day (kitchen gas hob).

So far this year I have exported 11.139 MWh at an income of £1670.

Profit so far this year is £584, this will drop slightly by the end of the year but will be easily over £500.

And there is more,
Other free leccy rewards (mainly power hours) add up to another £20 of profit.
Saving sessions (not likely to be repeated) add up to another £370 of profit.

I reckon I could break even with a battery size of about 30 kWh, the problem is you need to have a large enough battery to run the house during all peak periods in winter. I could probably break even with an even smaller battery, say 20kWh but I would have to use some gas on the coldest days in winter for heating.

NOTE - I am not including any Ripple project or FIT income, thats extra income on top.

There is no easy way to calculate battery size, it depends on so many factors. Eg some people use very little electric all week and then use loads to cook a roast on Sunday. If you want to cover Sunday in this scenario then you need a much bigger battery than you would if your usage was more consistent. Additionally how much usage can be timeshifted is highly variable. Are you willing to run the washer/dishwasher in the cheap period? Then we have your willingness/ability to game additional cheapslots on IOG…

Although I'm rather new to the export game I can see the potential. I've been.paying £1 per month d/d for about 18 months. April 2022 was the last time i paid a direct debit of any significance. I paid a tenner a month for a year before dropping to £1

Export next year will.cover the whole year and as Nowty says. Ripple is just extra.

That £1 per month d/d covers EV too. Any wild charging I do comes off of Electroverse which is tied to my Octopus account. Mildly surreal tbh but true.

If I was asked I'd say what's needed to be bill free is a big PV array on roof, as many groundmounts or shed mounts as ye can.plus at least a 25kWh battery stack preferably 50kWh and export the hell out of it.

I have about 14kWh battery and I can just about make it work in winter, but its true that batteries lower running costs, and solar PV is the profit driving energy. The rest is a function of how much power you use. The less you use, the smaller the battery you can get away with but every bit of solar PV you can add gives a linear return in profit.

Am I right in thinking that you need to have an EV too in order to get the best TOUs?

Without the TOU it is much harder to achieve

The best tou tarrifs I’m aware of are Intelligent Octopus Go and Eon next drive V3. IOG requires an EV car test charge every now and then, but the eon one doesn’t need an EV. Octopus Go says it’s an EV tariff, afaik they don’t check; I think they’re just worried about miss-selling a tou tariff, hence ev badging it.

robl wrote: ↑Sun Nov 03, 2024 10:53 pm The best tou tarrifs I’m aware of are Intelligent Octopus Go and Eon next drive V3. IOG requires an EV car test charge every now and then, but the eon one doesn’t need an EV. Octopus Go says it’s an EV tariff, afaik they don’t check; I think they’re just worried about miss-selling a tou tariff, hence ev badging it.

Tomato have a 5p/kWh cheap rate but you give up 15p/kWh export…

cojmh wrote: ↑Sun Nov 03, 2024 9:24 pm Am I right in thinking that you need to have an EV too in order to get the best TOUs?

Without the TOU it is much harder to achieve

“Need to have an EV” is open to interpretation.

Vanilla Go (5hrs of 9p/kWh) you just tick a box to say you have one. I know people on IOG who borrowed an EV for the setup process, but they moved to a house that already had a charging point, probably not worthwhile installing one just for the tarif.