Smart electric tariff

[Marvin]

On 05/07/2025 at 09:26, ReedRichards said:

Would it be such a sacrifice to trade-in your existing car for an EV?  I'm on the EON NextDrive tariff and it meshes very well with my other electrical items, ASHP, solar PV with battery. 

Hi @ReedRichards

 

Yes we have similar. We don't do many miles but we must have spent a total of about £100 over the last 2 years buying electricity for the EV. We use the 13amp charger and leave the vehicle plugged in when home and it only charges when the PV produces over 3.5kW. Of course this wouldn't work if the car was parked at work all day...

 

 

[joth]

3 hours ago, sharpener said:

 

I have a similarly complex charging regime but have been considering just charging battery to 100% every cheap period. The thinking is that every unit bought off the grid at 12.65p liberates a unit of PV which can be exported for 15p. Is there a flaw in this?

 

 

This is exactly what I've been doing for a couple years. I hear the argument that charging it to full every day is worse for longevity, but if I get drawn into that argument the only winner is never charging the battery at all.

I'm buying at 7p overnight and selling PV at 15p so even stronger argument. I do still redirect some PV to ashp (setpoint boost) and the battery. Financially I shouldn't do any those but they're more a nod to sustainability (and improving my home assistant self-sufficiency score) really

 

 

 

[JohnMo]

10 minutes ago, joth said:

ashp (setpoint boost)

I do that as well, found in the shoulder months on a sunny day, all the heating was done via PV at a warmer day temperature. It would be zero at night and heat pump stayed off. Not sure how you square that with potential export. If I get export accepted, I will import at 12.65p, and export at 15p. So it may be more beneficial to run ASHP in the day, better CoP and no defrosting.

[MikeSharp01]

28 minutes ago, JohnMo said:

I will import at 12.65p,

Where do you get a tariff like that we are on 25.97p import!

[JohnMo]

8 hours ago, MikeSharp01 said:

Where do you get a tariff like that we are on 25.97p import!

Octopus Cosy, 3x periods at 12.65p, 1 at about 33p and the rest at normal rate

[Thorfun]

22 hours ago, joth said:

For me I'd pay the £250 regardless anyway as it feels rewarding to be getting something back for the export but I know others that don't care. 

Getting paid for export on Octopus also means you don’t have to care what the forecast is for the day as you get paid more for export than on the cheap rate. So we just charge the batteries every cheap period on Cosy and if we export during that time then we’re still getting paid. 

[Thorfun]

13 hours ago, sharpener said:

 

I have a similarly complex charging regime but have been considering just charging battery to 100% every cheap period. The thinking is that every unit bought off the grid at 12.65p liberates a unit of PV which can be exported for 15p. Is there a flaw in this?

 

 

Exactly what we do. I also tried to find a flaw in it but couldn’t but my maths is not great! 😂

[Dave Jones]

On 30/06/2025 at 19:26, JohnMo said:

Currently have no smart meter that works due to a poor signal, after talking with a smart meter installer I now know how to get a working meter. Will explain for any one in a similar position.

 

Electric supplier has to have 3 unsuccessful smart meter installs. You then request the case is raised with the DCC. 6 weeks later they allow a 4G meter to be installed. Problem fixed.

 

So to my dilemma 

Have ASHP, GivEnergy 13kWh battery, PV but don't get paid for export. What is the best tariff to be on

 

Standard tariff make no sense with a battery.

E7 currently on that, easy to manage, but may not be most cost effective?

Cosy, seems easy to manage?

Agile, GivEnergy has controls built in, but expects export from what I can tell.

 

Any suggestions or users doing anything different?

Should I just pay octopus the £250 to allow export and be paid?

 

could you not get the octopus smart meter wifi bridge ?

 

We have one as mobile signal is non existent. Works great.

[JohnMo]

On 12/07/2025 at 08:50, JohnMo said:

Firstly now have a 4G smart meter, commissioning time was about 10 mins.

 

11 minutes ago, Dave Jones said:

could you not get the octopus smart meter wifi bridge ?

 

You must have missed above. We now have a 4G smart meter, all working. Now on Octopus Cosy. We are have an octopus mini instead of home display.

[JohnMo]

On 12/07/2025 at 08:50, JohnMo said:

schedule times. First cheap slot is setup as a smart schedule so it charges based on forecast generation of PV,

 

second slot set to 90% SoC fixed target. 90% 

 

Final charge is set for a fixed 100% SoC

Well that wasn't very effective.

 

First charge was ok, second charge and third charge didn't work well. At this time of year even with cooling running, I just don't need that much charge in the battery.

 

Second charge was changed to a smart charge, based on solar prediction, so it now charges to a minimum of 70%.  If first charge period was ok battery is past that point anyway from PV. Also during that cheap slot system set to consume from battery if battery charge is above 75%, not from the default which is from grid.

 

Third charge at 100%, meant I still had 80% charge remaining at time of first charge the next day and no room to accommodate much PV. So I exported - not being paid at this point. So that was changed to charge to at least 50% based on predicted PV generation and to self consume from battery if SoC is above 75%.

 

Hope the changes give a good balance between, import cost, limited or no export and battery not running out, if predicted PV is out.

[S2D2]

If you're not getting paid for export you'll probably have to reign back charges heavily at this time of year (depending on generation and usage of course). I only use the Cosy three charges during the winter, perhaps try just a single overnight charge?

 

I use three different prediction APIs and take the mean, it still needs a healthy buffer for day to day variance and forecasts change throughout the day. So it can't really be relied on without some ability to course correct, like forced export or spare battery capacity.

[Dave Jones]

On 01/07/2025 at 13:49, JohnMo said:

Unfortunately I don't have an EV, go and drive type tariffs won't work, unless they don't really ask you to prove EV.

 

I am thinking Cosy maybe a good choice, easy to programme times for charging etc. But an EV tariff is way cheaper 

 

octopus didnt ask me to prove i have an EV just that we had a car charger they could talk to, which we have as every new build has to have one. 

[Dave Jones]

On 13/07/2025 at 08:16, JohnMo said:

Octopus Cosy, 3x periods at 12.65p, 1 at about 33p and the rest at normal rate

 

7p from 11:30pm to 5:30am

 

only time our heat pump is on during the winter,  the eddi fires up the immersion as well taking the tank to 80c so heat pump isnt wasting time on DHW.

[JohnMo]

I use heat pump all year, if it's not heating it's cooling.

 

Yesterday I paid £1.17 including standing charge, so 67p for all electric. Can live with that.

[Dave Jones]

point being summer heat pump use is free anyway with excess solar. so its only winter where planning/arbitrage is needed.

[sharpener]

35 minutes ago, Dave Jones said:

point being summer heat pump use is free anyway with excess solar. so its only winter where planning/arbitrage is needed.

 

Not if you are also on Octopus Outgoing at 15p/unit. Then the marginal cost of anything and everything is 12.65 (if in a Cosy cheap period at night) or 15p otherwise as any consumption means you are foregoing the same amount of export. 

 

[JohnMo]

Now have export approved, took a while, but got there in the end.

 

Staying on Cosy, difference between import and export payments is marginally with inverter losses. Just had a look at what actually slipped into export and when into diverter to immersion and it sitting at close to 100kWh, and August weather hasn't been that good for solar.

 

So now to figure out

Do I charge battery to 100% every cheap period and just let everything export. Fit and forget, same strategy summer/winter leave battery software to look after everything.

 

Continue to self consume most and let some slip into the grid. Certainly don't need to charge based on forecast, so a nominal fixed %. But likely need to faff about between seasons setting different use patterns etc. Writing sounds like a faff.

 

Or something in between?

[S2D2]

5 minutes ago, JohnMo said:

Now have export approved, took a while, but got there in the end.

 

Staying on Cosy, difference between import and export payments is marginally with inverter losses. Just had a look at what actually slipped into export and when into diverter to immersion and it sitting at close to 100kWh, and August weather hasn't been that good for solar.

 

So now to figure out

Do I charge battery to 100% every cheap period and just let everything export. Fit and forget, same strategy summer/winter leave battery software to look after everything.

 

Continue to self consume most and let some slip into the grid. Certainly don't need to charge based on forecast, so a nominal fixed %. But likely need to faff about between seasons setting different use patterns etc. Writing sounds like a faff.

 

Or something in between?

If you never generate more than your export limit, just charge to 100% and forget about it. Things are more complex if you do.

 

You can still leave all the self use stuff in place which will reduce your overall import but not the price you pay.

 

Immersion diverter doesn't make sense with a heat pump on cheap rate though, I'd be turning that off.

[JamesPa]

On 12/07/2025 at 19:31, sharpener said:

 

I have a similarly complex charging regime but have been considering just charging battery to 100% every cheap period. The thinking is that every unit bought off the grid at 12.65p liberates a unit of PV which can be exported for 15p. Is there a flaw in this?

 

 

Nothing wrong in the logic.  I pay 7p nighttime, 25p daytime, 16.5p export.  The logic becomes beautifully simple, import as much leccy at night as you can (obviously assuming you can use it) even if it reduces self consumption of PV.

 

I love the simplicity, it probably won't last forever, but while this sort of tariff is offered it works well for me.

Edited 3 hours ago by JamesPa

[Kelvin]

I just applied for outgoing so a few weeks away before I can start getting paid. At the moment I’ve mostly been self-consuming since 14 July when it was installed. It’s generated 1.01MWh and of that 227kWh has been exported. I could have reduced that a bit by having the EV connected all the time to consume some of the excess. 
 

I did put the system into AI mode for a while to see what it did. Starting from 100% SoC it exported the majority of the solar production. Then a few hours out from the cheap tariff period (Intelligent Octopus Go) it discharged whatever was left in the battery to the grid and charged it back up during the cheap period and the house load was grid supplied. It varied the times it did all of this depending on SoC of the battery and it seemed to learn our consumption pattern. One of the problems I see with this is it will cycle the battery much more so not sure I’ll use it. 
 

 

Edited 3 hours ago by Kelvin