Best EV tariff + SEG export tariff when you have solar & battery? How do people compare properly?

digitaldai

I’m trying to work out the best way to compare EV tariffs together with SEG export tariffs, for households that have solar + battery + EV.

Most comparison sites (and even MSE guides) seem to look at:
    •    cheap overnight EV rates or
    •    best SEG export rates
but not the combined effect when you have both.

For example, if:
    •    an EV tariff gives ~6–7p/kWh overnight, and
    •    a SEG tariff pays 15–20p/kWh for export,
then exporting solar and charging the car overnight can be financially better than using solar directly.

This means the key comparison isn’t just “cheapest EV rate” or “highest SEG”, but something like:
SEG export rate minus EV off-peak rate (i.e. arbitrage value), plus standing charges and peak rates.

My questions:
    •    Is there an existing tool or spreadsheet people use to compare EV + SEG properly?
    •    Are there any suppliers that consistently work well for solar + battery + EV households?
    •    Has anyone found a reliable way to model annual £ cost including export income?

At the moment it feels like you have to manually trawl tariff PDFs to do this properly, which seems mad given how common EVs and solar now are.

Interested to hear how others approach this, especially anyone who’s switched recently.

QrizB

It's a complicated question since the result depends on your own personal use, both for EV and for rest of house, and how much you generate, and on what make/model of car, charger and battery you have.

It also varies from season to season; the best winter tariff might not be te best summer tariff.

This does get discussed periodically here, and on the Green & Ethical subforum.

One quite common combination that is chosen is Octopus Go (or a similar EV tariff) in the winter, the Octopus Flux (or Intelligent Flux if you have a compatible battery) in the summer.

Depending on your specific use case, this might work for you, or it might not.

Netexporter

The Tim & Kat's Green Walk  Youtube channel has en excellent tool for complex tariff comparison.

digitaldai

I have had Eon next drive  6.5p 12-7am  and next Export 16.5p for last few years worked really well. I think it is ending now though.

QrizB

digitaldai said:

I have had Eon next drive  6.5p 12-7am  and next Export 16.5p for last few years worked really well. I think it is ending now though.

Yes, we had a recent thread from someone complaining that Next Drive was getting more expensive and EON would only pay 6p/kWh for export if you were on it.

There are other EV tariffs, none quite as cheap as Next Drive was but some are potentially cheaper than it's going to become.

Edit to add: here is the other thread.

https://forums.moneysavingexpert.com/discussion/6650642/eon-renewal-60-increase-and-no-justification

born_again

Have a look at MrEV on u-tube.

he has solar, batteries & runs EV. Has done a video on his costs not so long ago.

MWT

So much depends on your individual circumstances and your tolerance for capital expenditure.

If you keep trying to work out the optimum solution based on variable tariffs one one hand and longer term capital projects like batteries, solar PV etc. you will end up tied in knots.

We have taken the view that we cannot control or rely upon the tariffs that will be available from time to time so we just focused on maximising our flexibility in how we respond to the changes as they inevitably happen.

For us that translated into solar PV (4kWp), a large battery (Tesla PW2 x 2)  and 2 x EV together with EVSE that had a good public API (Zappi).

We fully acknowledge that is not a solution for everyone, but it works for us.

Net result is that whichever tariff offers around 4+ hours at a low rate, allows us to have 99%+ of our consumption at that low rate.

Currently that is Octopus IOG, it has been others in the past and will doubtless be others in the future.

digitaldai

My setup with E.ON Next Drive + Export has actually been very hard to beat.

Over winter I’ve been able to charge my home batteries overnight at 6.5p/kWh, which then comfortably last the whole day. Any excess solar gets exported at 16.5p/kWh, so the economics have worked really well.

The car is charged overnight most of the time anyway, as I’m often away at work during the week. As a result, I’ve almost never had to use daytime electricity, which is why I’m reluctant to move E.ON’s setup has been genuinely excellent.

I’m sure there’s a sweet spot elsewhere, but moving away may mean being much more hands-on with battery management, for example:

• deliberately charging batteries overnight if the solar forecast looks poor

• or setting up a Home Assistant automation to check the next day’s forecast and decide whether to grid-charge batteries overnight

Interested to hear from anyone who’s managed to replicate (or improve on) this kind of setup with another supplier, especially combinations of EV tariff + SEG that still stack up.

QrizB

digitaldai said:

My setup with E.ON Next Drive + Export has actually been very hard to beat.

But they're making it quite a lot worse.

digitaldai said:

Interested to hear from anyone who’s managed to replicate (or improve on) this kind of setup with another supplier, especially combinations of EV tariff + SEG that still stack up.

"New" E.ON Next Drive + SEG is beaten by Intelligent Octopus Go (7p/29p import) + Outgoing Octopus Fixed (15p export).

Reed_Richards

QrizB said:

....."New" E.ON Next Drive + SEG is beaten by Intelligent Octopus Go (7p/29p import) + Outgoing Octopus Fixed (15p export).

Except you might have to invest in a different charger or a different EV to make use of Intelligent Octopus Go.  How does regular Octopus Go compare?  

digitaldai

Reed_Richards said:

QrizB said:

....."New" E.ON Next Drive + SEG is beaten by Intelligent Octopus Go (7p/29p import) + Outgoing Octopus Fixed (15p export).

Except you might have to invest in a different charger or a different EV to make use of Intelligent Octopus Go.  How does regular Octopus Go compare?  

thanks,  I am thinking that looks best too, Intelligent Octopus Go + Octopus Fixed.  

Can you charge home batteries with intelligent octopus go on the cheap rate as well, aka the same time each night?

zappi charger..