Electricity tarriffs with solar panels, batteries and EV

supasava

I have what is effectively a plug-in hybrid car (with an old type 1 charger). We had solar panels installed this summer. A Tesla Powerwall has gone in today and will be wired in shortly. So, we're at a point where we want to identify the best electricity tarriff (or combination of tarriffs for import and export) to go for. It looks far from obvious, and I've failed to find a flowchart or similar to work out what's best.

On clear, sunny days, over the course of a day we will generate using the solar more than we consume. Maximum generation for a day will be about the total of a full charge of the car from empty, a full charge of the Powerwall from empty, and the household consumption for the day.
On gloomy days, we will import pretty much everything we use (solar panels are surprisingly ineffective when it's overcast - I was expecting some generation, even if not much).
The car will normally want to be charged during the day, so not taking advantage of tarriffs that only allow car charging overnight.
We use LPG for central heating and hot water.
Over the course of a year, I suspect we will be net importers from the grid, but not hugely so.
We'd like to retain some charge in the Powerwall in case of grid outage, although we might add a backup generator in future to manage this for longer outages.
We have a 2nd gen smart meter providing half hourly data.
We are currently with So Energy, but not wedded to them (other than sorting out smart meter issues and estimating meter readings without explanation, we've been pleased with them).

Any thoughts please on how to go about identifying the most suitable tarriff or combination of tarriffs?

[Deleted User]

How long have you got? 

Have a look at Octopus Go at 12p/kWh offpeak (4 hours) and Octopus Intelligent (not all EVs or EVSEs): SEG at 4.1p/kWh.

Alternatively, Octopus E7 with fixed SEG at 15p/kWh or Agile Outgoing (variable SEG) OR The Tesla Energy Plan.

https://www.energy-stats.uk/

You cannot get the highest SEG rates on an EV tariff or the Tesla Energy Plan. The biggest limitation of the PW2 is that the owner cannot force Grid export when Agile Outgoing prices are high.

supasava

[Deleted User] said:

Alternatively, Octopus E7 with fixed SEG at 15p/kWh

Economy 7 sounds like it might be suitable for us. Topping up the Powerwall from the grid overnight, and doing all the usual household stuff during daylight to use any solar being generated (and using the charge in the battery is required), with excess solar going to battery or, if full, be exported. No idea how to set that up yet, but will look into it.

Many thanks

[Deleted User]

No problem. I am Go Faster (now withdrawn) at the moment but I will probably go for Flexible and Agile Outgoing in March. 

FWiW, over the past few months, Tesla has made big changes to its Time-Based Control algorithm. for example, last night, there was no PW2 Grid charge and the PW2 is now charging at 2.1kW. The new algorithm is based on forecast solar: the previous one looked back 2 days. 

supasava

[Deleted User] said:

I will probably go for Flexible and Agile Outgoing in March. 

That looks like a reasonable option for us too, other than the occasional overcast day when I need to charge the car during the day to do a second journey. I did wonder about Economy 10, as that used to have an off-peak period during the day that could be used to at least partially charge a car, but I'm not sure it exists anymore