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Octopus Tesla Energy Plan

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There is a view that the plan causes Powerwalls to cycle far more

My understanding is that cycling 100%-50%-100% twice is the same (in terms of longevity) as 100%-0%-100% once, so unless Tesla discharge it "fully", or equivalent, twice a day I'm not concerned. Presumably to do that they would need "peak demand" to occur twice a day.

Even with an evening peak-time export to grid, my own use won't cause much of a second discharge during the day. Currently I would charge from PV during the day, discharge in the evening and (in my case - high base-load :( ) top up during the night.

In Winter currently I would charge overnight and discharge (once) during the day. I suppose Tesla might re-charge during the day, if cheap energy available, in order to be able to also discharge again for the evening peak.

If I happen to need to charge my car during the day currently that would take some from PowerWall. Presumably Tesla would/could disable PowerWall if I put the car on charge during the day, which would be better

I must be missing something? because I'm not seeing a scenario for an increase in the average number of charges-per-day.
 
I have been on the TEP since July 2020. They have set my Powerwall reserve at 20%. In my experience the battery begins a discharge at 16:00 precisely and will run until it hits 20%. The Powerwall is then topped up in the middle of the night leaving some room for Solar PV generation to further fill it the following day. I have never experienced more than this one single daily battery cycle, which is no more use than I would make of it if I were not on the TEP and retained control.

We are a high electric use house. The TEP rate was initially 8p and no daily standing charge (7/2020 - 7/2021) and is currently 8.72p and a daily standing charge of 22p until July this summer. Not sure what the new rate will be but I am expecting it will remain a good deal or I will consider leaving the plan.
 
That's interesting, how did you measure that? It seems in keeping with Tesla's claimed "90% road-trip efficiency".

Although, I'm not sure the batteries will lose efficiency. Surely they lose capacity but shouldn't the efficiency stay the same?
Using the data download from the Tesla app I calculated total power in (i.e. delivered to house or PW) as Solar plus From grid less To grid and assumed that the difference between this and the Home use was power lost due to the PW.

As this was for a yearly calculation I did not take account of different PW SOC at the beginning and end, and I assumed that To grid is all excess solar leakage.
 
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That's interesting, how did you measure that? It seems in keeping with Tesla's claimed "90% road-trip efficiency".

Although, I'm not sure the batteries will lose efficiency. Surely they lose capacity but shouldn't the efficiency stay the same?

Careful. Powerwall battery usage/attachment isn't the same as car battery usage. For starters, the Powerwall has to present itself to the grid and your home as good old AC mains power, so there's more conversions going on (with each conversion taking a loss). Newer Gateways can (I think - I don't have one) take DC straight from solar to skip one step but the general path to use stored solar to power your car is, frankly, fairly ridiculous:

  • Generated as Solar(DC).
  • Converted to AC by Solar Inverter
  • Converted back to DC by Powerwall for storage
  • Converted to AC for supply to grid/home
  • Converted to DC by car charger for storage in car battery
  • Converted to AC for use by Induction motors on car.

Only the last 2 conversions have any relevance to Tesla's "90% road-trip efficiency"; it's the first 4 steps that apply to the 88% Powerwall efficiency reported above (and which I can generally echo based on my own calculations).
 
I'm currently trying to run the man math on this, but to me it doesn't really seem to add up.
as more and more people move to EV's the likelihood of someone having an EV that needs charging as well as their house increases, especially with a tesla product. So the likelihood is you need ALL your power and then more, unless you have a very large solar array or don't actually drive much
So here's where I'm at -
If Tesla control your power wall Octopus give you 12p... they charge you 12p (this is based on where I am, so regional differences and all)
If you control your powerwall (and ignore feed in as you need it all) Octopus Go charge you 7p off peak and 30 peak if you use it.
So lets say I have enough solar to run the house and charge my pack at least 50% during the day -
On Tesla energy plan I get my £1.25 when they discharge the battery to 20% but then it charges back to 50% which costs me 47p and I also then use 4kwh for the house (48p) and I charge my car in the evening say a modest 15kWh (£1.80). My total cost that day is £2.75 minus my £1.25 payout so £1.50
Flip that to using Octopus Go and doing the same, so run my power wall down to 20% in the evening then charge off peak to 50% and charge my car off peak, (minus the 4kw odd left in the power wall to drop it to 20%). This means I'm paying 27p to charge the power wall and 77p to charge my car, so £1.04

So with those math, in that scenario, octopus go is 30% cheaper...... OR am I getting it wrong about the powerwall recharge on the tesla energy plan and you don't pay to put energy back in that they take out?
 
I think you underestimate the impact of the better rate for exports to grid, ie12 p in your case. If you're on octopus go you can't be on octopus outgoing (which pays 7.5p), so I think you end up on their default export tariff, which is 4.1p if I am reading correctly.

Even with a powerwall to buffer things there's still a massive gap between a cloudy december day where you'll be lucky to get more than 1-2kWh and a sunny may/june day where you might get 40-50 kWh + (ie more than you can store in the PW, and if you're not at home, energy that can't go into your car either.

If you have a lot of consumption that you can't shift to the go period / sunny days (eg a heat pump) then the tesla energy plan is also great.
 
Another way to look at it this - you "use" 100% of the energy your solar panels produce on TEP.

Everything not immediately used is fed into TEP at 12p, you then draw it back later when needed at 12p - net zero.

So solar panels, PW, and TEP means you can "use" all your solar - you won't be feeding it back at 4p to later take it at 7.5p or 30p.

I think the best solution is actually GO from Oct-Feb and TEP from Mar-Sep !!
 
In 2021, on Octopus GO, we drew 3.77Mwh from the grid at a blended rate of about 8p per kWh and exported about 10% of the power generated by our solar panels, .58 Mwh at a rate of 0p per kWh, net cost about £300. If we were on the TEP, at 12p per kWh, the net cost, ignoring any extra losses due to higher PW usage, would be about £380. In our case, in addition, we would have to give up the guaranteed deemed FiT export payment of over £60. Of course, the big advantage of the TEP is that there is no need to micro manage usage versus generation or move power usage to the off-peak period.
 
Just getting to the end of my second quarter with TEP. It works well for us. We are net exporters, having 2 arrays - the first is 3.84 declared net capacity facing SE, the second is 4.8 declared net capacity facing SW. These were installed in first and second year of FITT, so they have already paid back. We have a single Powerwall. We do not have an electric car. We have our Generation Tariff with original supplier (SSE) and no longer receive the "deemed export" amount.

Quarter 1 was Dec 20th to Mar 19th 2022 - during this period, we imported 1,196 and exported 1,189 - a net of just 6 Kw - less than £1. During this period we generated 1,156.

65 days into Quarter 2, we have imported 361 and exported 1,790, a net export of 1,429 - worth £168. During this period we generated 2,145.

The 14th May is the single most profitable day so far, we generated 54.7KW with a net export of 45.5, worth £5.35.

We use gas for heating and hot water. The big question now for this year is whether we get more back for the electricity that we sell than we pay for the gas that we use. (ignoring the day charges). At the moment we are £147 in debt, but with a run if sunny days.....who knows. We have made an overall profit on every day since the start of April.

We are seeing the same behaviour as others, - Tesla charge up the battery if they "think" it is needed, they do seem to use the following days weather to decide what to do and also they start drawing from the battery in the late afternoon, leaving it at 19% each day.

Finally, the "waste". In the first quarter 157Kw went into the battery that did not come out again, about 20p per day. So far, in the second quarter, this is 97Kw, about 17.5p per day. I calculate the waste as "Generated" + "Imported" - "Used"- "Exported". Apart from anomalies on a few days, this is becoming a very consistent figure in each quarter - 1.7 in quarter 1 and 1.4 in quarter 2.

So far so good, I think. Will be interesting to see what happens to the rates when we reach the end of the current contract.
 
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The TEP seems to be the only reasonable tariff left for those of us who are only now getting smart meters installed. Octopus Go doesn't seem to be available anymore.

Our night rate is just shy of 20p and our standing charge is over 40p. The PW tells me that in 2021, for example, we took just under 5,000 kW from solar and our house needs were around 7,000 kW. We only exported about 150 kW over the whole year and this bagged us £240. In 2021 we paid £950 in total for our electricity and gas (don't have a separate figure for electric only) so our energy bills aren't huge anyway although they'll probably increase to around £1200 this year due to the price hikes. If Octopus Go isn't available, switching to the TEP seems to make sense just from a unit/standing charge cost as that would halve.

Would others who have more experience concur?
 
TEP is pretty good but you’re not really leveraging the battery - the supplier is. May be useful for you to get used to your battery/home usage in case you switch later though. And it does mean you get 100% utilisation of solar, where others may have excess generation after topping up the battery. That can make it swing much better than go/intelligent if you have a big enough array.

if you don’t have a smart meter to log your usage you may be estimating for now but even with a small array many people will generate more than they use over 24 hours. At that point you’re almost off-grid aside from the standing charge
 
We've had our PW since Dec 2019 so we're pretty familiar with it and the app tells us exactly how much power the house has drawn over that time. We're on a 5.2kW array and pretty much off grid from April until September. We usually have surplus solar from June onwards and particularly during the summer hols when we're away a lot. We only got onto our FIT in 2018 so only get 5p/kW export rates so not a lot to lose there.
 
We've had our PW since Dec 2019 so we're pretty familiar with it and the app tells us exactly how much power the house has drawn over that time. We're on a 5.2kW array and pretty much off grid from April until September. We usually have surplus solar from June onwards and particularly during the summer hols when we're away a lot. We only got onto our FIT in 2018 so only get 5p/kW export rates so not a lot to lose there.

have you done rough math for the year? eg kwh generated (x11p) - kwh consumed (x11p) ? 5.2kw is a decent size

edit: pvgis slapping you South facing around woking for example gives approx 5300kwh generated per year. thats 14.5kwh per day. If you use exactly that, then you’d be net neutral on cost (other than standing charge). 14.5kwh/day = 5300kwh per year. 11p for export, 11p for consumption cancels out

if you used 10kwh per day (bit more challenging), then that would also cover the standing charge so you’d be net £0 for electric
50p/day standing charge = £182 per year - equivalent to 1650kwh solar generation at 11p/kwh. so 5300kwh - 1650kwh ‘spent’ to pay for the standing charge leaves you with 3,655kwh for the year

sound about in line with your thoughts?
 
so, taking your helpful formula of generated - consumed, I end up with a negative figure of £253.

I used our PW's record of entire house consumption for 2021 (7132 kWh) and solar generated (4907 kWh). Last year, we drew 3225 kWh from the grid i.e. we used 3907 kWh of our solar to fund our house needs.

I may have this all wrong, but if that figure of £253 would be our cost for electricity and I add to that the TEP standing charge, that gives me a total cost of £326 which is under half of what we spent in 2021.

I'm pretty rubbish at maths and have only just now stumbled on the TEP so I could have this all wrong of course!