Tariffs with solar and battery, this time of year hardly matters, but what about winter?

[ericmark]

Since hardly any import this time of year, at the moment it does not matter. But December 2024, only 5 days, did I export, best 10.3 kWh, but many days down to just over 1 kWh. I use around 12 kWh, so to move 5.76 kWh from off-peak to peak time would likely help? But I am now well aware that last year I messed up.

I have tried looking at my records, but only this tells me how many kWh bought at off-peak, and how many at peak. I can see total for the days, but little breakdown between peak and off-peak. Total £75.51, Standing charge £18.34, Peak £29.40, Off-peak £27.77 so as kWh Peak 94 kWh off-peak 310 kWh.

So with a single rate, standing charge goes up to £21.13, and so the total would have been £123.67 remember this is the worst month. £121.59 if I consider the export.

But for December last year, I would have been better off with the split tariff (31.31p/8.95p) but this time of year, better off with single tariff. Last year 15th October fitted a second battery, so records before that date are not much help. And now getting paid for export. But November £62.98 with off-peak and £104.77 without it, that includes payment for export.

So it would seem Sept to Feb better off with off-peak, and March to August better off without it. But before was not being paid for export, now I am, and some tariffs mean export payments likely reduced. Was with British Gas last year, now with Octopus, and there are so many tariffs it is mind-boggling. And so easy to jump from the frying pan into the fire.

So the question is, what have others done?

 

[StephenStephen]

Yes, there is a tradeoff between financial advantage and the amount of time playing with the system!
It's worth having a look at how often you can change the tariffs you're interested in using with Octopus.
Some people stick with Flux or Go, some people do change tariffs twice a year - Agile/Flux used to be a classic combination I think...
OctopusWatch has a compare function - I've not looked into that function specifically, but in general terms it's a great app.

 

[Munroast]

I'm hoping to write an app to link the agile prices to when the inverter charges the battery - if I could get it to work and this winters agile prices were simillar to last years then there is a lot of money to be saved. windy periods during the night and they would be paying me to charge my batteries!

 

[JohnW2]

So it would seem Sept to Feb better off with off-peak, and March to August better off without it.

Given some guestimates about solar generation at different times of year, it ought to be fairly trivial to calculate the relative costs of single-rate tariff and dual-rate (or more complex) tariff over a full 12-month period.

However, as I recently wrote in another thread ....

It all seems like a lot of effort to me - and, if it were me, I suspect I would probably decide that I had better things to do with what time I have left!

 

[ericmark]

Until I realised on a single rate tariff I was likely going to pay £20 a month more, I was not worried. So unless I change to a duel or more rate tariff in winter months, it will cost me an extra £100.

Ideal for me would be off-peak 11:30 pm to 1 am, that is enough time to charge the batteries, and also enough time between 1 am and solar being available to ensure a minimal amount will be feed back into the grid.

But the times are more like 2 am to 5 am, to have a reasonably cheap day rate (28.5p) but the off-peak is really not that cheap at 17.1p and should I run out 4 pm to 7 pm there is a massive 39.9p rate, that's the Octopus Flux. The Octopus EV rate seems too good to be true, I wonder what one needs to get it, maybe an EV, and it does not say what the export rate is. I tried to get answers from the website, and it seems some tariffs one has to give control to Octopus, so they tell your batteries when to charge and discharge.

And at time point

It all seems like a lot of effort to me - and, if it were me, I suspect I would probably decide that I had better things to do with what time I have left!

seems a very good point.

However, a lot of time between now and September, so time to find the answers.

 

[JohnW2]

..... seems a very good point. .... However, a lot of time between now and September, so time to find the answers.

I suppose I shouldn't really joke about it ()although 'what else can I do?' !), but the problem with "what time I have left" is that I am (I suppose fortunately) unable to quantify that

 

[Munroast]

It all seems like a lot of effort to me - and, if it were me, I suspect I would probably decide that I had better things to do with what time I have left!

says a man with 60,000 posts on the forum -

Getting a solar system up and running and making the most of it is very interesting

 

[JohnW2]

says a man with 60,000 posts on the forum -

Almost! However, it's a matter of (individual) prioritisation - which, in context, means that, if I had a PV/battery system (which I never will), posting forum messages would probably be one of those "better things that I had to do with what time I had left" than would spending the time trying to save a bit of money!

Getting a solar system up and running and making the most of it is very interesting

I agree, as an academic or intellectual exercise, and that is,, indeed, the reason I participate in these discussions. However, my comment was directed at eric (and people like him), and it would seem that (like many others) his interest is not really 'academic'/'intellectual' but, rather, is about 'saving money' - and I do feel that, particularly for people as old as eric and myself, unless one is in a very difficult financial position,there are probably better things for us to do with "what time we have left" than trying to save a little money.

 

[ebee]

JohnW2, perhaps me an thee and Eric etc are ancient enough to be, by nature, members of the "save a shilling" generations of humans on this planet, we saw it in our parents and grandparents and at school they beat it into us with a big stick. We can`t really be owt else, we have a natural inbuilt loathing of waste.
We had expertise in make do and mend and could almost make owt with nowt.


Back in the early 80s some of our workmates had a little saying - We The Unwilling.

We the unwilling,
attempt the impossible for the ungrateful,
we have done so much with so little little for so long,
that we are now qualified to do anything with nothing.
That was our little motto, a bit tongue in cheek though!

 

[ericmark]

I am afraid, statistics was never my strong point. I remember there were three, mean, mode, and medium and then after that it is all a bit hazy.

And how to use solar and batteries is more down to statistics than simple maths, as although my software for solar tries to predict the weather, no one has really been able to do that very well.

Next is the control, I can set a reserve on the battery, so 10% is left for emergencies, and I can program it to charge from the mains at a set time. i.e. when I have off-peak, but not yet found a way to only 50% charge from grid, I must ask the installer. But also need to find what my options are with tariffs, the 8.95p/kWh I had with British Gas off-peak was clearly better than the 17.1p/kWh Octopus Flux offer, however on the peak rate, 28.5p/kWh Octopus offer is better than the 31.31p/kWh from British Gas, the worry is the 4pm to 7pm 39.9p/kWh.

17.1-10.54=6.56p/kWh loss is better than the 8.95p if I end up re-exporting it. But also 10.54p is a lot less than the 15p I get now, and it seems the suppliers just like making the maths a problem, and I reach out to @Munroast who it would seem has the same problem. Hopefully once worked out, we can just sit back?

There is between now and June 30th, going to be a lot of people, needing to do the maths. They will need to decide, is off-peak economy 7 worth it? Again, clearly not in the summer, but as a year round thing. In the same way as I looked at buying at 8.95p and then giving away later in the day, they have to decide if 24/7 heat, or heat as and when required is the order of the day.

And I do not understand our need for a temperature in the house. This time of year, if the room is 17ºC, I feel fine, but winter I want at least 20ºC, so I turn down thermostats in the summer. But this needs a different thread if to be discussed.

 

[StephenStephen]

I tend to think of peak import rate as almost irrelevant - with a battery I'd never want to be importing at that time...

 

[ericmark]

I tend to think of peak import rate as almost irrelevant - with a battery I'd never want to be importing at that time...

I am assuming you mean out of three, with off-peak, day rate, and peak rate? The problem is once set up, as @JohnW2 has said, we want to forget it. I could on a poor day charge the battery will day rate, so no draw 4pm to 7pm, but likelihood is I would not realise.

4th April 2024 to 15th October we were charging 2.88 kWh (26p) every night so it would not run out before the sun started producing, after 15th October that went to 5.76 kWh (52p). This was OK until March, although we were exporting for no payment what we had imported, not all of it, until April when we were loosing £16 a month.

Since flux pays for export, it would be a 38p per day loss, so £11.71 a month loss. The problem is to move to Flux payment drops from 15p to 10.54p it seems looking at pennies, well we are, but when I look at a month rather than a day, then I see winter bill raise by £20 unless I go off-peak.

 

[StephenStephen]

Sorry, I can't quite understand what you're meaning here.
What's the usable capacity of the battery? - maybe that will help me understand...

 

[JohnW2]

JohnW2, perhaps me an thee and Eric etc are ancient enough to be, by nature, members of the "save a shilling" generations of humans on this planet, we saw it in our parents and grandparents and at school they beat it into us with a big stick. We can`t really be owt else, we have a natural inbuilt loathing of waste. We had expertise in make do and mend and could almost make owt with nowt.

All true - but, despite that, 'tis I, a member of that generation, who has been suggesting that in the twilight days of our life, we might feel that there are things we would like to do with the remainder of our time (however much that be) than to worry about "saving shillings".

Having said that, as I often say, for a long time now (probably since my early 60s, maybe earlier), I would not have dreamed of 'investing' in some technology that was going to leave me financially worse off for the next 5-10 years, even if there were a prospect of financial benefit beyond that (if I were still around!). Indeed, I might even be 'superstitious' enough to have regarded that as 'tempting fate' !

Kind Regards, John

 

[ebee]

I am afraid, statistics was never my strong point. I remember there were three, mean, mode, and medium and then after that it is all a bit hazy.

Indeed, one of my well known sayings is "Average - is probably the most dangerous word in the Universe!" - which "average" are we referring to?
Mean/Medium/Mode, RMS, GMS, they are all averages of some type and often if we consider them all and perhaps with standard deviations of the population/non-population types , then, only just then we might actually have something useful to refer to.
Any of those on their own can be deceptive. Average wages etc etc is one such example. Just ask a politician and don't get me started on "percentages" either! It is easy to be deceived and indeed also easy to deceive ourselves!