Solar Inverter Query

Telegraph_Sam

@Qyburn. This is fundamental. I have solars but no batteries and no EV. FIT generation gets credited by Scot Power whilst exports go to Octopus External Fixed. I'm on Tracker.
If I understand you correctly, my export is quite independent of my consumption, no trade-off. If such be the case then it doesn't make any difference whether I do the heavy lifting in the morning, noon or night???
I don't consciously  go in for deliberate load shifting but according to Compare my Tracker results are similar to Agile in the med and longer terms. Contrary to expectations.

Qyburn

Telegraph_Sam said:

@Qyburn. This is fundamental. I have solars but no batteries and no EV. FIT generation gets credited by Scot Power whilst exports go to Octopus External Fixed. I'm on Tracker.
If I understand you correctly, my export is quite independent of my consumption, no trade-off. 

No, your generation FIT payments are independent of consumption. 

Let's give two examples, in each case you generate 4kWh, FIT generation 27p, Export 15p, import 22p. 

(a) Use 4kWh to run your tumble dryer while there's surplus solar ..
FIT payment 4 x 27p       = £ 1.08
Export payment              =  £ 0.00  (because it's all used by the tumble dryer)
Import cost                      = £ 0.00  (because solar has covered consumption 

(b) Run tumble dryer later when there's no solar ..
FIT payment 4 x 27p        = £ 1.08
Export payment 4 x 15p  = £ 0.60  (sunny, tumble dryer not running, production is exported)
Import cost 4 x 22p         = £ 0.88   (later on, no sun, consumption needs to be imported)

matt_drummer

I don't understand.

You have had solar panels for about 10 years and you have recently given up your deemed export to go onto metered export.

Yet you don't understand how it works and are now asking really basic questions about how to make best use of your generated electricity?

Surely you should have worked all this out before switching to metered export?

Telegraph_Sam

Yes, with foresight I would. I hope you can help.

Telegraph_Sam

Putting it at its very simplest:
If I have solar panels but no battery.
And I get FIT credits from Scot Power and SEG payments from Octopus Export Fixed.
> Is it to my advantage, or to my disadvantage, to time running the proverbial washing machine to coincide with max sunlight, or does it make no difference whether it is light or dark?
Tks

matt_drummer

The best time to use electricity is when it is cheapest.

Using solar costs you 15p per kWh as that is what you lose by not exporting.

If you can import for less than 15p per kWh then that is cheapest.

If not, it is cheapest to use your solar generation rather than export it.

Telegraph_Sam

Helpful,tks. I forgot to mention that I am with Tracker and the current import cost seems to fluctuate daily @ around 20 p/kWh. So consumption wise there should be no difference what time of the day I do the "washing".

That then means that according to your rule I should look to make max use of the solars at an opportunity "cost" of 15 p as long as the supply is there, i.e. midday / early afternoon. The practical difficulty is of course to determine how much my panels are generating at any particular point in time, but going to this degree of complexity is not worth it. The default will be the automatic switch to normal import supply when the solars are exhausted by the fading light.

I hope this is correct as far as a layman's interpretation goes.

matt_drummer

An example

If your washing machine consumes 2kW and the panels are generating 1kW then you will import 1kW.

Your total cost for 1 hour at that power level would be 35p (1kWh at 20p and 1kWh at 15p)

If you did it all from solar it would cost 30p and if it was all from import it would be 40p

As you generally get paid less for your exports than it costs you to import then you are better off using as much of your solar generation as you need.

However, if you use most of it, that brings into question your decision to move from deemed export to metered export.

Something you should have already considered before making the decision to change.

Telegraph_Sam

Does any of that not agree with my interpretation? It seems to bear it out.

There are many things which in retrospect one could improve on with the benefit of hindsight.  The unknowns that you don't know you don't know.  I doubt very much if I could have got to this stage without first going the SEG export route. And certainly getting 15 p for exported units was / is a large attraction regardless of when I took the decision.

matt_drummer

Telegraph_Sam said:

Does any of that not agree with my interpretation? It seems to bear it out.

There are many things which in retrospect one could improve on with the benefit of hindsight.  The unknowns that you don't know you don't know.  I doubt very much if I could have got to this stage without first going the SEG export route. And certainly getting 15 p for exported units was / is a large attraction regardless of when I took the decision.

Imagine that you managed to consume all of your generated electricity.

Your export income would be £0.00 with metered export

However, if you had stayed on deemed export you would be paid for 50% of your total generated electricity even if you had used all of it.

There is a self consumption level where you would be better off on deemed export.

The more you consume yourself the closer you get to being worse off on metered export than deemed export.

We don't know how much you generate and how much you export, but if you do, you can do the calculation if you haven't already done it.

But, having switched to metered export it is too late. 

It is still in your best interests now to use as much of what you generate to cover normal household consumption when your imported cost is over 15p per kWh.