Solar Battery - Yes/No?

Screwdriva

ABrass said:

If we get to the same level of penetration then the SEG rates will fall. That's not going to be next year, or the one after. But if you're planning a 10 year investment then just looking at past prices is a poor guide.

It also assumes you can get Octopus Agile. Right now if you're not an octopus customer now I don't believe you can become one on Agile.

I try not to get into the prediction game but it's safe to say that I see no reason a variable SEG tariff will be anything lower than 50% of a variable import tariff. Unless you think electricity prices are going to drop dramatically in the foreseeable, I'm not certain what your point is? Let's assume your belief is that prices will correct drastically for some reason - it is relatively easy to plan for this with a panel/ inverter purchase today and purchase a more dense, efficient, inexpensive and evolved battery in a few years. 

silverwhistle

Reed_Richards said:

Above is a calculation of the payback time for a washing machine; what is the payback time for a vacuum cleaner?

Or a new kitchen, which would be a similar (or greater) cost to my PV installation?

QrizB

Screwdriva said:

... I see no reason a variable SEG tariff will be anything lower than 50% of a variable import tariff.

Two years ago, in September 2020, the capped variable import tariff was 17.81p/kWh and (outside the evening peak) Outgoing Agile was averaging about 5p/kWh.

ABrass

Screwdriva said:

ABrass said:

If we get to the same level of penetration then the SEG rates will fall. That's not going to be next year, or the one after. But if you're planning a 10 year investment then just looking at past prices is a poor guide.

It also assumes you can get Octopus Agile. Right now if you're not an octopus customer now I don't believe you can become one on Agile.

I try not to get into the prediction game but it's safe to say that I see no reason a variable SEG tariff will be anything lower than 50% of a variable import tariff. Unless you think electricity prices are going to drop dramatically in the foreseeable, I'm not certain what your point is? Let's assume your belief is that prices will correct drastically for some reason - it is relatively easy to plan for this with a panel/ inverter purchase today and purchase a more dense, efficient, inexpensive and evolved battery in a few years. 

That's a failure of your imagination. 

https://www.theguardian.com/environment/2021/mar/25/australians-could-be-charged-for-exporting-energy-from-rooftop-solar-panels-to-the-grid

We've seen market prices where people have been paid to use power in some tarrifs. When wind and solar gets to be a larger fraction of the market then the value of your export power during a period of glut is zero.

It is not a simple decision with a universally correct answer for all people and use cases even with the same assumptions on price rises.  My point is that you've come up with an answer for you that fits your assumptions and experience. That doesn't mean it's right for everyone else 

Screwdriva

ABrass said:

That's a failure of your imagination. 

Or yours. 

Australia's predominant energy source is coal. Ours is gas. The two nation's energy mixes and where each sources its fuels from, couldn't be more different. Not to mention the lens through which fossil fuels are viewed - take it from this former Aussie, they love their coal.

Let's review your hypothesis when wind and solar actually do represent a larger share of the UK mix than the 20-30% they have averaged on the best of days. 

ABrass said:

It is not a simple decision with a universally correct answer for all people and use cases even with the same assumptions on price rises.  My point is that you've come up with an answer for you that fits your assumptions and experience. That doesn't mean it's right for everyone else 

I've never claimed a one size fits all answer. But I do not accept that the upfront cost of a battery makes financial sense for new solar customers, as the calculator above highlights, when there is zero indication that any of your predictions? are anything but a distant possibility at best. 

HHarry

Exiled_Tyke said:

"We suspect that you have often heard conversations that go something like this: “We are spending $6 a week, or around $300 a year, at the laundromat. If we bought a washing machine for $800, it would pay for itself within three years. That’s well worth it.” You have just encountered the payback rule.

A project’s payback period is found by counting the number of years it takes before the cumulative cash flow equals the initial investment. For the washing machine the payback period was just under three years. The payback rule states that a project should be accepted if its payback period is less than some specified cutoff period. For example, if the cutoff period is four years, the washing machine makes the grade; if the cutoff is two years, it doesn’t.

We have no quarrel with those who use payback as a descriptive statistic. It is perfectly fine to say that the washing machine has a three-year payback. But payback should never be a rule."

I completely agree with this, so I’m not sure why there’s a disagreement - I certainly hadn’t stated that payback was a ‘rule’ and I don’t think Screwdriva had either.

it’s like the Safe Withdrawel Rate on the pensions forum, which is often quoted as a rule, but would leave you in trouble if used as such.

The payback period calculation seems to be a reasonable way of quickly & easily assessing the financial benefit - with the cutoff period being the expected life of the item in terms of a physical thing.  If the washing machine is likely to die before the savings made recoup it’s cost then it probably doesn’t make a lot of sense.

 I also agree with Heed that the calculation should think about factors like repairs or inflation - more so with bigger investments.

As for assessing the payback of a vaccumm cleaner in Reeds post - it could still be financial; it’s bagless so I’ll save £x on bags over it’s lifetime.  But it could be more subjective like time - I’ll save y hours because I won’t have to sweep the floor and my time is worth £x to me.

ABrass

Screwdriva said:

Let's review your hypothesis when wind and solar actually do represent a larger share of the UK mix than the 20-30% they have averaged on the best of days. 

In 2020 renewables accounted for more than 43.1% of the UK's total electricity generated, at 312 terawatt hours (TWh). This outstripped fossil fuels over the course of a year, for the first time in the nation’s history.

https://www.nationalgrid.com/stories/energy-explained/how-much-uks-energy-renewable#:~:text=Breaking records: The UK's renewable energy in numbers&text=In 2020 renewables accounted for,time in the nation's history.

You know less than you think you do.

Screwdriva

ABrass said: You know less than you think you do.

To think I was actually taking you seriously till just now. Posting a link to article using 2020's exceptional renewable yield during COVID lockdowns as a reason why the UK will stop incentivizing solar SEG tariffs is amateur comedy.

Especially when the same article states 2021's renewable yield to our mix was actually lower than the previous year. Any guesses what 2022's contribution is going to look like? (Here's a clue: it isn't going to help your argument). 

Coastalwatch

With it being summer time and an abundance of generation, almost on a daily basis, I set the overnight charge on our batteries down to 20% during a three hour slot in the Go period to reduce the chances of importing energy unnecessarily from the Grid. It has worked well for us. However, yesterday our Inverter went down with an error code and all generation ceased at 11am and still out now while we await a call back from the Installer. Hoping to learn something today from them although, like all installers currently, they are very busy. The warranty period of the inverter has another 16 years to run.

Not knowing how long it may be before we are generating again we have no option but to import, so rather frustrating when all had been going so well. But did think to alter the battery charge back up to 95% before turning in last night so at least getting any import at  minimum rate.

Now, that's one little unexpected bonus to having batteries that had never crossed my mind prior to purchasing them. I fully appreciate it's unlikely there will ever be a surplus financial return from them but in the current climate they are certainly fun to own and quite an asset it would seem, especially so with our neighbour having booked to charge his hybrid with us tomorrow morning.

ABrass

Screwdriva said:

ABrass said: You know less than you think you do.

To think I was actually taking you seriously till just now. Posting a link to article using 2020's exceptional renewable yield during COVID lockdowns as a reason why the UK will stop incentivizing solar SEG tariffs is amateur comedy.

Especially when the same article states 2021's renewable yield to our mix was actually lower than the previous year. Any guesses what 2022's contribution is going to look like? (Here's a clue: it isn't going to help your argument). 

You said the best average over a day was 20-30%. In that quarter it was 43%.

The best day so far has been 80%, admittedly on an exceptional day but that's what the best day is by definition.

[For 2022 Q1:] Renewables’ share of electricity generation was 45.5 per cent, second only to the record 47.1 per cent achieved in the first quarter of 2020 when the UK experienced exceptionally high wind speed

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1086781/Energy_Trends_June_2022.pdf

We've probably got to the point where we're arguing rather than discussing so we should knock it on the head. But my final word on the topic is: Assuming that good export tariffs will be available indefinitely is a bad idea. We've seen other countries with high solar contribution where excess power is worthless, we will get there at some point.