Solar and Battery Storage are they viable ?

[DrFfybes]

Well funduffer your calculations seem to completely exclude consideration of the solar panels other than to say it’s not worth using them !.

We have 4KW solar system and it can fully charge our 8.2Kw battery (at zero cost),

Not zero cost, you get paid for your exported energy that went into the battery, and wouldn't have earned interest on the cost of the panels?

I read FD as saying the best thing was to export the solar and charge the batteries overnight, IF you could get overnight supply cheaper than the daytime export rate.

Using a cheap off peak tariff might be good in the winter months, though the new Octopus Flux tariff you can get paid 19.3p for your export and 31.4p during the 16:00-19:00 peak time slot. There are issues though with smart meters, loss of inflation proof FIT payments and the fact that it’s a variable tariff and can be varied by them any time they see fit – so we are still on their standard variable tariff (SVT) tariff ATM.

Hmm, now that's where battery could be economical if you were allowed to charge overnight on a cheap flex rate circa 7p and export at the peak at 41p, then your 8kW battery would make you £870 pa, probably a good 10% return, given the right software. You would still use the battery as a buffer for the solar (see below) but making sure it was charged fully by 4pm.

What you aren't doing in your maths is decoupling the battery and solar element paybacks. On most tariffs batteries increase the payback time compared to solar alone and a decent export price. The complication is for the brief periods you draw high current, when you are still importing at 30p/unit and then the kettle boils or the hot water switches off and you are back to exporting. In these periods the battery decouples you from the supply so you consume more export rate energy then without it.

Paul

[PrefInvestor]

I read FD as saying the best thing was to export the solar and charge the batteries overnight, IF you could get overnight supply cheaper than the daytime export rate.

Hmm, now that's where battery could be economical if you were allowed to charge overnight on a cheap flex rate circa 7p and export at the peak at 41p, then your 8kW battery would make you £870 pa, probably a good 10% return, given the right software. You would still use the battery as a buffer for the solar (see below) but making sure it was charged fully by 4pm.
Paul

Well DrFfybes the way Octopus Tariffs work any tariff you are on generally defines both your import and export prices, so I suspect that you cant be on the Octopus Economy 7 tariff for import and the Octopus Outgoing Fixed Tariff for export at the same time – though I haven’t asked the question. And apart from that one Octopus Export Guarantee tariff all the other export guarantee tariffs around right now are more like 5p – which is less than I get for FIT export, so not attractive.

Octopus DO have a smart tariff specifically designed to do what you describe though, this is Octopus Flux. This provides a low cost early morning 02:00-05:00 battery charging slot (cost 18.18p per Kw, export paid at 7.18p during this slot) and a peak time slot (16:00-19:00) when you are paid a premium rate for your export (price paid 31.41p, import charged at a hefty 42.41p during this slot). The rest of the day you are charged 30.3p for import and are paid 19.3p for any export.

Working out how much you can save by employing these slots and your solar / battery kit to take maximum advantage is a complex problem – believe me I’ve tried to do so. But it SHOULD be profitable, though Id have to give up my FIT export and get smart meters to try it – which Im reluctant to do.

ATB

Pref

[funduffer]

I read FD as saying the best thing was to export the solar and charge the batteries overnight, IF you could get overnight supply cheaper than the daytime export rate.

Hmm, now that's where battery could be economical if you were allowed to charge overnight on a cheap flex rate circa 7p and export at the peak at 41p, then your 8kW battery would make you £870 pa, probably a good 10% return, given the right software. You would still use the battery as a buffer for the solar (see below) but making sure it was charged fully by 4pm.
Paul

Well DrFfybes the way Octopus Tariffs work any tariff you are on generally defines both your import and export prices, so I suspect that you cant be on the Octopus Economy 7 tariff for import and the Octopus Outgoing Fixed Tariff for export at the same time – though I haven’t asked the question. And apart from that one Octopus Export Guarantee tariff all the other export guarantee tariffs around right now are more like 5p – which is less than I get for FIT export, so not attractive.

Octopus DO have a smart tariff specifically designed to do what you describe though, this is Octopus Flux. This provides a low cost early morning 02:00-05:00 battery charging slot (cost 18.18p per Kw, export paid at 7.18p during this slot) and a peak time slot (16:00-19:00) when you are paid a premium rate for your export (price paid 31.41p, import charged at a hefty 42.41p during this slot). The rest of the day you are charged 30.3p for import and are paid 19.3p for any export.

Working out how much you can save by employing these slots and your solar / battery kit to take maximum advantage is a complex problem – believe me I’ve tried to do so. But it SHOULD be profitable, though Id have to give up my FIT export and get smart meters to try it – which Im reluctant to do.

ATB

Pref

I read FD as saying the best thing was to export the solar and charge the batteries overnight, IF you could get overnight supply cheaper than the daytime export rate.

Precisely so.

On tariffs, you should remember that your electricity supplier and your export refunder do not need to be the same company. Scottish Power pay 12p per unit for their export SEG, but you don't have to have Scottish Power as your electricity supplier.

I use Scottish Power for export (at 12p per unit) and Octopus Go for my supply (7.5p off peak and 38p during the day) for 1 year from last September. The Go rates are 9.5p off-peak and about 30p during the day if you signed up now.

I am not familiar with Octopus Flux, but it looks worth a look. There is also intelligent Octopus. I need to get my head around these when my 1 year fix is up in September.

Also the OP is considering purchasing solar, so FIT is not relevant as it is no longer available to new solar owners - it is SEG rates you need to look at.

FD

[DrFfybes]

[
Octopus DO have a smart tariff specifically designed to do what you describe though, this is Octopus Flux. This provides a low cost early morning 02:00-05:00 battery charging slot (cost 18.18p per Kw, export paid at 7.18p during this slot) and a peak time slot (16:00-19:00) when you are paid a premium rate for your export (price paid 31.41p, import charged at a hefty 42.41p during this slot). The rest of the day you are charged 30.3p for import and are paid 19.3p for any export.

Pref

I get that you have to be on one tariff, but what I don't understand (possibly as I'm still waiting for the soalr/battery kit to arrive on the 24th) is how much control you have over the battery - ie when it charges and discharges.

We're on the standard Octopus rate in preparation for going on to Outgoing Fixed (I think), but as we don't eat until 8pm then the Flus might actually be better for us, as the export is slightly higher days time and a lot higher peak assuming we can make the battery do that.

There's an old saying - "If I have to explain, you wouldn't understand". Can we change that to "I thought I understood, until everyone explained it"

Paul

[csearle]

Did you have to handle the anti-islanding yourself or are these gadgets smart enough now to do that for you?

Well my electrician mate John, whose job this was, did the installation. I just helped with the commissioning. Fact is that this thing is basically a black box with an instruction sheet. I rather imagine that is meets requirements because it would probably not have been available to buy otherwise. (Weak argument I realise.)

It was one of these (the one on the left).

Chris

[PrefInvestor]

Well I agree that funduffer is quite correct when he says that a good strategy is to charge your battery at some cheap rate and make money by exporting what you’ve stored at a higher rate, if you can find tariff(s) that let you do that. In theory the Octopus Flux tariff does exactly that but the different import/export pricing in the different time periods and the characteristics of your solar (including variations in solar production as a function to the time of year) and various battery characteristics make it difficult to calculate whether/how much you might save.

Funduffer is also correct when he points out that if you have solar and/or a battery and your electricity tariff only deals with import pricing (even if that pricing varies by time of day eg economy 7) then you can also be on a smart export guarantee tariff with any market supplier to get paid for any electricity that you export. That is provided that you give up any rights you may have to FIT export payments and have smart meters installed. There are potentially tricky decisions involved here for someone like myself who is on FIT and are receiving deemed export payments as we don’t have a smart meter, just one of which is that FIT payments rise with RPI every year and that lasts for 20 years from the date that your FIT contract started.

Octopus Go is a most excellent tariff offering a long overnight charging slot at a low price, but regrettably is now restricted to EV car owners. You can be on Octopus Go and a smart export tariff I know as my son does exactly that. But buying an EV is a very expensive way to get on a good electricity tariff !.

As for the question of what features are available to control your battery this is totally dependent on the make of battery that you own and the software facilities provided. I have a GuvEnergy battery and its default mode is for the battery to be charged with any excess solar not being used to power the house and if there is no solar then any stored battery power is used to supply the house, the grid only being used if no solar or battery power is available. However you can in addition activate facilities that will charge the battery from the grid to a certain percentage or discharge the battery outputting to the grid and these events can be set to happen on a timed basis, either one off or repeating regularly. The GivEnergy battery is also capable of being set to work in conjunction with various Octopus tariffs, most notably Outgoing Octopus/Octopus Agile, and set to charge or discharge the battery in the half hour slots used by this tariff. However note that facilities offered by other battery suppliers may be very different. You need to check this out before buying !.

ATB

Pref

[servodude]

Did you have to handle the anti-islanding yourself or are these gadgets smart enough now to do that for you?

Well my electrician mate John, whose job this was, did the installation. I just helped with the commissioning. Fact is that this thing is basically a black box with an instruction sheet. I rather imagine that is meets requirements because it would probably not have been available to buy otherwise. (Weak argument I realise.)

It was one of these (the one on the left).

Chris

-Simple:
Modulat desian, single person con carry and install it.

Pretty compact looking system though