On-grid domestic battery storage

NigeWick

Martyn1981 wrote: »

pothole in't road!

Luxury. We dream of a pothole in't road. We have to make do with a dust bath after t' sparrers have been in it.

zeupater

NigeWick wrote: »

Luxury. We dream of a pothole in't road. We have to make do with a dust bath after t' sparrers have been in it.

.... But you try n'tell t'young people of t'day that... 'nd they won't believe ya'

HTH
Z

Martyn1981

Big battery news, or big news about batteries, boy the English language is fun.

Sonnen who have batts in 10's of thousands of homes already have been bought by Shell. Hopefully that's good news, and Shell wants to encourage us to make better use of our RE???????

Shell Acquires sonnen!

1961Nick

Exiled_Tyke wrote: »

Factor in the cost of capital and the benefits are wiped out. For example currently 2.7% interest is available on savings (five year fixed). After the 14 1/2 years the £3,300 investment would be worth £4,800.

Also take into account efficiency losses and battery degradation and I really can't see this adding up.

However, if you then factor inflation in, your £4,800 is worth about £3,300 in real terms. Back to square one!

zeupater

1961Nick wrote: »

However, if you then factor inflation in, your £4,800 is worth about £3,300 in real terms. Back to square one!

Hi

Which is exactly the point that ET was making in the referenced post which was itself addressing 'mmmmikey''s use of energy inflation at an annualised 3% in the battery payback calculation .... if loss of opportunity equates to rate of inflation then they cancel each other out, so there's no reason to raise inflation at all other than to help justify a decision on grounds employing erroneous logic, which seems to be the agreed conclusion!

HTH
Z

1961Nick

After 3 years of watching battery prices I decided to take the plunge.

As others have said, the financial case is still weak at best, but there's now a reasonable chance of coming out on top - more so if energy prices keep outstripping inflation.

Anyway, I've bought a Sofar ME3000SP & 4 x Pylontech US2000 Plus batteries. 9.6kWh total storage of which 8.2kWh is useable.

Last year we exported 2700kWh & I've a reasonable chance of using most of that this year - although I might need another battery to achieve it.

Payback is currently 13 years assuming the lost ROC would have been offset by inflation over that period. Payback is obviously quicker if energy prices rise.

I will also consider a smart meter & a traffic light tariff when they become available although the maths on that are not really positive at the moment. The problem is that each kW charged/discharged has a capital cost of about 8.5p that needs to be added to the cost of the cheap imported energy (8p/kWh?). 16.5p is currently 3.27p more than I'm paying my supplier. The savings on the amber tariff wouldn't be enough to offset that.

1961Nick

zeupater wrote: »

Hi

Which is exactly the point that ET was making in the referenced post which was itself addressing 'mmmmikey''s use of energy inflation at an annualised 3% in the battery payback calculation .... if loss of opportunity equates to rate of inflation then they cancel each other out, so there's no reason to raise inflation at all other than to help justify a decision on grounds employing erroneous logic, which seems to be the agreed conclusion!

HTH
Z

But you still need to factor energy price inflation into the calculation if you believe energy prices will rise?

My assertion was that other than the initial outlay, there isn't any opportunity cost given that inflation/interest rates are currently about equal. Also the savings that you are making from day 1 of the installation are effectively repaying that capital outlay.

The calculation actually becomes so complex with so many variables that you can make a compelling case either way for battery storage.

A simplistic calculation would be;

6000 cycles x 8.2kWh x 13.23p = £6509

That's £2300 more than the batteries & inverter cost so there's a realistic probability of payback.

zeupater

1961Nick wrote: »

After 3 years of watching battery prices I decided to take the plunge.

As others have said, the financial case is still weak at best, but there's now a reasonable chance of coming out on top - more so if energy prices keep outstripping inflation.

Anyway, I've bought a Sofar ME3000SP & 4 x Pylontech US2000 Plus batteries. 9.6kWh total storage of which 8.2kWh is useable.

Last year we exported 2700kWh & I've a reasonable chance of using most of that this year - although I might need another battery to achieve it.

Payback is currently 13 years assuming the lost ROC would have been offset by inflation over that period. Payback is obviously quicker if energy prices rise.

I will also consider a smart meter & a traffic light tariff when they become available although the maths on that are not really positive at the moment. The problem is that each kW charged/discharged has a capital cost of about 8.5p that needs to be added to the cost of the cheap imported energy (8p/kWh?). 16.5p is currently 3.27p more than I'm paying my supplier. The savings on the amber tariff wouldn't be enough to offset that.

Hi

You'll likely find that with that setup a household with average UK demand would look something like import levels of ....

Base 3200kWh
PV 2250kWh
Battery 1000kWh

.. and if using battery & off-peak charging the import moves from 1000 to 1150kWh with only around 470kWh being at the cheaper unit cost ....

If you have a very sophisticated energy management system the energy imports could move up towards around 1300kWh, with around 230kWh of that being at the higher unit rate .... However, I'm not currently aware of any domestic battery solution that has this level of sophistication on energy optimisation as standard or even as an option! ...

.... By the way, you'd still be exporting around 1200kWh/year of your PV generation using this scenario as you'd simply not have sufficient demand or storage during the summer months!

Apply the your own unit costs & the result should be pretty accurate.


HTH
Z

(Model - V1r25)

zeupater

1961Nick wrote: »

But you still need to factor energy price inflation into the calculation if you believe energy prices will rise?

My assertion was that other than the initial outlay, there isn't any opportunity cost given that inflation/interest rates are currently about equal. Also the savings that you are making from day 1 of the installation are effectively repaying that capital outlay.

The calculation actually becomes so complex with so many variables that you can make a compelling case either way for battery storage.

A simplistic calculation would be;

6000 cycles x 8.2kWh x 13.23p = £6509

That's £2300 more than the batteries & inverter cost so there's a realistic probability of payback.

Hi

The opportunity would be provided by keeping the money invested & having no capital outlay - if you include inflation to make the payback look better, then you should logically net this against lost interest. The issue here is that in the absense of crystal balls any attempt to predict inflation is pure speculation ... that's why financial comparisons/justifications are normally made on either a current cost basis or at a particular ecomomic level (say 2012 economics etc).

Regarding the cycles ... if 6000 cycles is the count to the standard 70% level then the average storage over those cycles shouldn't be 8.2kWh, on a simplistic basis it would need to be the average over those 6000 cycles, so ~7kWh (8.2*85%) .. of course, this is still incorrect when you consider that battery efficiency losses result in additional energy purchases - likely averaging 15%+ on a round trip basis (including 'vampire' standing losses!) .... just these basic observations reduce the simplistic calculation posed from £6500 to around £4700 (6000x7x(13.23*0.85)=£4723).

Additionally, there's a very substantial question around what tariffs you would use for comparison - for example, we have a no standing charge tariff which works well with solar & no battery, so would logically also work with a battery ... however, it's a single rate offering, so to move a low usage (/import) household to use cheaper off-peak energy through battery storage on a tariff which includes standing charges would cost us substantially more even though both peak & offpeak unit rates would be cheaper!

HTH
Z

1961Nick

zeupater wrote: »

Hi

The opportunity would be provided by keeping the money invested & having no capital outlay - if you include inflation to make the payback look better, then you should logically net this against lost interest. The issue here is that in the absense of crystal balls any attempt to predict inflation is pure speculation ... that's why financial comparisons/justifications are normally made on either a current cost basis or at a particular ecomomic level (say 2012 economics etc).

Regarding the cycles ... if 6000 cycles is the count to the standard 70% level then the average storage over those cycles shouldn't be 8.2kWh, on a simplistic basis it would need to be the average over those 6000 cycles, so ~7kWh (8.2*85%) .. of course, this is still incorrect when you consider that battery efficiency losses result in additional energy purchases - likely averaging 15%+ on a round trip basis (including 'vampire' standing losses!) .... just these basic observations reduce the simplistic calculation posed from £6500 to around £4700 (6000x7x(13.23*0.85)=£4723).

Additionally, there's a very substantial question around what tariffs you would use for comparison - for example, we have a no standing charge tariff which works well with solar & no battery, so would logically also work with a battery ... however, it's a single rate offering, so to move a low usage (/import) household to use cheaper off-peak energy through battery storage on a tariff which includes standing charges would cost us substantially more even though both peak & offpeak unit rates would be cheaper!

HTH
Z

6000 cycles @ 85% DOD is accurate.

The batteries are rated down to 90% DOD but the maximum inverter setting is 85%.

Losses don't appear to be anywhere near 15% but I don't have enough data yet to be sure of a figure. The 'vampire' standing loss is 10w.

Even on your miserly figures, the chance of breaking even is now a reality......unless the inverter packs in after 10 years!:sad: