Battery or no Battery - Please help me decide!

Alnat1

@Petriix How did you "accurately assess" ROI in a wildly fluctuating energy market? Do you mean your guess came up with different numbers to those who recently installed batteries?

ggmf

Petriix said:

And that's because the only people who have batteries are the ones who don't bother accurately assessing the ROI, or have very unusual usage. 

The ROI comment on batteries keeps coming up, what is a good ROI? 

Our install was 'just in time', before it all went crazy, where supply has reduced and prices are through the roof due to demand. 

I did not look at ROI on the battery, I looked at ROI on our system as a whole, and that was based on our then 'fixed' unit prices. Once our 'fixed rate' ended (it was not cost benifcial to fix again at the time), we were moved onto the variable rates, that has seen unit prices increase 3 times so far since install, to its current rate.

Our current 'system wide' ROI, for electricity only, based on current unit cost is now exactly 5 years, it was obviously more than that when I did our original calculations, this '5 years' will reduce further once unit cost increases are applied in the future.

The 5 year figure does not include the savings from reductions to our gas use, (gas costs have increased too!), by diverting excess solar (when available) to the hot water tank after the battery is charged, or the measly income from SEG payments, neither of which were included in our original ROI calculations.

Would I have a battery? Absolutely
Would installing 2 batteries been cost effective? It was not for us at the time.

So did I bother assessing the ROI? Yes, not sure anybody can assess accurately though, to many variables.

Exiled_Tyke

ggmf said:

Petriix said:

And that's because the only people who have batteries are the ones who don't bother accurately assessing the ROI, or have very unusual usage. 

The ROI comment on batteries keeps coming up, what is a good ROI? 

Our install was 'just in time', before it all went crazy, where supply has reduced and prices are through the roof due to demand. 

I did not look at ROI on the battery, I looked at ROI on our system as a whole, and that was based on our then 'fixed' unit prices. Once our 'fixed rate' ended (it was not cost benifcial to fix again at the time), we were moved onto the variable rates, that has seen unit prices increase 3 times so far since install, to its current rate.

Our current 'system wide' ROI, for electricity only, based on current unit cost is now exactly 5 years, it was obviously more than that when I did our original calculations, this '5 years' will reduce further once unit cost increases are applied in the future.

The 5 year figure does not include the savings from reductions to our gas use, (gas costs have increased too!), by diverting excess solar (when available) to the hot water tank after the battery is charged, or the measly income from SEG payments, neither of which were included in our original ROI calculations.

Would I have a battery? Absolutely
Would installing 2 batteries been cost effective? It was not for us at the time.

So I did bother assessing the ROI? Yes, not sure anybody can assess accurately though, to many variables.

Five years at current prices seems about right.  I reckon my battery is saving me over £600 a year currently.   As I've mentioned on these boards before. When I bought the battery I thought it might just break even but the longer these current prices last (and of course I hope they don't as much as anyone else)  the better the investment is looking.  Like the investment in Ripple it's not even necessarily about getting the best return.  I see this as a hedge, locking in an amount of energy at a fixed cost.  So for me it was partly about taking some risk out of energy prices.   If prices drop I'll be as relieved as everybody else and I still won't regret buying the battery as it's doing exactly what I want it to do. 

andyg9053

Second house with solar, installed 6kw, Tesla and gateway, zappi and Eddie. 17k all in last year. On Octopus go as obviously have ev. Seg is a pittance so I use Eddie and nightrate for hot water.  According to Tesla in 12 months it has saved me 2100. Payback is 8 years, in addition I haven’t bought petrol/diesel and driven 12k miles, so saved a few quid there as well. My main reason was I had cash in bank getting me nothing, this may have an effect on my grandkids future.

Petriix

Alnat1 said:

@Petriix How did you "accurately assess" ROI in a wildly fluctuating energy market? Do you mean your guess came up with different numbers to those who recently installed batteries?

Well, when I ordered the battery I made some assumptions and came up with a ballpark figure of saving about £500 per year. But, while waiting for delivery (for over 6 months), I analysed my smart meter data and modeled how much I could have saved. 

The upshot was that I could shift lots of my usage into the off-peak window without the need for a battery. My peak grid import is likely to total around 1,000kWh in 2022. If a battery removed half of that and shifted the other half from the peak rate at 24.25p into my 5p rate, the saving would total just £217.50.

At next year's prices of 12p and 40p that could be a £340 saving. That's with zero peak import, which is pretty difficult to achieve in practice.

If my peak usage was double then it would make sense. A £680 saving would be a ROI in under 7.5 years on a £5k installation. However, that would be a gamble dependent on a) prices staying that high; and b) Octopus Go enduring.

It is difficult to anticipate how solar will affect your usage. Having access to detailed data for half-hourly generation, consumption, import and export has given me insight that shattered some of my assumptions. 

Reed_Richards

I'm on deemed export so rather ignorant but I found a table of SEG rates as they were earlier this year:
 https://solarenergyuk.org/resource/smart-export-guarantee/
 
They are generally pretty paltry so should you base your battery/no battery decision on the basis of one company offering a good SEG rate on one particular tariff? 

[Deleted User]

If you are going to choose a battery then my 2p’s worth would choose one where you initiate a discharge to the Grid when SEG prices are high. (See Octopus Agile Outgoing)

If you want a battery with an islanding facility that is connected to your main consumer box then you need prior DNO approval. The DNO will want to be satisfied that in the event of a grid failure that the battery and the solar array will disconnect from the grid in the prescribed timescale. The Powerwall 2 has this facility but the Gateway is an additional cost.

Part of any DNO review will be the ability of the grid to take the export load. Some applicants have been disappointed when a site export limitation has been imposed.

ispookie666

It's always fascinating when ROI is the first thing people harp about when talking about solar, batteries, ASHP but hardly do the same for white goods, cars etc... 

EcoScruples

Hmm, if your main aim is payback then at the moment everything screams no to a battery.

Since my June install I've used 70% of what I've generated with the other 30% going to the grid.
Without a battery those figures would have been reversed so although the agile export payments were great during the summer there's no guarantees they will stay that high.

I am only just getting my eddi installed next week so have been running the immersion by hand when power was available from the panels.
Having hit water during the summer without having to keep an eye on the sunshine will be great.

I am looking at a back up box to run on battery in case of power outages, again, peace of mind.

Ultimately you'll know already if you want a battery.

Screwdriva

Petriix said:

Alnat1 said:

Keep reading, and you'll see it's as I said, the only people who say no to batteries are the ones who don't have them 

And that's because the only people who have batteries are the ones who don't bother accurately assessing the ROI, or have very unusual usage. 

Believe me I would have batteries if they made financial sense. I cancelled my Givenergy order (at under £4k for 8.2kWh installed) because the numbers couldn't possibly add up for me.

However, my advice is to do the sums and make an informed decision. 

Well said!  While not every use case is the same (there is no panacea), most households only hurt their financial case by getting a battery. Really heavy evening users, EV + Heat pump households are the only exceptions, as are those as risk of regular blackouts, but even there, the upfront spend on 15+ kWh of storage is hard to digest! 

Let's not forget that batteries, even from the best manufacturers, come with a 10 year warranty and added complexity in the form of external controllers (in some instances). This means that it may very well be that halfway through the life of your PV system, say 15 years or so, your battery and/ or controller may need replacement, starting the ROI clock once again. As someone who has installed off grid solar/ wind hybrid solutions, I would never believe anyone who claims their battery will last the duration of their PV system - it's just well intentioned inexperience talking.  

Rather than listen to any opinion, I always recommend starting with this calculator and working backwards with actual numbers. You won't regret the few minutes it takes to remove all subjectivity from the equation.