On-grid domestic battery storage

70sbudgie

There seems to be a general consensus that RoI on batteries isn't good. But on the "how low can you go" board and others, there seem to be a lot of people with batteries that have achieved incredibly low imports. With typical annual import costs currently in the thousands, real world battery RoI can't be all that bad? Am I missing something, or is it to do with the detail? 

Exiled_Tyke

70sbudgie said:

There seems to be a general consensus that RoI on batteries isn't good. But on the "how low can you go" board and others, there seem to be a lot of people with batteries that have achieved incredibly low imports. With typical annual import costs currently in the thousands, real world battery RoI can't be all that bad? Am I missing something, or is it to do with the detail? 

When I added my battery I was of the view that it might pay for itself with a bit (ok, a lot) of luck.  The figures for this year have transformed that picture.  I think one of two things are going on here.  Either - there is a belief set and therefore an inertia.  The belief is that batteries can't possibly pay and that's that.  The mantra is easy and reworking the numbers takes effort.   Or and probably a lot more important, while current savings are very good, the question is how long with they last? If we have a few short years of this we will be back to the old picture quite quickly.  On the other hand if this is the new world then the investment looks good. It all depends on your perspective. 

FYI - I estimate that my full system which cost approx £10k and currently gets a FIT and export payment of about 18.5p is currently returning around £1,700 pa at current prices. 

goRt

70sbudgie said:

There seems to be a general consensus that RoI on batteries isn't good. But on the "how low can you go" board and others, there seem to be a lot of people with batteries that have achieved incredibly low imports. With typical annual import costs currently in the thousands, real world battery RoI can't be all that bad? Am I missing something, or is it to do with the detail? 

I think the logic goes along the lines of:
RoI = ((peak rate - off-peak rate)*90%* kWh per day * 365  * lifetime of batteries) / purchase price

Then
Purchase price * (1 + savings rate%) ^ lifetime of batteries

So your RoI is, say, 1.5, but your initial investment left in a savings account would have grown by 3.5% per year

Then the assumption there's no value in the batteries but you would have your cash

I've got 9.6 kWh batteries that cost 5.2k using about 8 kWh during peak and an EV so on Octopus go currently, I'll likely move to Intelligent Octopus next May

So for me:
RoI = ((40 - 4.5)*90%*8kWh*365*10)/5.2k = 1.79

Savings = 5.3k * (1+3.5%)^10 = 7.3k

EVandPV

goRt said:

I've got 9.6 kWh batteries that cost 5.2k using about 8 kWh during peak and an EV so on Octopus go currently, I'll likely move to Intelligent Octopus next May

You can actually switch tariffs with Octopus once a month, just in case you weren't aware.

goRt

EVandPV said:

goRt said:

I've got 9.6 kWh batteries that cost 5.2k using about 8 kWh during peak and an EV so on Octopus go currently, I'll likely move to Intelligent Octopus next May

You can actually switch tariffs with Octopus once a month, just in case you weren't aware.

Yes, but I'm one of the lucky ones who didn't get notified of the new rates so am on 4.5p for 3 hours starting at 20:30 until May next year - I'm happy to stick

EVandPV

I had a look at intelligent before renewing our Go.
The tariff is exactly the same as the current Go prices 7.5/40p and 6 hours at the cheap rate but the whole thing sounds a lot more involved with having to tell them how much charge you want every time you plug in an EV.
So we're just staying on Go for now.
We can pretty much charge the cars and storage batteries in the 4 hours anyway.

goRt

EVandPV said:

I had a look at intelligent before renewing our Go.
The tariff is exactly the same as the current Go prices 7.5/40p and 6 hours at the cheap rate but the whole thing sounds a lot more involved with having to tell them how much charge you want every time you plug in an EV.
So we're just staying on Go for now.
We can pretty much charge the cars and storage batteries in the 4 hours anyway.

You only have to do one "smart" charge per month, so you can disable that and just use the 6 hours every day outside of that

Petriix

Here's why I didn't get batteries:

With 6 months of smart meter combined with solar generation and grid export data I was able to model what my optimal savings would have been with an infinite sized battery. It turns out that I'd have only been able to save £20 per month on average.

Ultimately, since moving to Octopus Go, our peak usage is only ~ 20% of our total. Broadly speaking we use:

5000kWh per year total; of which
1000kWh comes free* from solar
1000kWh is peak rate at 24.25p
3000kWh is off peak at 5p

That's ~ £392.50 (plus standing charge) at an average of under 10p per unit.

At current Go rates it would increase to £625 at 15.625p per kWh.

Optimistically I could save £400 per year at these higher rates, if they stay high. I could have had an 8.2kWh Givenergy battery for about £4k this summer. It's more like £6k for a 9.6kWh now.

So roughly a 15 year ROI before making any savings. On the other hand, overpaying my mortgage by £6k will save me about £4k in interest (on top of the capital repayment).

While the headline cost of 5000kWh is £1700 at the new price guarantee, the reality is quite different for many people. You obviously need to do your own sums. 

chamelion

EVandPV said:

I had a look at intelligent before renewing our Go.
The tariff is exactly the same as the current Go prices 7.5/40p and 6 hours at the cheap rate but the whole thing sounds a lot more involved with having to tell them how much charge you want every time you plug in an EV.
So we're just staying on Go for now.
We can pretty much charge the cars and storage batteries in the 4 hours anyway.

It's not as complex as it sounds. Assuming you have a compatible car or charger with the intelligent option, all you do is plug in the car, which you'd do anyway. The platform does the rest. Worth noting that you do very frequently get additional slots of cheap electricity - the 6 hours is the absolute minimum, I regularly get at least an hour more. 

To me, assuming your car or charger is compatible, it's a no brainer over go - and something I'd even recommend you to switch to if rates haven't changed over go.

chamelion

Petriix said:

Here's why I didn't get batteries:

With 6 months of smart meter combined with solar generation and grid export data I was able to model what my optimal savings would have been with an infinite sized battery. It turns out that I'd have only been able to save £20 per month on average.

Ultimately, since moving to Octopus Go, our peak usage is only ~ 20% of our total. Broadly speaking we use:

5000kWh per year total; of which
1000kWh comes free* from solar
1000kWh is peak rate at 24.25p
3000kWh is off peak at 5p

That's ~ £392.50 (plus standing charge) at an average of under 10p per unit.

At current Go rates it would increase to £625 at 15.625p per kWh.

Optimistically I could save £400 per year at these higher rates, if they stay high. I could have had an 8.2kWh Givenergy battery for about £4k this summer. It's more like £6k for a 9.6kWh now.

So roughly a 15 year ROI before making any savings. On the other hand, overpaying my mortgage by £6k will save me about £4k in interest (on top of the capital repayment).

While the headline cost of 5000kWh is £1700 at the new price guarantee, the reality is quite different for many people. You obviously need to do your own sums. 

It boils down to a few things - your upfront cost, the delta between high and low, if you have solar, what type of payment you receive for solar (i.e deemed? Agile outgoing? Fit?), and ultimately your usage and usage profile. My newly purchased 2x us3000c last year have an roi of just over 2 years in my situation.