Home batteries *Can* save you money

QrizB

Solarchaser said:

I've edited this thread title to something more accurate

I quite liked your original title, it was a little bit provocative

Thank you for the update, it's good to see how domestic time-shifting of energy supply works in practice.

Solarchaser

JKenH said:

Solarchaser said:

For March 16th 2021 to March 15th 2022 I used 3689kwh from my smart meter confirmed by the bills.
I have paid £318 for this.
£86.9 was standing charge, so £231.1 in electricity 
Average price of 6.26p (rate of 14.2 and 4.5p/kwh)

Batteries have discharged a total of 4093kwh

I've exported 2084kwh excess solar in this time
A total of 7139kwh of solar was generated, (had some issues, should have been more like 7500) and so generated minus exported equals 5055kwh used, plus the 3689 bought brings the total usage up to 8744kwh

Arguably some of that wasted in round trip of the inverter, say 20% of the 4093 would bring it to 3274, or another way of saying it would be that I used 818kwh less than I would if I didn't have batteries.
So without batteries my consumption would be more like 7926kwh.

Using that all at 14.2ppkwh would cost £1125.49 I've paid £318 a saving you could say of £807.49 so for me around an 11 year payback.
At the more recent prices of 30ppkwh it would be £2377.8
Assuming my cost would roughly double as well, as that's going to happen at the end of my fixed term then the difference would be £1741.8 and around a 5 year payback.

I've deliberately been conservative with this, adding in the daily charge to correct price, but not adding it to future as I'd rather be on the side of caution rather than being some sort of salesman selling solar, as we all have seen.

So anyway my point is, without the recent price increase, solar definitely makes sense, with the recent price increases, if you are a fairly high user of electricity... and as we shift away from fossils, we are all going to be.. then solar plus batteries makes sense, though I'll caveat that by saying I still dont think the tesla offering does.

Hi @Solarchaser just a small point. Presumably, without a battery, some of your usage would be at the cheaper Go Faster rate. I have solar but don’t have a battery so shift what usage I can to the cheaper rate (including my car charging) so my average rate on Go Faster works at around 9p/kWh plus VAT so say 9.5p. I realise you have a different use profile but I imagine if you didn’t have a battery you could perhaps move more of your use (or perhaps just your car charging into that cheap rate window so you could use your solar to cover household usage). 

Hi Ken, yeah that's a fair point.
I was trying to think of all angles, but definitely missed this one 👍

Solarchaser

QrizB said:

Solarchaser said:

I've edited this thread title to something more accurate

I quite liked your original title, it was a little bit provocative

Thank you for the update, it's good to see how domestic time-shifting of energy supply works in practice.

Haha, It amused me at the time, but when I looked at it today I thought it a bit devisive and may upset our right leaning friends.

JKenH

Solarchaser said:

JKenH said:

Solarchaser said:

For March 16th 2021 to March 15th 2022 I used 3689kwh from my smart meter confirmed by the bills.
I have paid £318 for this.
£86.9 was standing charge, so £231.1 in electricity 
Average price of 6.26p (rate of 14.2 and 4.5p/kwh)

Batteries have discharged a total of 4093kwh

I've exported 2084kwh excess solar in this time
A total of 7139kwh of solar was generated, (had some issues, should have been more like 7500) and so generated minus exported equals 5055kwh used, plus the 3689 bought brings the total usage up to 8744kwh

Arguably some of that wasted in round trip of the inverter, say 20% of the 4093 would bring it to 3274, or another way of saying it would be that I used 818kwh less than I would if I didn't have batteries.
So without batteries my consumption would be more like 7926kwh.

Using that all at 14.2ppkwh would cost £1125.49 I've paid £318 a saving you could say of £807.49 so for me around an 11 year payback.
At the more recent prices of 30ppkwh it would be £2377.8
Assuming my cost would roughly double as well, as that's going to happen at the end of my fixed term then the difference would be £1741.8 and around a 5 year payback.

I've deliberately been conservative with this, adding in the daily charge to correct price, but not adding it to future as I'd rather be on the side of caution rather than being some sort of salesman selling solar, as we all have seen.

So anyway my point is, without the recent price increase, solar definitely makes sense, with the recent price increases, if you are a fairly high user of electricity... and as we shift away from fossils, we are all going to be.. then solar plus batteries makes sense, though I'll caveat that by saying I still dont think the tesla offering does.

Hi @Solarchaser just a small point. Presumably, without a battery, some of your usage would be at the cheaper Go Faster rate. I have solar but don’t have a battery so shift what usage I can to the cheaper rate (including my car charging) so my average rate on Go Faster works at around 9p/kWh plus VAT so say 9.5p. I realise you have a different use profile but I imagine if you didn’t have a battery you could perhaps move more of your use (or perhaps just your car charging into that cheap rate window so you could use your solar to cover household usage). 

Hi Ken, yeah that's a fair point.
I was trying to think of all angles, but definitely missed this one 👍

While you were replying to me (thanks btw) I was also adding an edit to my post.

Solarchaser

JKenH said:

Solarchaser said:

JKenH said:

Solarchaser said:

For March 16th 2021 to March 15th 2022 I used 3689kwh from my smart meter confirmed by the bills.
I have paid £318 for this.
£86.9 was standing charge, so £231.1 in electricity 
Average price of 6.26p (rate of 14.2 and 4.5p/kwh)

Batteries have discharged a total of 4093kwh

I've exported 2084kwh excess solar in this time
A total of 7139kwh of solar was generated, (had some issues, should have been more like 7500) and so generated minus exported equals 5055kwh used, plus the 3689 bought brings the total usage up to 8744kwh

Arguably some of that wasted in round trip of the inverter, say 20% of the 4093 would bring it to 3274, or another way of saying it would be that I used 818kwh less than I would if I didn't have batteries.
So without batteries my consumption would be more like 7926kwh.

Using that all at 14.2ppkwh would cost £1125.49 I've paid £318 a saving you could say of £807.49 so for me around an 11 year payback.
At the more recent prices of 30ppkwh it would be £2377.8
Assuming my cost would roughly double as well, as that's going to happen at the end of my fixed term then the difference would be £1741.8 and around a 5 year payback.

I've deliberately been conservative with this, adding in the daily charge to correct price, but not adding it to future as I'd rather be on the side of caution rather than being some sort of salesman selling solar, as we all have seen.

So anyway my point is, without the recent price increase, solar definitely makes sense, with the recent price increases, if you are a fairly high user of electricity... and as we shift away from fossils, we are all going to be.. then solar plus batteries makes sense, though I'll caveat that by saying I still dont think the tesla offering does.

Hi @Solarchaser just a small point. Presumably, without a battery, some of your usage would be at the cheaper Go Faster rate. I have solar but don’t have a battery so shift what usage I can to the cheaper rate (including my car charging) so my average rate on Go Faster works at around 9p/kWh plus VAT so say 9.5p. I realise you have a different use profile but I imagine if you didn’t have a battery you could perhaps move more of your use (or perhaps just your car charging into that cheap rate window so you could use your solar to cover household usage). 

Hi Ken, yeah that's a fair point.
I was trying to think of all angles, but definitely missed this one 👍

While you were replying to me (thanks btw) I was also adding an edit to my post.

Hi Ken, thanks, good points again.
Yes I am comfortable with electrics and installed it all myself as well as buying the constituent parts when they were cheaper or second hand at times, and reusing other materials (my second set of solar panels were mounted using old decking boards) the difference imo is maybe £500-1000 so say roughly another year of payback, so 12 years, or taking things to the extreme say 15 years at the "old" prices if it was all professionally done.

It's worth noting too that the prices of batteries have actually increased in the last few years which is not the trend we all thought was likely.
I was able to get new pylons for £725 and they are over £800 these days I think, and everyone knows about them too, so much harder to get a cheap second hand one.

I didn't include the fit from the main system because I'm exporting as much now as I always did, perhaps more, so I've essentially *forgot* my initial solar system and based my calculations on building the second array and having the batteries charging from it, which isn't 100% true, but close enough to reality to be passable I think.
I was also thinking that those looking into batteries now are less likely to have fit based solar already (perhaps I'm wrong).

Trying to find that middle ground between saying what's possible and providing figures without saying "only if you do exactly what I've done, you will get this".

Solarchaser

I think it's also worth saying that if I was going for return on investment as my primary goal, I'd have bought less inverters and less batteries.
I have 9 batteries in total giving around 20kwh of storage, for just under half of the year the batteries don't fully drain overnight.
I also have 2 inverters running in parallel and the times where more than 1 inverter is needed is pretty low, likely less than 10%, maybe even 5% so this is definitely a *waste* of money if going for roi and therefore it's possible to make around the same savings as I have made by spending less.

How much less depends on you and your home.
As has been established with the figures above I'm a high user with over 7mwh/ year.
In the summer months it's unusual for me to see the charge level drop below 50% overnight, due to the longer daylight /solar which suggests that something around maybe 12kwh would be best for roi for my household 
If you use significantly less. You will need significantly less too.

I felt this was worth mentioning along side the points Ken had brought up.

I spend around 9k for all of mine, but that includes the second set of panels and inverters, so say a little under 7k for the lux and batteries, id think buying officially and getting installed professionally it would come in at around 8k these days, but again that's with too much battery capacity for best roi.

Somewhere around 5k for 1 inverter and 5/6 batteries should still be doable with a little shopping around, a quick Google suggests £830 for a pylontech battery.
The lux I bought from think renewables was £750.
Think renewables also trade as big green beard, pv pro, gigabiz, homeswitch and a few other names.

So yeah I think you could make almost the same savings I've made by spending significantly less and getting it done professionally 

michaels

When you are comparing against 14.2p peak units, is it possible you could have fixed on a non tou tariff at say 11 to 12p per unit?

We are thinking batteries are a definite win with current tariffs but the unknowns are whether rates will stay this high or higher or fall back to historic normal levels and whether Octopus go style tariffs will always be available which makes it harder to commit to the investment.

Currently we are drawn to buying a second old Nissan leaf to use with the v2g unit as a v2h as we could then sell this on if tariffs go back down and the financials change.

Solarchaser

Yeah you are lucky with the v2g.
Due to me adding the second solar system they said I'd too much solar to be in the trial.

I seen on fully charged that a (Dutch?) Company has sorted v2g for ccs, so hoping that makes its way over here sometime soon.

When I picked up the 14.2 rate from octopus,  the only tarrif close to it without tou was edf with 16p, so the octopus tarrif was cheaper for me even without the cheaper rate. 

I haven't looked recently, but I know it all looks horrendous. 
I dont see the price of leccy coming down until mid England and south Wales uses less gas for making electricity, (not just mid England and south Wales, but specifically mid England uses a lot)and thats not a quick process.
Though it's nice to see a good wind contribution to west Midlands today.

The government suggestion of opening new fields is said to be a 10 years away thing, and the Russian aggression on poor Ukraine is sure to keep gas prices up too, so I don't see the prices coming down any time soon. In fact there's supposed to be further rises in October.

No one can say for sure about tou tarrifs, but my feeling is they will get more prevalent rather than less, turning down wind in the evenings /overnight doesn't make sense if you can sell it a bit cheaper.