Solar panels and battery storage

Smudger558

Active Member
Yeah I've seen that it's starting to sound like a no brainer I'm in process of getting quotes just thought you lovely people on our forums thought about it
 

Belzok

Distinguished Member
Yeah I've seen that it's starting to sound like a no brainer I'm in process of getting quotes just thought you lovely people on our forums thought about it
Friend of mine has just gone for the same system, Givenergy 8.2kWh with a standard 3kW inverter.

He's going through the commissioning now and it will be switched on in the next couple of days

As long as the difference between daytime and night time rates keeps above 10p ish it really does make sense as it has a short payback period.

Also like that its a British company that is offering a competitive option.

Might think about getting one, especially solar isn't much use for me with an EW roof, oh and you can move a battery if you move house, solar not so much. I'm also moving from a gas hob to induction so that will make payback even quicker.
 

ih8mondays

Active Member
Someone on MSE forums was critical of that video, in particular around you needing an electric vehicle to get onto Octopus Go.


If you plan to move house in the next ten years it won’t be worth having it installed, hopefully a good supplier will give you calculations as to how much it will save you, but payback could be 11+ years.

The batteries will probably need replacing around 10+ years too. Some will guarantee the batteries for 10 years, some for different periods of time.
 

Belzok

Distinguished Member
Someone on MSE forums was critical of that video, in particular around you needing an electric vehicle to get onto Octopus Go.


If you plan to move house in the next ten years it won’t be worth having it installed, hopefully a good supplier will give you calculations as to how much it will save you, but payback could be 11+ years.

The batteries will probably need replacing around 10+ years too. Some will guarantee the batteries for 10 years, some for different periods of time.
Yes very much depends on being on an economy 4, or 7, tarrif and your on-peak consumption, its just a simple calculation.

Only question is how long will on/off peaks tarrifs last with EVs charging overnight and levelling the demand curve, by the time it dies k fully expect there to be incentives for load leveling home batteries.

Installation cost will be dependent on how easy it is to get to your consumer unit or DB that has a decent enough supply, friend has it in his garage right next to the DB so the electrician only has to commission it. If I get one it would go right next to the board.

Givenergy offer a 10 year unlimited throughout warranty.
 

oneman

Well-known Member
I've done sums for a my system with is 4Kw and really it depends on your usage. I've got AC, couple of servers, 2 people living in the house during the day and TBH I use most of what I generate so not much would be going into batteries. Plus it would be a few of the year at best there is a surplus.
 

Belzok

Distinguished Member
I've done sums for a my system with is 4Kw and really it depends on your usage. I've got AC, couple of servers, 2 people living in the house during the day and TBH I use most of what I generate so not much would be going into batteries. Plus it would be a few of the year at best there is a surplus.
The earlier FIT deals in the UK paid on generation not the energy supplied to the grid I think.

It's all about the difference between your on and off peak rates and your export rate.

As you say it's just sums for your own use patterns will be worth it for some and not for others
 

ih8mondays

Active Member
Probably not worth getting the batteries if they won’t get used much.

Unless you can buy cheap overnight and use it the next day - not sure how time of use tariffs will look next year, hopefully gas and electric prices start to come down again…
 

ih8mondays

Active Member
The new scheme is SEG

If you are on that you can export electricity when the demand is high, to make money that way.

I think Octopus need you to be on agile incoming to get agile SEG export payments.

Not sure being on agile is the best place to be at the moment!!

If you can avoid using anything from the grid, maybe it would be okay, but 35p most of the day isn’t good if you need to buy electric!
 

oneman

Well-known Member
Probably not worth getting the batteries if they won’t get used much.

Unless you can buy cheap overnight and use it the next day - not sure how time of use tariffs will look next year, hopefully gas and electric prices start to come down again…
I was thinking about cheap overnight option, can't see a tariff cheap enough at the moment to make it worthwhile.
 

oneman

Well-known Member
The earlier FIT deals in the UK paid on generation not the energy supplied to the grid I think.

It's all about the difference between your on and off peak rates and your export rate.

As you say it's just sums for your own use patterns will be worth it for some and not for others
I'm on the old deal, they assume 50% of generation is fed back in. AFAIK you can't discharge batteries in daytime to boost that figure else you could charge overnight and feed it back in during the day.

What will be interesting when we start using EV cars as energy storage.
 

Belzok

Distinguished Member
I'm on the old deal, they assume 50% of generation is fed back in. AFAIK you can't discharge batteries in daytime to boost that figure else you could charge overnight and feed it back in during the day.

What will be interesting when we start using EV cars as energy storage.
Don't think you're allowed to change the setup for the solar, presumably this has the export meter bit.

The newer installs are simply get paid for export at a rate, very much depends if the difference between the export and off peak is enough yo justify doing that.

Main benefit will be for removing expensive consumption during the day.

You probably should look to see if you can move washing and drying loads to off peak along with dishwashers before looking at a battery, or at least consider that when doing the calculations.

The grid being able to use a couple of kWhs from a couple of million home batteries or cars would make a massive difference to our generation capacity requirements.

All fascinating stuff for me and shows and awful lot of the problems we have today with dirty generation around the world could be significantly mitigated fairly rapidly.
 

spinaltap

Distinguished Member
Solar and Storage Show at NEC next week (Tuesday to Thursday). Free admission. GivEnergy is one of the many exhibitors.
 

Basinguy

Active Member
The guy in the video makes some pretty wild assumptions with no evidence to back them up.

1) electricity prices will continue to rise forever more. Based on what exactly? The UK electricity prices are largely tied to the price of gas because that is the main source of fuel for electrical generation.
The price is currently high due to short supply and high demand, is that guaranteed to remain the case forever? Possibly but equally possibly not, no evidence points in either direction.

Also as we increase our wind power capacity (plus other renewables), that price will detach from gas and find its own market rate, the same way it has detached from coal over the past 2 decades and now follows gas. What will that new rate be for a generation method with no fuel consumption? Nobody knows.

He also assumes in his calculations that your house consumes 0 during the night period other than the battery. If you have an EV and can benefit from the better overnight tariff, moving things like dishwasher and tumble drier overnight can already shift a fair portion of your usage to the cheaper rate without the need for any batteries, potentially pushing that payback from 10 to more like 13 years, (also consider this is break even, you havent saved a penny at this point, especially if you fund your batteries with a loan in which case your payback is probably more like 15 years, likely longer than the life of the batteries).
Gas is still roughly equivalent to the night electric tarrifs so heating remains pointless (unless you live in an area with high gas prices or have electric heating anyway).

Also, as more and more people buy EVs and Batteries, and make use of cheaper overnight electricity, the load demand will level out and the incentives will drop.
I'm sure there will always be a small incentive for using electricity overnight rather than at peak times during the day, but it's pretty foolish to believe that is going to be the case when EVs become the majority.
peak UK demand averages at 42GW and minimum demand is about 25GW, that's a difference of 17GW between minimum and maximum.
17GW = 17,000MW = 17,000,000KW
17 million Kilowatts difference. If a standard EV charger is 7.2KW then it only takes 2.5million cars being charged for this cheaper overnight period to become the new peak time of usage, and the pricing model changes again.
there's are 33million cars in the UK so it only takes 1in13 cars to become EVs for this to become a reality.
 

Belzok

Distinguished Member
The guy in the video makes some pretty wild assumptions with no evidence to back them up.

1) electricity prices will continue to rise forever more. Based on what exactly? The UK electricity prices are largely tied to the price of gas because that is the main source of fuel for electrical generation.
The price is currently high due to short supply and high demand, is that guaranteed to remain the case forever? Possibly but equally possibly not, no evidence points in either direction.

Also as we increase our wind power capacity (plus other renewables), that price will detach from gas and find its own market rate, the same way it has detached from coal over the past 2 decades and now follows gas. What will that new rate be for a generation method with no fuel consumption? Nobody knows.

He also assumes in his calculations that your house consumes 0 during the night period other than the battery. If you have an EV and can benefit from the better overnight tariff, moving things like dishwasher and tumble drier overnight can already shift a fair portion of your usage to the cheaper rate without the need for any batteries, potentially pushing that payback from 10 to more like 13 years, (also consider this is break even, you havent saved a penny at this point, especially if you fund your batteries with a loan in which case your payback is probably more like 15 years, likely longer than the life of the batteries).
Gas is still roughly equivalent to the night electric tarrifs so heating remains pointless (unless you live in an area with high gas prices or have electric heating anyway).

Also, as more and more people buy EVs and Batteries, and make use of cheaper overnight electricity, the load demand will level out and the incentives will drop.
I'm sure there will always be a small incentive for using electricity overnight rather than at peak times during the day, but it's pretty foolish to believe that is going to be the case when EVs become the majority.
peak UK demand averages at 42GW and minimum demand is about 25GW, that's a difference of 17GW between minimum and maximum.
17GW = 17,000MW = 17,000,000KW
17 million Kilowatts difference. If a standard EV charger is 7.2KW then it only takes 2.5million cars being charged for this cheaper overnight period to become the new peak time of usage, and the pricing model changes again.
there's are 33million cars in the UK so it only takes 1in13 cars to become EVs for this to become a reality.
I think in the short term he's probably right, especially with Russia playing games, but long term who knows.

EVs will flatten the demand curve over the next 10 years.

I do wonder if consumers will get paid for opening up our batteries for utilities control to add load balancing without a massive capital investment from them.

It's all supposition though.
 

stblob

Well-known Member
I guess going of grid today is could easy enough. How many 500watts solar panels would you need and how big a battery wall would be required?
 

ih8mondays

Active Member
GivEnergy batteries can be hooked into Octopus Agile via an API key - so they can charge when the daily rates are the lowest.

So can’t see why they wouldn’t be able to automatically export at times of high demand. You’d probably want people to opt into that and pay them accordingly of course, not just mandate it!
 

Basinguy

Active Member
Looking at the gas price over the last year you can see already that the hype is already easing quite considerably.

Trading rates for UK electricity are currently 19p.
Next month and quarter are 27p. Next year is 12p.
You can see that the peak price for electricity is about to come in the next month's.
The future price for next year shows the anticipation that prices will drop back down.

While the Octopus tarrif is great for EVs right now, and moving as much load as you can overnight will save you additional £ (exactly what I will be doing when mine arrives). Spending that amount on a battery system on a hunch that a donnie on YouTube might be right (when actual market evidence shows he is not) is a bit careless.
 

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The Dreamer

Distinguished Member
We’re just about to add some more solar, and a Tesla Powerwall to our system.

Not cheap, at just under £17K, but it should enable us to join the Tesla tariff (operated by Octopus), which has a current rate of 11p/KWh for both usage and export.

This means we should be overproducing during the summer months, which will subsidise our winter usage. That’s the plan anyway. In total we’ll have a 9KW solar system.

The only real downside of the tariff, that I can see, is that Octopus control the Powerwall remotely, rather than you having control over battery usage, as your system becomes just another part of the ‘Tesla grid’.

Anyone else considering similar? I believe @gangzoom has a powerwall, though not sure he’s on the Tesla tariff.
 

Chester

Well-known Member
I've just placed a deposit for a Powerwall 2 and Gateway. We already have 4kW of solar into a 3.6kW inverter. Even though I work from home, the energy consumption I normally require doesn't add much to our ~150W base load, probably <100W. Obviously this spikes with kitchen use! The amount we export really does depend on the weather. We had an atrocious August this year due to cloud cover, and I doubt solar output would have kept a battery charged for night time use on some of the bad days. I know in winter the solar output can regularly dip below 1kWh/day, but then again with beautiful blue sunny skies in freezing cold January this year, we managed to fully charge our small EV over 2 days on solar alone!

We have just started to experiment with electric heating and with a recent bathroom rip out, complete redesign and fit, we've gone with electric under-floor heating. It's load is ~250W during demand and typically <2kWh used on a cold day. The Powerwall is going to play an important part of keeping our energy costs down. We're on Octopus Go, and the hope is that we can intelligently charge the battery overnight depending on the following day's forecast. I have no idea how realistic this is.

I initially wanted a DC coupled battery into a hybrid inverter with the idea of reducing box count and a simpler system, at least in theory. I've been reliably informed by the electricians that this will most likely lead to discharging the home battery as we're also EV owners. I've been convinced to use an AC coupled system instead, and the addition of the Gateway gives us the ability to continue with <=5kW loads during a power cut. It's not normally a problem around here, but better to be prepared especially WFH.

I believe our usage should provide ROI within a 5-6 year period, plus knowing we're not placing demands on the grid at peak times and helping to bring balance. If the experiment works, we're likely to pursue a change to electric water heating and then possibly electrically heating the whole home, in which case 4kW solar is nowhere near enough. However we're treading water with this and progressing gradually so we can take our time and learn from our experience, and share it too. So far solar alone is working well; we just wish for those beautiful blue and sunny skies!
 

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