Battery Only SEG
Discussion
Just had a massive 16kWh Fogstar battery put in.
I’m doing 'battery-only' because my roof is 3 storeys high and faces the wrong way for solar and was very expensive. I’m currently on E.ON Next Drive (7p off-peak), but they won't let me claim SEG on my evening export because I don't have panels. I’ve heard Octopus or British Gas might be more flexible with battery-only exports. Has anyone successfully set this up? Any advice on which tariff actually pays out for grid-charged discharge?"
I’m doing 'battery-only' because my roof is 3 storeys high and faces the wrong way for solar and was very expensive. I’m currently on E.ON Next Drive (7p off-peak), but they won't let me claim SEG on my evening export because I don't have panels. I’ve heard Octopus or British Gas might be more flexible with battery-only exports. Has anyone successfully set this up? Any advice on which tariff actually pays out for grid-charged discharge?"
Sorry can't help, but I would like to know more about your system and installation. I was looking at Fogstar battery you have. It is all new to me, so I know little about how to choose inverter, battery and what is involved in installation. Do tell please!
We have an EV, are on Octopus IG, and like you, dont feel that solar is right for us. The better prospect is charging a home battery overnight and draining it during the day. Crazy when it comes to green efficiency but looks like it may make economic sense.
We have an EV, are on Octopus IG, and like you, dont feel that solar is right for us. The better prospect is charging a home battery overnight and draining it during the day. Crazy when it comes to green efficiency but looks like it may make economic sense.
Does buying electricity at 7p, then selling it back, make financial sense?
Remember there are charging and discharging losses, plus reduction in lifespan of the batteries, as well as the upfront cost of the equipment.
I sized our battery (no solar) to match the average daily use in the 5 months when the heatpump isn't used for heating, less the 6 hours when the rate is 7p.
Average daily use 14KWh, less 6 hours overnight at baseload of 400WH = approx 11.5KWh.
The battery should let us run entirely off-peak for 5 months of the year, excluding the electric shower "boost" from the grid.
Adding more capacity for the colder months, and selling the surplus in the summer, didn't seem to make financial sense. Happy to be proved wrong though.
Remember there are charging and discharging losses, plus reduction in lifespan of the batteries, as well as the upfront cost of the equipment.
I sized our battery (no solar) to match the average daily use in the 5 months when the heatpump isn't used for heating, less the 6 hours when the rate is 7p.
Average daily use 14KWh, less 6 hours overnight at baseload of 400WH = approx 11.5KWh.
The battery should let us run entirely off-peak for 5 months of the year, excluding the electric shower "boost" from the grid.
Adding more capacity for the colder months, and selling the surplus in the summer, didn't seem to make financial sense. Happy to be proved wrong though.
TUS373 said:
Sorry can't help, but I would like to know more about your system and installation. I was looking at Fogstar battery you have. It is all new to me, so I know little about how to choose inverter, battery and what is involved in installation. Do tell please!
We have an EV, are on Octopus IG, and like you, dont feel that solar is right for us. The better prospect is charging a home battery overnight and draining it during the day. Crazy when it comes to green efficiency but looks like it may make economic sense.
I found my installer Always Offline through the Fogstar website, highly recommend them. We have an EV, are on Octopus IG, and like you, dont feel that solar is right for us. The better prospect is charging a home battery overnight and draining it during the day. Crazy when it comes to green efficiency but looks like it may make economic sense.
SEG/Feed in tariff is supposed to be for regenerables only, hence the issue with EON not taking me. Ocotpus and British Gas don't care and I am currently applying to Octopus for a 4.1p feed in tariff, when I get it I will move to Octopus Go. When I am with Octopus the feed in tariff is 15p.
My plan is to install my own solar on the shed and in the garden, I can get close to the 8k the inverter will take but half of that is split west and east. I have a small 1k array at the moment running through an Ecoflow Stream, on a 3 pin plug.
The whole thing was £4300 installed. We seem to be using 6kwh a day so I have plenty of headroom for running the hot tub. Whatever I have left goes into the electric car and means I have more justification for not buying a proper car charger which would cost £1k and sticking with the granny charger. When I have the feed in tariff installed it does make sense to sell this "brown" energy back to the grid. The inverter has an AI mode and Octopus Flux could make sense in the sunnier months when my solar is going full blast.
The Fogstar goes down to 5% discharge and has a heater. There is a 32kwh battery as well, but I think there is a stock issue.
These 16kwh batteries have a 10 year warranty over 20,000 cycles which is plenty.
The battery keeps going offline at the moment, the installer is trying to work out if it is the battery or the inverter, very annoying.
lost in espace said:
I found my installer Always Offline through the Fogstar website, highly recommend them.
SEG/Feed in tariff is supposed to be for regenerables only, hence the issue with EON not taking me. Ocotpus and British Gas don't care and I am currently applying to Octopus for a 4.1p feed in tariff, when I get it I will move to Octopus Go. When I am with Octopus the feed in tariff is 15p.
My plan is to install my own solar on the shed and in the garden, I can get close to the 8k the inverter will take but half of that is split west and east. I have a small 1k array at the moment running through an Ecoflow Stream, on a 3 pin plug.
The whole thing was £4300 installed. We seem to be using 6kwh a day so I have plenty of headroom for running the hot tub. Whatever I have left goes into the electric car and means I have more justification for not buying a proper car charger which would cost £1k and sticking with the granny charger. When I have the feed in tariff installed it does make sense to sell this "brown" energy back to the grid. The inverter has an AI mode and Octopus Flux could make sense in the sunnier months when my solar is going full blast.
The Fogstar goes down to 5% discharge and has a heater. There is a 32kwh battery as well, but I think there is a stock issue.
These 16kwh batteries have a 10 year warranty over 20,000 cycles which is plenty.
The battery keeps going offline at the moment, the installer is trying to work out if it is the battery or the inverter, very annoying.
Thank you.That is really interesting and I appreciate it. Just looking at our usage on the Octopus app, we use just under 25kWh/day, and that is excluding the EV. Seems high to me - but that is what the app says. I thought a 16 kWh battery would do it - but think based on what I just checked, the even bigger battery would be better. That potentially pushed back my break even point. At £5 or 6/day, I might get the bill down to £1.50 day and save £3 or so - possibly £1000/year.SEG/Feed in tariff is supposed to be for regenerables only, hence the issue with EON not taking me. Ocotpus and British Gas don't care and I am currently applying to Octopus for a 4.1p feed in tariff, when I get it I will move to Octopus Go. When I am with Octopus the feed in tariff is 15p.
My plan is to install my own solar on the shed and in the garden, I can get close to the 8k the inverter will take but half of that is split west and east. I have a small 1k array at the moment running through an Ecoflow Stream, on a 3 pin plug.
The whole thing was £4300 installed. We seem to be using 6kwh a day so I have plenty of headroom for running the hot tub. Whatever I have left goes into the electric car and means I have more justification for not buying a proper car charger which would cost £1k and sticking with the granny charger. When I have the feed in tariff installed it does make sense to sell this "brown" energy back to the grid. The inverter has an AI mode and Octopus Flux could make sense in the sunnier months when my solar is going full blast.
The Fogstar goes down to 5% discharge and has a heater. There is a 32kwh battery as well, but I think there is a stock issue.
These 16kwh batteries have a 10 year warranty over 20,000 cycles which is plenty.
The battery keeps going offline at the moment, the installer is trying to work out if it is the battery or the inverter, very annoying.
I know nothing about inverters and solar is not top of the agenda. I assume that inverters are primarily designed for DC to battery, but a 'hybrid' inverter does AC to battery. I would like a system that behaves as a UPS too, given we do get power cuts from time to time. Again, from what have gleaned, an inverted should be <£750, but I do not know where to start!
We have a local renewables chap who might be able to install for me.I was budgeting £750 for that. Are those senisble numbers? Thanks!
A hybrid inverter allows you to have a battery and solar.
The sweet spot seems for me was the 16kwh and some solar to top up in the day. If I add another battery the cost is £2k and the payback is much longer approx 6 years.
My base load in the house is about 400w, you are way higher than that. I charge the car at night cheaply and the hot tub gets heated to 40 degrees then and acts as a thermal battery.
The sweet spot seems for me was the 16kwh and some solar to top up in the day. If I add another battery the cost is £2k and the payback is much longer approx 6 years.
My base load in the house is about 400w, you are way higher than that. I charge the car at night cheaply and the hot tub gets heated to 40 degrees then and acts as a thermal battery.
Although I have solar panels, the battery is the most useful thing and makes the most financial payback. Indeed if you assume a battery first, then modelling the payback on solar does not add up because you are only generating solar to relace 7p electricity instead of ~30p electricity, hence solar maybe (for my house at least) jumps from the illustration of 8 years to 30 years - longer than the expected lifespan of the panels!
I have a GivEnergy All in One 13.5kw whish is a tidy unit and covers our house usage for the day. Although our average usage is a bit higher than this, by the time you load shift most stuff (washing machine, dishwasher, car charging, etc) to the 7p Octopus period, and you consider that your baseload for those 6 hours of 7p do not count on the battery then you do not need as much as you might think.
The battery payback is quite simple to calculate without the SEG. If you have a 13.5kW and you charge it every night at 7p and your full rate is 29.63p, with a battery charge and discharge efficiency of 93%, and you use the full battery each day, then you are saving £2.96 per day, as around £1k per year.
The SEG at 15p allows you to sell back what you don't use. So that means it becomes safe to over-spec the battery. While the SEG technically is for renewable generated electricity only, I have found that Octopus do not have any checks, so my unused that I dump back at 11pm gets 15p credit. I have also experimented with cycling the battery during the night, so a full charge from 11:30pm, then a full discharge and then a full change back up, meaning 2x charges at 7p and 1x export at 15p, thus a 'free' charged battery by the morning. This worked and I was credited accordingly, however I only did it for a week so not sure if they'd come at me if I did it forever.
The lifespan of the batteries are quite good now, so they can take a lot of cycling. I think I have a 12 year unlimited cycles warranty, so given the battery payback is around 6 years then it works out quite well.
I have a GivEnergy All in One 13.5kw whish is a tidy unit and covers our house usage for the day. Although our average usage is a bit higher than this, by the time you load shift most stuff (washing machine, dishwasher, car charging, etc) to the 7p Octopus period, and you consider that your baseload for those 6 hours of 7p do not count on the battery then you do not need as much as you might think.
The battery payback is quite simple to calculate without the SEG. If you have a 13.5kW and you charge it every night at 7p and your full rate is 29.63p, with a battery charge and discharge efficiency of 93%, and you use the full battery each day, then you are saving £2.96 per day, as around £1k per year.
The SEG at 15p allows you to sell back what you don't use. So that means it becomes safe to over-spec the battery. While the SEG technically is for renewable generated electricity only, I have found that Octopus do not have any checks, so my unused that I dump back at 11pm gets 15p credit. I have also experimented with cycling the battery during the night, so a full charge from 11:30pm, then a full discharge and then a full change back up, meaning 2x charges at 7p and 1x export at 15p, thus a 'free' charged battery by the morning. This worked and I was credited accordingly, however I only did it for a week so not sure if they'd come at me if I did it forever.
The lifespan of the batteries are quite good now, so they can take a lot of cycling. I think I have a 12 year unlimited cycles warranty, so given the battery payback is around 6 years then it works out quite well.
That is very interesting eein, I hadn't thought of cycling the battery during the import period. Octopus approved my SEG this morning.
Solis have admitted there is a software error now it is very frustrating to have a battery and not being able to use it. The luxury of using electricity at approx 8p a unit cannot be underestimated.
Solis have admitted there is a software error now it is very frustrating to have a battery and not being able to use it. The luxury of using electricity at approx 8p a unit cannot be underestimated.
Your ability to cycle in the night tariff will likely be limited by the size of inverter you have.
Similarly your house consumption from the battery may be limited by the inverter. I have ~6kW inverter so my 10kW electric shower runs on a mix of battery and grid.
Even just charging at night and using through the day I've got my average price of grid electric consumption down to 7.15p - you see this on your Octopus bill.
Similarly your house consumption from the battery may be limited by the inverter. I have ~6kW inverter so my 10kW electric shower runs on a mix of battery and grid.
Even just charging at night and using through the day I've got my average price of grid electric consumption down to 7.15p - you see this on your Octopus bill.
Interesting re the inverter size. Lots of things to think about.
We have an EV are on Octopus Intelligent Go. I know their terms have or are changing but no sure how. I assume I can still plug in my car during the day on an opportunistic basis, and if the grid allows we get a charge at 7p instead of about 28p per kWh. The load is 7kWh.
If we had a battery and an inverter (but no solar), and say it was fully charged and daytime...and then plug in the car, how is the load all balanced out? Does the EV take it all from the grid, or part from grid and battery (losing our 7p charged up battery for 7p charging the car up).
Can't get my head around it. Thanks.
We have an EV are on Octopus Intelligent Go. I know their terms have or are changing but no sure how. I assume I can still plug in my car during the day on an opportunistic basis, and if the grid allows we get a charge at 7p instead of about 28p per kWh. The load is 7kWh.
If we had a battery and an inverter (but no solar), and say it was fully charged and daytime...and then plug in the car, how is the load all balanced out? Does the EV take it all from the grid, or part from grid and battery (losing our 7p charged up battery for 7p charging the car up).
Can't get my head around it. Thanks.
lost in espace said:
Solis have admitted there is a software error now it is very frustrating to have a battery and not being able to use it. The luxury of using electricity at approx 8p a unit cannot be underestimated.
Hope you get resolved soon.
TUS373 said:
Interesting re the inverter size. Lots of things to think about.
We have an EV are on Octopus Intelligent Go. I know their terms have or are changing but no sure how. I assume I can still plug in my car during the day on an opportunistic basis, and if the grid allows we get a charge at 7p instead of about 28p per kWh. The load is 7kWh.
If we had a battery and an inverter (but no solar), and say it was fully charged and daytime...and then plug in the car, how is the load all balanced out? Does the EV take it all from the grid, or part from grid and battery (losing our 7p charged up battery for 7p charging the car up).
Can't get my head around it. Thanks.
You just need software to tell your inverter to switch to charging mode whenever the Octopus rate drops to off-peak.We have an EV are on Octopus Intelligent Go. I know their terms have or are changing but no sure how. I assume I can still plug in my car during the day on an opportunistic basis, and if the grid allows we get a charge at 7p instead of about 28p per kWh. The load is 7kWh.
If we had a battery and an inverter (but no solar), and say it was fully charged and daytime...and then plug in the car, how is the load all balanced out? Does the EV take it all from the grid, or part from grid and battery (losing our 7p charged up battery for 7p charging the car up).
Can't get my head around it. Thanks.
Stops the car draining the house battery, and tops the battery up at 7p in the "bonus" slots.
I use Home Assistant, but I think there are simpler solutions out there.
Looks like the taxman may want his share of any profits: https://www.youtube.com/watch?v=IEY2ha_TYCI
superpp said:
I asked my installer about the Fogstar units and he contacted Solis to ask them about their support. They told us they don't support Fogstar and wouldn't offer any help fault finding should there be a problem. I didn't proceed.
Hope you get resolved soon.
My installer has been talking to Solis, this morning they admitted the fault is with the inverter. It communicates using a Pylon protocol I am sure any Pylon compatible battery would be OK. If you email go@alwaysoffpeak.co.uk and speak to Ric he is very knowledgeable. Hope you get resolved soon.
nyt said:
Looks like the taxman may want his share of any profits: https://www.youtube.com/watch?v=IEY2ha_TYCI
You are correct, I also have a stake in a solar farm and they want a cut of that too.TUS373 said:
Interesting re the inverter size. Lots of things to think about.
We have an EV are on Octopus Intelligent Go. I know their terms have or are changing but no sure how. I assume I can still plug in my car during the day on an opportunistic basis, and if the grid allows we get a charge at 7p instead of about 28p per kWh. The load is 7kWh.
If we had a battery and an inverter (but no solar), and say it was fully charged and daytime...and then plug in the car, how is the load all balanced out? Does the EV take it all from the grid, or part from grid and battery (losing our 7p charged up battery for 7p charging the car up).
Can't get my head around it. Thanks.
The control to ensure your car charges from the grid and does not drain your battery is system specific - some have a control for this and some do not. It is also not possible in most systems to say draw from the grid to charge the car but keep the battery supplying the house. The source can only be one source to it's max and then top up from another method.We have an EV are on Octopus Intelligent Go. I know their terms have or are changing but no sure how. I assume I can still plug in my car during the day on an opportunistic basis, and if the grid allows we get a charge at 7p instead of about 28p per kWh. The load is 7kWh.
If we had a battery and an inverter (but no solar), and say it was fully charged and daytime...and then plug in the car, how is the load all balanced out? Does the EV take it all from the grid, or part from grid and battery (losing our 7p charged up battery for 7p charging the car up).
Can't get my head around it. Thanks.
The recently updated Octopus intelligent Go scheme has something about charging during the day at 7p, but they have introduced a limit to this. It was all a bit too complicated and I have found the system is slow to 'intelligent' configure and before it does that it charges the car at full rate for a few mins.
eein said:
The control to ensure your car charges from the grid and does not drain your battery is system specific - some have a control for this and some do not. It is also not possible in most systems to say draw from the grid to charge the car but keep the battery supplying the house. The source can only be one source to it's max and then top up from another method.
The recently updated Octopus intelligent Go scheme has something about charging during the day at 7p, but they have introduced a limit to this. It was all a bit too complicated and I have found the system is slow to 'intelligent' configure and before it does that it charges the car at full rate for a few mins.
Thanks. So if I understand correctly, when an EV charges, the home battery should be set to charge at the same time. On OIG that means 11.30pm to 05.30am, 6 hours out of 24.The recently updated Octopus intelligent Go scheme has something about charging during the day at 7p, but they have introduced a limit to this. It was all a bit too complicated and I have found the system is slow to 'intelligent' configure and before it does that it charges the car at full rate for a few mins.
Im not sure what happens now when plugging in the EV during the day. I don't precisely know OIG's new rules. I thought it was 7p whenever it is under their control. But saying that, it sounds difficult to configure the home battery to sync its operation with random EV charging times.
Steep learning curve here.
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