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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
RedMod3
Member
Bought at 0% VAT, and bought for the business case of significantly cutting energy costs over the next 7 years.
If Octopus Flex had an option to be given 12 IO style flux rate slots overnight rather then the fixed 3hr Flex time, (controlled with same APIs as Octopus IO) then many of of our concerns would be removed. This would also allow better use of wind power.
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Looking at flux pricing in more details.
If you have a 9kwh battery with a max 3kw charge/discharge rate then you get the best results from charing to 100% in the 3hr flux rate and a forced discharged at 3kw over the 3hr peak rate. (With no discharge allowed at other times.)
As all export rates other then in the 3hr flex slot is higher then then flex import rate you can never lose out by putting too much charged in within the flex slot and then having to export PV.
As the peak export rate is higher then all none peak import rates, you can never lose out by emptying the battery in the last minute of peak.
The battery should not provide any power to home when it is does not have enough charge to discharge at full inverter capacity in Peak Rate. So for example a 20kwh battery on a dedicated 5kw inverter should always save 15kwh of charge for peak time. (Then track load after peak time.)
We now need battery systems that can fully charge in 3hr hours, few other countries have that requirement. But for example on a 5kw charge/discharged I would like 20kwh (18kwh usable) of batteries with PV so I can put the kettle on even when PV output is under 3kw without importing.
Clearly heat hot water between 2am-5am, no point having PV diverters as flex import is lower then day export. Along with turning the heatpump off between 4pm to 7pm unless export limited.
______
Looking at flux pricing in more details.
If you have a 9kwh battery with a max 3kw charge/discharge rate then you get the best results from charing to 100% in the 3hr flux rate and a forced discharged at 3kw over the 3hr peak rate. (With no discharge allowed at other times.)
As all export rates other then in the 3hr flex slot is higher then then flex import rate you can never lose out by putting too much charged in within the flex slot and then having to export PV.
As the peak export rate is higher then all none peak import rates, you can never lose out by emptying the battery in the last minute of peak.
The battery should not provide any power to home when it is does not have enough charge to discharge at full inverter capacity in Peak Rate. So for example a 20kwh battery on a dedicated 5kw inverter should always save 15kwh of charge for peak time. (Then track load after peak time.)
We now need battery systems that can fully charge in 3hr hours, few other countries have that requirement. But for example on a 5kw charge/discharged I would like 20kwh (18kwh usable) of batteries with PV so I can put the kettle on even when PV output is under 3kw without importing.
Clearly heat hot water between 2am-5am, no point having PV diverters as flex import is lower then day export. Along with turning the heatpump off between 4pm to 7pm unless export limited.
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I asked Greg Jackson on Twitter if IO could be applied to Tesla Powerwall, so it charged at the same time as the car charge windows. He said it could but the PowerWall API is not available to them. Could see that being useful if for example it was a dull day and battery needed a charge and Octopus had set a charge window during the day
Would be much better for Tesla to use the Octopus IO API as it would result in simpler software.
ACarneiro
Active Member
According to folks automating this using HA, the slots assigned outside the set period are only billed at the lower price if your car is charged in that period, and you can't determine this from the Octopus API. Makes it a complex automation.
Octopus Energy - Intelligent Tariff
In my experience it has been 100% reliable since I started using it a few months ago… always matching my intelligent slots, no matter when they are (early evening, overnight, extended mornings etc), allowing my car and home battery to charge whenever the slots are made. However, if you are...
community.home-assistant.io
I’m pretty sure all tariffs are flexible now for Octopus. My fixed IO ends next week. At which point off peak goes up to 10p per kWh. Ive had a 6.7kw PV array for just under a year and PW2 since December. Running some rough calculations I think I could save between £30-80 per month May to Sep on the Flux plan. So I think I’m going to switch in May and then switch back to IO in Oct. The one annoying thing is not being able to tell a PW to discharge or even stop diverting solar at the peak time. There is the option looking towards the end of this thread PW discharge but only in the US and appears to only be on Powerwall +.
Has any one found a way to stop the PW from charging or force it to discharge?
Just looking at my DNO application, the battery export is 0kw. Has anyone or does anyone know if you can apply for battery export, and if so can you then get the PW reconfigured to export to grid?
Has any one found a way to stop the PW from charging or force it to discharge?
Just looking at my DNO application, the battery export is 0kw. Has anyone or does anyone know if you can apply for battery export, and if so can you then get the PW reconfigured to export to grid?
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ACarneiro
Active Member
I think that if you input all your tariff data into your Gateway setup the system may well decide to when to stop charging the Powerwall.
I saw a similar behaviour when I had a Power Hour in the middle of day day: I added that hour to the tariff and the Gateway exported all the solar production of the morning to the grid despite the Powerwalls not being full and then filled the Powerwalls with free grid electricity. It seems there is a little bit of AI going on.
How long did you leave it after making the change? I’ve tried testing it and left it for a while today and nothing changed.
ACarneiro
Active Member
I don't remember the exact details, this was a while ago. I think I did the change the day before when I got the warning email from Octopus.
WannabeOwner
Well-Known Member
Depends?
I have 2x PowerWall and 48 PV panels (and 2x 7kW EV chargers). Single phase. No DNO export limit (which was a surprise to me ...)
It mostly depend how much other PV is connected to the same low voltage cable as your home and how many properties to use your exports are connected to it.
PITA
Model 3 Performance
I'm hoping this will be in my favour then.
We have a small 3 Bedroom Detached house on a housing estate of about 100 houses.
Currently got a 7.2 kWp array with 5kW inverter, 2 x Powerwalls, 2 x 22kW Ev Chargers, 1 x 7kW Ev Charger...
So we're allowed 15 kW generation and 5 kW export.
... and I now want to add another 4 kWp South facing ground mounted system with a 4 kW inverter... for 11.2 kWp total.
I'm in the process of requesting a 100A per phase upgrade as well.
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PITA
Model 3 Performance
.... just to add to that.
Our Powerwalls charge at 10 kW... so that would handle the 9 kW peak solar rate.
The 7 kW Ev charger could transfer 7 kW to the cars... leaving 2 kW for house, which is easy with Heat Pump air conditioning turned on.
Our Powerwalls charge at 10 kW... so that would handle the 9 kW peak solar rate.
The 7 kW Ev charger could transfer 7 kW to the cars... leaving 2 kW for house, which is easy with Heat Pump air conditioning turned on.
WannabeOwner
Well-Known Member
I take from that that you are 3-Phase? I know diddly squit about it, but my understanding was that Export was far less of an issue for DNO on 3-Phase?
