I agree - I'll be adding that as an option for my control service this weekend. For me, the most efficient (from a cost point of view) is to not self consume at all on the weekend (off peak is 10.98c including GST, feed in is 11.3 cents including GST), so I need the battery to charge for Monday's peak over the weekend, but for every kWh of off peak that I draw from the battery, I have 10.98 cents, but I give up 13.29 cents of feed in - because it takes roughly 1.15kW of charging to allow 1.00kWh of discharging. I possibly should even consider no discharge off off-peak overnight at all - so that instead of re-charging the battery to make up for off-peak use, any excess is fed in.
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- Thread starter powersaver
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- Powerwall Tesla Energy
I agree - I'll be adding that as an option for my control service this weekend. For me, the most efficient (from a cost point of view) is to not self consume at all on the weekend (off peak is 10.98c including GST, feed in is 11.3 cents including GST), so I need the battery to charge for Monday's peak over the weekend, but for every kWh of off peak that I draw from the battery, I have 10.98 cents, but I give up 13.29 cents of feed in - because it takes roughly 1.15kW of charging to allow 1.00kWh of discharging. I possibly should even consider no discharge off off-peak overnight at all - so that instead of re-charging the battery to make up for off-peak use, any excess is fed in.
So, OK, someone agrees then.... my thoughts.... it costs more, energy wise, to recharge battery from off-peak (you'll lose 10-15%) than it does to export excess solar and receive FiT. The excess FiT then pays for any off-peak grid usage you use. Hopefully that will be more than you use. Then you save on wear and tear on the battery overnight during off-peak periods and save the capacity for the next morning Shoulder period. Solar will then start recharging the PW during the day. Which is all fine if solar forecast was 100% clear skies. Where it gets tricky is solar forecasting and winter loads.
What I think is a compromise is to set the reserve to the percentage remaining at 10pm (end of shoulder period M-F). The house uses grid at off-peak rates overnight. Then at 6:45am the next morning, set reserve to 0% so by 7am (start of shoulder) low solar production, the battery will service the house until solar production exceeds house consumption. Solar continues to service house and PW until the PW is 100%. The rest will be exported to grid. Keep house on self-powered mode to 10pm (covering Peak and shoulder periods). The pattern repeats to Friday. Then Friday night, set reserve to 100% and house is on grid for off-peak rates all weekend + solar. Any excess solar is exported. PW2 will be 100% charged by Monday 7am. And the cycle repeats....
Now, the tricky bit is getting the price differential between FiT and off-peak rates to work out which is the best way to go (taking into account energy/costs loss of 10-15% when recharging vs export). Recharge from grid to top up battery overnight at off-peak rates or reserve the battery overnight for next day's Peak/Shoulder periods until solar recharges for nothing. Hmmm..... my brain hurts now.... too many variables and scenarios with energy and costs calculations and which one maximises the best return!
Adding back to my own comments....
If I pay for off-peak usage from grid rather use the battery. I am paying profits to the retailer. Grrrrr. The battery avoids that scenario.
But then I would use the battery more and that results in wear and tear reducing it's future life capacity. So, what's the lesser of the two evils? Profits to retailers or wear and tear on battery?
I know that I will have excess solar production in Spring and Summer to meet house usage. Autumn sort of breaks even (this is where the battery is handy, it evens out solar production saved for night time use). But Winter, I know I will have to buy grid power, hence the question about recharging the battery vs using off-peak at night.
Thanks for the info. Any chance of a screenshot of the charge rate setup screen please? Cheers again
Dborn
Confirmed
My Powerwall is doing some funny things on TOU. (Cost saving settings. It charges to nearly full on off peak the instant off peak starts at 10pm. Then it starts discharging at around 4am. My first shoulder period begins at 7am, which is when I would expect it to first start discharging until solar production catches up and takes over to then feed the house and charge the battery. Also at times during the day it chooses to both feed the house and the battery but also send a small amount to the grid, like maybe 1 - 300 watts.
So I called support. I am told that the system is still gathering usage and consumption data and to give it at least 4 weeks to settle down. I have only had time of use since last Thursday.
So I called support. I am told that the system is still gathering usage and consumption data and to give it at least 4 weeks to settle down. I have only had time of use since last Thursday.
As I mentioned before, I was not happy with what TBC was doing during the first week. I turned it off and went back to Self-Powered, alternating between 90% reserve and 50% reserve as I had been doing before. After the storm passed, I turned TBC back on in Cost Saving mode. As noted above, my weekend rates don't have a shoulder period, just Peak and Off-Peak. Yesterday, Sunday, the system did exactly what I would expect from a properly running system. During Off-Peak, it let all the solar go to the batteries and the grid powered the house. When the batteries filled, it exported the surplus solar. When the Peak period started at 3pm, the batteries powered the house and all the solar was exported. When the Off-Peak rate resumed, it ended the solar export and the battery discharge and the grid powered the house.
Just had a look at the proposed network tariffs by Endeavour Energy (distributor in Sydney).... here is what they have proposed to the AER for their ToU 2018-2019 tariffs from 1 July 2018.
Peak tariff will decrease by 29.5%
Shoulder tariff will decrease by 6.6%
Off-peak tariff will increase by 35.5%
Daily supply charge will increase by 2.5%
But these are at the distributor level, what will be interesting is what the retailers will end up doing with the changes and whether they will follow the same percentages. If they do, off-peak tariff is going to be hit hard. Makes one think then that discharging in off-peak might not be so bad then.
Adding to this change, is that NSW iPart has recommended FiT to be reduced from 11c to 8c benchmark. Thus widening the gap between off-peak tariffs and FiT. So, less incentive to export.
And for those heavily reliant on ROI, these sort of changes affect it worse rather than better. Especially if peak rates are reduced by 29.5%!
Still waiting for the upgrade here. Does the changing take quickly? Currently any changes from Battery/Self-Powered takes 1 hour to register. We have a OhmConnect savings alert here and have to plan to change an entire hour early affect the selfpowered mode when we don't usually use it. Hoping the TOU setting is more responsive
I doubt it will. I expect the only quick way will be to update it via the API. I have OhmConnect also so I'm going to have to work around this myself, since I'm getting the SGIP credit and with needing to discharge regularly, this is going mess with my baseline.
Monday Peak hours just ended and TBC Cost Saving mode failed me again. It started the day with a very generous 84% SOC and exported all the surplus solar until the Peak period started at 2pm. Then it supplied the house loads from the Powerwalls and exported 100% of the solar. The Powerwalls hit the 50% Reserve at 8:40pm, short of the end of the Peak period at 9pm.
It makes no sense to me that the algorithm doesn't know that there is no Off-Peak solar available on weekdays. It's fine on the weekend when there is Off-Peak solar available, but it should charge with Surplus Solar during Part-Peak because it's the only way to store up energy for the Peak period during the week. I would be much more impressed if it calculated the charging rate required to hit a certain SOC, say 90%, by the start of the Peak period and exported the surplus above that. However, with Net Metering it doesn't really matter the charge rate, if there is enough solar production the batteries will eventually be full and the rest exported.
Am I expecting too much? Should I just give up on Cost Saving and fall back to Balanced to see what that does?
It makes no sense to me that the algorithm doesn't know that there is no Off-Peak solar available on weekdays. It's fine on the weekend when there is Off-Peak solar available, but it should charge with Surplus Solar during Part-Peak because it's the only way to store up energy for the Peak period during the week. I would be much more impressed if it calculated the charging rate required to hit a certain SOC, say 90%, by the start of the Peak period and exported the surplus above that. However, with Net Metering it doesn't really matter the charge rate, if there is enough solar production the batteries will eventually be full and the rest exported.
Am I expecting too much? Should I just give up on Cost Saving and fall back to Balanced to see what that does?
Mine does not take 1 hour to register. Any changes to my system take effect between 30 and 35 minutes past the hour. This behavior is very consistent. You can probably figure yours out by using the cursor function on the Today or Yesterday chart to see what time the behavior changes. If you've never used the Cursor function, just hold your finger on the chart in the App and it will show the values plotted for that time slot. Slide your finger around to different times.
I haven't been following your earlier reports, but the above sounds like the Powerwall got it 95% right, so I wouldn't call it a failure. It should have just charged a little during Part Peak to have more capacity to cover your Peak usage until 9 p.m. But 6-2/3 hours / 7 hours = 95%, so it almost got there. I think the real question is whether it will charge back up to 84% or a little higher tomorrow during Part Peak to be ready for Peak (apologies if you already covered this).
Also, if the algorithm isn't quite working the way you want it to, you may be able to alter its behavior by defining part of your morning Part Peak period as Off-Peak, to encourage it to charge more then.
Cheers, Wayne
Dborn
Confirmed
Prior post with initial reactions to TBC Cost Saving mode are in Post #46. You're the second person to suggest altering the rate schedule to modify the behavior. I'm not going to do that. I'm going to see what it does over the next couple sunny days and then maybe try the Balanced setting to see if that matches my expectations better than Cost Saving.
I would be satisfied with the implementation of two simple rules with the rest of the time being Self Powered.
1. Do not discharge from battery during Off-Peak.
2. Power the home from battery during Peak.
That's it. It's not that hard. What exactly is "learning for a month" going to gain beyond those two simple rules?
I was already basically accomplishing this by toggling the Self Powered Reserve from 50% to 90%. 50% when I wanted it to discharge and 90% when I didn't want it to discharge. Powering the home from battery and exporting 100% solar was not possible, but most of the time nobody's home on weekdays when the solar is generating during Peak hours.