Energy bill after Powerwall installation

[Vostok]

AGL also have a virtual power plant (VPP) bonus. $100 sign up and $45 /qt.

Before I churned from AGL I got a letter about this offer but didn’t take it up. Do you know whether AGL has drawn any power from your battery and do you receive a notification when it happens?

Net outcome (including VPP $180 pa) -$1070 pa

Wow. That is a decent slab of money coming in!

With Solar only $40 pa. No Solar $1909 pa.

How did you calculate these counterfactuals? I have developed my own spreadsheet, but curious to know how you did it

 

[jaykaye]

A single PW2 works across 3 phases with the new controller. It just wont provide power to 3 phase equipment in a blackout.

Interesting. Do you know if it would supply power to non-3phase equip across all 3 phases in a blackout?

 

[Amphead]

Interesting. Do you know if it would supply power to non-3phase equip across all 3 phases in a blackout?

No, it does not supply power across all 3 phases in a blackout. Nor does it (necessarily) have to backup everything you have on one phase, which is what I had initially assumed.

Instead, you can nominate one or more circuits as the "backup loads" to remain powered in the event of a blackout; for example, one or more light circuits, kitchen, etc. Consequently, these will all be on the same phase.

As a simplified explanation, from your main supply meter / switch, you'd have 3 cables feeding into (and being monitored) by the Backup Gateway 2, one for each phase, and then you'd have 4 coming out of the Backup Gateway back into your switchboard and home circuits - three for the usual three phases, and another which powers the nominated "backup loads" at all times (ie. normally and during a blackout).

 

[Vostok]

No, it does not supply power across all 3 phases in a blackout. Nor does it (necessarily) have to backup everything you have on one phase, which is what I had initially assumed.

Instead, you can nominate one or more circuits as the "backup loads" to remain powered in the event of a blackout; for example, one or more light circuits, kitchen, etc. Consequently, these will all be on the same phase.

As a simplified explanation, from your main supply meter / switch, you'd have 3 cables feeding into (and being monitored) by the Backup Gateway 2, one for each phase, and then you'd have 4 coming out of the Backup Gateway back into your switchboard and home circuits - three for the usual three phases, and another which powers the nominated "backup loads" at all times (ie. normally and during a blackout).

I’ve not heard of that being done, but the way my switchboards are configured it would not be possible in my situation anyway, because all the individual circuit switches are not in the outdoor meter box, therefore beyond the visibility of the PW2.

I have the meter box and main switchboard outside, which has the 3-phase switch in it to turn the entire property off, and two sub-boards inside (one in the house and one in the outbuilding) with individual switches for the light and power circuits as well as specific loads (e.g. oven, air conditioners, Tesla HPWC).

 

[Amphead]

I’ve not heard of that being done,

It is the option presented under Designing for Essential Load Backup here: System Design | Powerwall Support

How is your's set up? Backing up a whole phase?

but the way my switchboards are configured it would not be possible in my situation anyway, because all the individual circuit switches are not in the outdoor meter box, therefore beyond the visibility of the PW2.

I have the meter box and main switchboard outside, which has the 3-phase switch in it to turn the entire property off, and two sub-boards inside (one in the house and one in the outbuilding) with individual switches for the light and power circuits as well as specific loads (e.g. oven, air conditioners, Tesla HPWC).

Internal sub-board/s shouldn't preclude you from that option if you ever found it desirable for some reason. Unless I've misunderstood, this would require another isolation switch/breaker in the main switchboard for the essential load supply, then another cable run from this switch to the internal sub-board/s to allow whichever individual circuits you nominated to be switched over to that supply.

 

[paulp]

I’ve not heard of that being done, but the way my switchboards are configured it would not be possible in my situation anyway, because all the individual circuit switches are not in the outdoor meter box, therefore beyond the visibility of the PW2.

I have the meter box and main switchboard outside, which has the 3-phase switch in it to turn the entire property off, and two sub-boards inside (one in the house and one in the outbuilding) with individual switches for the light and power circuits as well as specific loads (e.g. oven, air conditioners, Tesla HPWC).

My understanding is you can only back up either one entire phase or any number of circuits on the same phase.
Fortunately when we built our house I did a bit of work with our very good sparky to ensure essential items were all on the same phase. What I’m not sure about yet but will be in a few weeks, is whether with 3 powerwalls each one can back up a phase.

 

[Vostok]

How is your's set up? Backing up a whole phase?

Yes. My PW2 backs up Phase A, chosen because over the prior 12 months it used the most power. But I don’t know which circuits run off Phase A.

I recently tried to detect which circuit runs off which phase by plugging in a 10A heater to various sockets, and going through the meter menus to observe the kW on each phase. There was only background power consumption otherwise at the time, so the 2.4 kW should have been really obvious. But the results were totally weird.

On one circuit I could see no power increase on any phase. That’s possibly the phase the PW2 is serving, so the meter saw no increase. On all other circuits, the power increase appeared on two phases, either Phase A and B, or Phase B and C. That I can’t explain.

Internal sub-board/s shouldn't preclude you from that option if you ever found it desirable for some reason. Unless I've misunderstood, this would require another isolation switch/breaker in the main switchboard for the essential load supply, then another cable run from this switch to the internal sub-board/s to allow whichever individual circuits you nominated to be switched over to that supply.

With my house I suspect it would have been very complicated/expensive if not impossible to that. As far as I know, the cabling from the meter box to the first sub-board runs through a concrete slab. And if not that, through a bunch of rafters that would only be accessible by ripping off the plasterboard ceiling.

 

[Amphead]

Yes. My PW2 backs up Phase A, chosen because over the prior 12 months it used the most power. But I don’t know which circuits run off Phase A.

Have you tried shutting off the main supply switch in your switchboard to simulate a grid failure? Whatever is still running after that will be your PW2 backed circuits.

 

[Vostok]

Have you tried shutting off the main supply switch in your switchboard to simulate a grid failure? Whatever is still running after that will be your PW2 backed circuits.

No, I haven’t done that. Mainly because I don’t want to have reset everything that is plugged into the non-backed-up phases. I might do it one day.

 

[pts260]

How did you calculate these counterfactuals? I have developed my own spreadsheet

Before I churned from AGL I got a letter about this offer but didn’t take it up. Do you know whether AGL has drawn any power from your battery and do you receive a notification when it happens?

Calculations, include daily rate for each scenario, peak rate, and feed in tariff.
No solar or battery. All "home usage" is peak.
Solar only. "Home usage" is peak subtract both "to grid" and "from power wall" as FIT
Solar and battery. Use "from grid" as peak use "to grid" as FIT.

As to the usage, no they haven't used in any significant way, more just to test I suspect. Even when grid spot price went to $14/kWh they didn't touch it.

When the VPP was enabled you get an extra icon called grid services. See attached. No notifications when they use it.

 

[Vostok]

Calculations, include daily rate for each scenario, peak rate, and feed in tariff.
No solar or battery. All "home usage" is peak.
Solar only. "Home usage" is peak subtract both "to grid" and "from power wall" as FIT
Solar and battery. Use "from grid" as peak use "to grid" as FIT.

Right, so you don’t have ToD tariffing and can directly substitute as above.

I made sure I moved to a ToD tariff after getting solar and then built a very complicated s/sheet to enable me to directly compare different plans from different suppliers based exactly on the 5-minute profile of my solar generation and usage. What it showed was that different tariffs can make hundreds of dollars difference to my bill. After 6 months of data, it was clear which tariff I should move to, which I did.

Generalisations based on my generation and consumption profile:

• Fixed rate or “general tariff” plans were always the worst ones, ToD ones better.
• Plans with the highest FIT were the best. These also had the highest peak rates, but...
• Peak rates unimportant because with solar plus a battery, consumption at peak times is very small. So very happy to take the highest FIT no matter how eye-watering the peak rate is.

 

[paulp]

Right, so you don’t have ToD tariffing and can directly substitute as above.

I made sure I moved to a ToD tariff after getting solar and then built a very complicated s/sheet to enable me to directly compare different plans from different suppliers based exactly on the 5-minute profile of my solar generation and usage. What it showed was that different tariffs can make hundreds of dollars difference to my bill. After 6 months of data, it was clear which tariff I should move to, which I did.

Generalisations based on my generation and consumption profile:

• Fixed rate or “general tariff” plans were always the worst ones, ToD ones better.
• Plans with the highest FIT were the best. These also had the highest peak rates, but...
• Peak rates unimportant because with solar plus a battery, consumption at peak times is very small. So very happy to take the highest FIT no matter how eye-watering the peak rate is.

I’ve done a lot of power bill calculations for a lot of people, and its rare in SA that the highest FIT plan has the best outcome. Its generally because they are also coupled with higher tarifs. I continue to tell people to model up a full year using various providers, and the end number is all that matters. Obviously if any assumptions change such as adding solar, batteries, or rates change, its best to remodel.

 

[jaykaye]

No, it does not supply power across all 3 phases in a blackout. Nor does it (necessarily) have to backup everything you have on one phase, which is what I had initially assumed.

Instead, you can nominate one or more circuits as the "backup loads" to remain powered in the event of a blackout; for example, one or more light circuits, kitchen, etc. Consequently, these will all be on the same phase.

As a simplified explanation, from your main supply meter / switch, you'd have 3 cables feeding into (and being monitored) by the Backup Gateway 2, one for each phase, and then you'd have 4 coming out of the Backup Gateway back into your switchboard and home circuits - three for the usual three phases, and another which powers the nominated "backup loads" at all times (ie. normally and during a blackout).

Thanks for the explanation. It makes sense.
I have all circuits for all 3 phases on a sub-board in the house with enough room for the Gateway2 if needed, but the solar panel connections are beside the outdoor meter box (not the inverter, i've got microinverters sitting under each panel). So if I wanted to install a PW2 I think I would need to move the solar panel stuff from the meter box to the sub board. Plus I would need to rearrange my circuits to have all the ones I want backed up on one phase. At the moment all lights are on one phase and all other sockets are spread across the other 2 phases.

 

[paulp]

Thanks for the explanation. It makes sense.
I have all circuits for all 3 phases on a sub-board in the house with enough room for the Gateway2 if needed, but the solar panel connections are beside the outdoor meter box (not the inverter, i've got microinverters sitting under each panel). So if I wanted to install a PW2 I think I would need to move the solar panel stuff from the meter box to the sub board. Plus I would need to rearrange my circuits to have all the ones I want backed up on one phase. At the moment all lights are on one phase and all other sockets are spread across the other 2 phases.

I also have micro-invertors that send power to the meter box. I’ve been advised by the installer that these 7 circuits will be connected into the Gateway2, which is needed. Fortunately the cable all run past the gateway 2 location.

 

[Amphead]

Thanks for the explanation. It makes sense.
I have all circuits for all 3 phases on a sub-board in the house with enough room for the Gateway2 if needed, but the solar panel connections are beside the outdoor meter box (not the inverter, i've got microinverters sitting under each panel). So if I wanted to install a PW2 I think I would need to move the solar panel stuff from the meter box to the sub board. Plus I would need to rearrange my circuits to have all the ones I want backed up on one phase. At the moment all lights are on one phase and all other sockets are spread across the other 2 phases.

If you can fit the Gateway2 next to the meter box, I’d put it there.

No need to move the solar panel stuff around then, just the sub-board rewiring - either to put the essential loads on one phase, or (with another cable run from the Gateway/meter board to the sub-board) to power just the nominated circuits.