Powerwall Gateway

[Anubis]

I’m wondering if Tesla sell the Powerwall Gateway only as a solution.
I have solar, but can’t use the generated solar when there is a grid power outage.
I see the gateway as a way of allowing the house to use the power generated by my solar system during the day when the grid power is unavailable.
If it’s doable, and not over the top expensive, I’d consider it.
I’m not ready for a full Powerwall install yet and see the gateway as a possible compromise.

 

[Mark E]

No, for that to work you need a battery of some description. The Solar inverters are designed specifically to follow the grid - not to generate one - and as such rely on it being present.

You also need some way to absorb/fill gaps between solar production and the house load, which is where the battery comes in. Interestingly enough when running in backup mode and the battery starts getting full, a power wall uses frequency shifts to control the output from solar once it gets to 96%.

I was watching our power wall do exactly that last week when we had the grid down for 34 hours. In the afternoon the solar could produce 4-6kW but the house was drawing only 3-400W. The solar was being shut down as the battery stabilised the house power.

 

[Anubis]

Thanks Mark, but I don’t totally understand this.
What happens in the scenario of the Powerwall being totally exhausted of charge and the grid has a power outage? Does the solar system still power the house?
Or is the problem that the solar may only producing 0.5kW and the house wants to use more, say 2kW?

 

[Mark E]

Thanks Mark, but I don’t totally understand this.
What happens in the scenario of the Powerwall being totally exhausted of charge and the grid has a power outage? Does the solar system still power the house?
Or is the problem that the solar may only producing 0.5kW and the house wants to use more, say 2kW?

The powerwall keeps the solar running for as long as possible and charges itself with any excess.

You need the battery to be able to absorb any excess from the solar and provide enough if the house load is more than the solar is producing. If, for arguement’ s sake the battery was depleted and the solar wasn’t producing enough to keep the house going then you’d be blacked out.

In my case recently the battery was down to 7% before the solar kicked in and recharged it to 96% - when it started to control the output of the solar. This was because the blackout happened after a day of bad weather so the battery was only around 30%. When fully charged the powerwall can run my house easily until the sun comes out the next day - generally with 50% or more left.

 

[Vostok]

Another complication is if you have 3-phase power, a PW2 will back up only one of the phases. You need 3 x PW2 to back up every phase, which in almost every case would be a complete waste of money.

Our PW2 was connected to the phase that, based on the previous 12 months bills, used the most amount of power (44%). But I have no idea which phase is connected to which (single-phase) house and light circuits, nor do I know an easy way to determine that. If the grid ever goes down, I will find out then (will the fridge and TV keep running? )

The PW2 gateway is smart though with the net metering. Even though the solar only directly feeds 1 phase (single phase inverter), the consumption on all 3 phases is measured and the system will inject into grid the amount of power needed to offset the total grid use. From a billing perspective, it’s as if the solar and PW2 were spread across all 3 phases.

 

[baillies]

Another complication is if you have 3-phase power, a PW2 will back up only one of the phases. You need 3 x PW2 to back up every phase, which in almost every case would be a complete waste of money.

Our PW2 was connected to the phase that, based on the previous 12 months bills, used the most amount of power (44%). But I have no idea which phase is connected to which (single-phase) house and light circuits, nor do I know an easy way to determine that. If the grid ever goes down, I will find out then (will the fridge and TV keep running? )

The PW2 gateway is smart though with the net metering. Even though the solar only directly feeds 1 phase (single phase inverter), the consumption on all 3 phases is measured and the system will inject into grid the amount of power needed to offset the total grid use. From a billing perspective, it’s as if the solar and PW2 were spread across all 3 phases.

can’t you just turn the grid connection off and walk around and test the lights and powerpoints? Hopefully you haven’t connected the powerwall to the hot water and oven circuit only ;-0

 

[Vostok]

can’t you just turn the grid connection off and walk around and test the lights and powerpoints? Hopefully you haven’t connected the powerwall to the hot water and oven circuit only ;-0

Ha ha You’ve spurred me on to find out... I can test each of the circuits in the house by plugging in a small 10A fan heater into one of the GPOs on each circuit, and looking at the amps on each phase reported by the grid meter. Light circuits might be harder since I now have LEDs everywhere, hence only small increases in current.

 

[paulp]

Ha ha You’ve spurred me on to find out... I can test each of the circuits in the house by plugging in a small 10A fan heater into one of the GPOs on each circuit, and looking at the amps on each phase reported by the grid meter. Light circuits might be harder since I now have LEDs everywhere, hence only small increases in current.

Or just turn off your meter isolator or incoming main switch and see what works

 

[Furfy]

Or just turn off your meter isolator or incoming main switch and see what works

Yep. that's what I did. In my case, everything works

 

[smithy]

You need 3 x PW2 to back up every phase, which in almost every case would be a complete waste of money.

My understanding is this won't work, as the PW2s would need to be talking to each other such that each phase is 120 degrees apart (required for appliances that use 3-phase power like ducted AC, which will be damaged if the phases aren't corrected synced). AFAIK this isn't possible with PW2s yet. I also doubt it is a priority as the market for 3 x PW2 and 3 phase is probably relatively small

 

[Vostok]

My understanding is this won't work, as the PW2s would need to be talking to each other such that each phase is 120 degrees apart (required for appliances that use 3-phase power like ducted AC, which will be damaged if the phases aren't corrected synced). AFAIK this isn't possible with PW2s yet. I also doubt it is a priority as the market for 3 x PW2 and 3 phase is probably relatively small

Good point! Didn’t think about that.

The second generation PW2 Gateway (which looks much nicer than Gen 1) is apparently 3-phase compatible and my understanding is it will inject power back into the grid on all 3 phases so from the grid supplier’s point of view plays much nicer (helps keep the phases balanced) than just injecting power on 1 phase. The PW2 itself though will still only power 1 phase in the house.

When I had my install done in May last year, my installer said if I waited a week I could be the first person in the country to have a Gen 2 Gateway installed, and that they would waive the extra installs costs (just have to pay the hardware delta) and they would treat it as a practical learning experience on how to install them at a site.

It was tempting but I elected not to, since postponing the solar install would have mucked up other renovation scheduling in my house.

 

[paulp]

Good point! Didn’t think about that.

The second generation PW2 Gateway (which looks much nicer than Gen 1) is apparently 3-phase compatible and my understanding is it will inject power back into the grid on all 3 phases so from the grid supplier’s point of view plays much nicer (helps keep the phases balanced) than just injecting power on 1 phase. The PW2 itself though will still only power 1 phase in the house.

Your comment above is consistent with what I was advised for my current installation, once the local power company approve it.