Solar install, batteries, exporting and ev tariffs

[Nickj]

Just re read proposal, and does have an inverter still. I must have misunderstood what the installer said. The inverter does look more basic than previous one so is this saving money over original install comes?

Sponsored

 

[bn8959]

It’s normal for an inverter to be undersized compared to peak output from panels, as you’d not miss out on much (only the highest peaks get clipped) and it’s generally more efficient to run smaller inverters if possible.

seems like a very very good price!

it still looks like a massive inverter. 7kW?
If so, you must have a very friendly DNO, as you’d need an export allowance of 12kW (7kW from solar and 5kW from PW).

 

[Midlifecrisis]

Panels quote a peak output. If they all face the same way you may well achieve this at times. If they are on opposite side of the house then you won’t. A 7kW inverter should be fine for you. In practice you won’t discharge 12kW to the grid because your battery won’t be discharging when the sun is out. It will be charging

 

[Nickj]

It’s normal for an inverter to be undersized compared to peak output from panels, as you’d not miss out on much (only the highest peaks get clipped) and it’s generally more efficient to run smaller inverters if possible.

seems like a very very good price!

it still looks like a massive inverter. 7kW?
If so, you must have a very friendly DNO, as you’d need an export allowance of 12kW (7kW from solar and 5kW from PW).

The inverter quoted is the 8kw one so bigger. DNO came back with cap of 7kw. Does this mean the inverter gets capped or the powerwall gets capped? And any negatives if it’s the PW?

panels peak is 7.74kw

 

[bn8959]

The inverter quoted is the 8kw one so bigger. DNO came back with cap of 7kw. Does this mean the inverter gets capped or the powerwall gets capped? And any negatives if it’s the PW?

panels peak is 7.74kw

The DNO will always cap absolute peak theoretical output. So I can’t see how that is going to work.
You cannot have any combination that would export more than 7kW.
The PW is 5kW, but can be set to G98 mode, which will cap it to 3.6kW - which would completely cap its discharge AND charge rate to 3.6 - irrespective if you arnot exporting any of it. That would then only leave 3.4kW for your inverter peak output. It doesn’t matter if you don’t have the intention of exporting.

I have a 8.6kW limit. PW is in G99 mode - so full 5kW and I am limited to a 3.6kW inverter. I have 6kWp of panels and don’t miss much due to clipping.

Sounds like you’d be better off with a DC coupled battery for now and a 7kW inverter.

 

[bn8959]

The DNO will always cap absolute peak theoretical output. So I can’t see how that is going to work.
You cannot have any combination that would export more than 7kW.
The PW is 5kW, but can be set to G98 mode, which will cap it to 3.6kW - which would completely cap its discharge AND charge rate to 3.6 - irrespective if you arnot exporting any of it. That would then only leave 3.4kW for your inverter peak output. It doesn’t matter if you don’t have the intention of exporting.

I have a 8.6kW limit. PW is in G99 mode - so full 5kW and I am limited to a 3.6kW inverter. I have 6kWp of panels and don’t miss much due to clipping.

Sounds like you’d be better off with a DC coupled battery for now and a 7kW inverter.

Note my panels are 60% SW and 40% NE facing (on a low pitch roof), so I’d never get to peak panel output anyway.

 

[Nickj]

The DNO will always cap absolute peak theoretical output. So I can’t see how that is going to work.
You cannot have any combination that would export more than 7kW.
The PW is 5kW, but can be set to G98 mode, which will cap it to 3.6kW - which would completely cap its discharge AND charge rate to 3.6 - irrespective if you arnot exporting any of it. That would then only leave 3.4kW for your inverter peak output. It doesn’t matter if you don’t have the intention of exporting.

I have a 8.6kW limit. PW is in G99 mode - so full 5kW and I am limited to a 3.6kW inverter. I have 6kWp of panels and don’t miss much due to clipping.

Sounds like you’d be better off with a DC coupled battery for now and a 7kW inverter.

Hmm, this doesn’t sound good. Was getting rather excited about the Tesla PW 2!

Sorry, as a novice the DNO cap, but how does this work in reality? Do the installers put a program on the inverter or PW2?

I’m thinking I will export a fair amount, so is there no way of limiting this set up to 7kw?

when you say the pw is 5kw does that mean I couldn’t export at 7kw?

have emailed the installer with this query.

 

[bn8959]

Hi

The PW2 is effectively totally independent of your solar and inverter. They sit side by side and can operate separately. Each can power your home and each can generate independently (so 8kW from inverter and 5kW from PW2 - 13kW total), which can be used by your house or exported.

Of course in normal operation, the PW2 monitors the solar generation (ie the output from the inverter) and also monitors the flow to and from the grid. This allows it to charge from solar if it needs. PW2 will only export if configured to, and cost effective (you tell it your import and export rate and let it decide whats best). Generally, my PW2 never exports - you'd need several PW2's I suspect.

The challenge is around the DNO - they are concerned about the peak possible flow to the grid from your system - they don't care about how its configured. The argument is that if you set the system to 'only' export a max of 7kW to the grid (but it could generate more than that, for example if your house is using some too), they wont accept that because 'what-if' a sensor was wrong and it exported more, also a limit set in the inverter or PW2 would never react instantly - so the DNO requires a hard limit to align with the export limit they assign you. Lets say, for example, you had all your ovens on and where charging your car, and your solar was going full tilt - you could be generating 13kW (all of which would be being used by your house) - if a breaker suddenly tripped on your main fuse box, you could in theory, for a very very brief fraction of a second suddenly send that to the grid - which could cause a local voltage or frequency spike.

My info is a couple of years old - so maybe its out of date - maybe the inverter and PW2 can now be programmed to limit its grid export, or maybe your DNO is happy to allow that situation. Im not certain.

I'd just clarify with your solar people - check what your inverter will output to the house, and what it will output to the grid (peak), and check what the discharge and charge rate of the PW2 will be (again to your house and to the grid). Ask them how that aligns with a DNO 7kW export limit.

If you have a DC couple battery, then that sits 'behind' your inverter - so you only have the one device connected to your house/grid - so only the one device to be limited by the DNO. As you say though - PW2 is the best battery system available.

I want both! I want to add a DC battery so I don't lose my clipped peak output.

 

[Nickj]

Side note. Any views on if a need a zappi ev charger? Been pondering if my old point needs replacing? The hybrid Evoque would be charged over night on OI at 7.5p and I’m not at home most days to charge the taycan. Does the zappi gain me anything for £720 extra over my 3.5 year old Pp?

 

[bn8959]

Does your old EVSE integrate with OI?
I have a Zappi but don’t use it for its solar integration really. It’s connected to OI though. I find it much better to have the EVSE integrated with OI than the car - just works better, and would support more than one car too (plus some other sneaky benefits of getting longer at the 7.5p rate).

Also, if you are getting a PW2 - or any battery that is AC coupled - I strongly ask your electrician to make sure the EVSE is wired ‘grid side’ of the PW2 - this makes the PW2 completely unaware of the car charging and will never try to discharge to it. Car charging - especially if using the Solar excess capability of the Zappi - messes up the PW2’s intelligent planning.

 

[Nickj]

Does your old EVSE integrate with OI?
I have a Zappi but don’t use it for its solar integration really. It’s connected to OI though. I find it much better to have the EVSE integrated with OI than the car - just works better, and would support more than one car too (plus some other sneaky benefits of getting longer at the 7.5p rate).

Also, if you are getting a PW2 - or any battery that is AC coupled - I strongly ask your electrician to make sure the EVSE is wired ‘grid side’ of the PW2 - this makes the PW2 completely unaware of the car charging and will never try to discharge to it. Car charging - especially if using the Solar excess capability of the Zappi - messes up the PW2’s intelligent planning.

Current EVSE is a pod point, and it does integrate with OI but via the Porsche app I believe, so only with compatible cars. This is fine as the the wife’s evoque hybrid has a 13kw battery I trickle charge on a timer for he 6 hours. With OI sometimes I just use the timer on the pod point to charge for 6 hours and don’t use the intelligent part at all.

So, I don’t really need multiple car integration, and works fine as is, so not sure what the zappi will bring me?

Thanks for the tip on wiring. Will be sure to mention it.

 

[lcarron]

It is amazing that you can have enough energy with so small system as the overcast is pretty high in the UK.
Yesterday we produced 132 kw.
Here is a snapshot as I’m changing the lightning directly from the Solar system.

 

[Corkage Time]

I've got a similar setup - 4kW PV (south facing), 3.6kW inverter (Solax), Zappi and a PW2. All were installed at different times but they integrate well.

PW2 is enough to support the house for the day (except the depth of winter a few times) and is set to charge off-peak from grid. Export is through FiT (grandfathered in when buying the house) and peaks around 3.2kW as there are always a few things on in the house that takes ~0.4kW.

If required, the house can use up to 5kW from the PW2 plus whatever is generated from solar. Solar throughput is limited by the inverter at 3.6kW.

For example, looking right now with full sun I see battery at 100% (idle), PV generating 3.6kW (limited by inverter), house taking 0.4kW, and we're exporting 3.2kW.

The reason I went with PW2 is that it offers whole-house backup, where I researched other batteries that could only support one mains ring in the house that had to be configured on install. We have quite a few small outages in mains (rural) and the PW2 kicks in almost immediately no probs.

We're on IO but I configure the EV to charge overnight through the EV app (we have 2x EV), not Octopus app.

Another thing offered by IO are the free energy time slots where the grid has excess renewables available. Generally these are 3 hour slots that you get a heads-up about 1 day in advance and opt-in. You are encouraged to use as much energy as you want and get reimbursed for it - so switch everything on that you need to and set the PW2 to be 100% backup reserve, meaning it only recharges and will not serve the house unless there is an outage.

 

[Midlifecrisis]

.

Another thing offered by IO are the free energy time slots where the grid has excess renewables available. Generally these are 3 hour slots that you get a heads-up about 1 day in advance and opt-in. You are encouraged to use as much energy as you want and get reimbursed for it - so switch everything on that you need to and set the PW2 to be 100% backup reserve, meaning it only recharges and will not serve the house unless there is an outage.

I am on Octopus Intelligent and have never seen one of these. Where do they advertise them? Is it like the saving sessions on the app and their WhatsApp?

 

[bn8959]

I am on Octopus Intelligent and have never seen one of these. Where do they advertise them? Is it like the saving sessions on the app and their WhatsApp?

I was wondering that too. Seems like it’s a beta service only available in the South East currently:
https://octopus.energy/power-ups/

Sponsored