Solar panels and battery - any real world reccomendations?

[HungryHippos]

Had a quote for a 7.5 Kw system with a Tesla Powerwall 2 for £17400.00. This is made up of 19 JA solar panels in an east/west configuration. The price breakdown is £9300 for the panels and £8126 for the Powerwall (installed prices).

My real question is whether the Powerwall is worth the money? There must be other systems that do the same job but are cheaper. Any thoughts?

When I was looking at it, the real draw of the Powerwall is the ability to get onto the Tesla Energy Plan with Octopus.

At the time this was 11p/kwh for electric, both import and export. I saw more recently this is now more like 24p/kwh (same again though, both import and export).

This means your generation and usage is neutral, you don't pay too much for using the grid, and you get paid pretty well for generation, and it really doesn't matter if you store, use, or generate units, as your costs are the same.

The other benefit that seemed to exist out of the box was whole home UPS mode, I think with Tesla by default it lets you work if the grid goes down, and the battery storage was reasonable enough to last a while. Other batteries on the market didn't offer this by default, though it sounded possible to do if you paid a bit extra to someone to configure it.

The negatives were that to make the battery worthwhile, you rely entirely on Octopus providing this plan, if they stop, then you just have a normal battery. I also understand that for some reason, Tesla battery was charged at 20% VAT even though other batteries are 0% VAT when bought with a solar installation.

If you have an EV, then off-peak Octopus GO to larger/cheaper batteries might be better. Off-peak charging/pricing is cheaper, and you can fill up EV + Home Battery for less cost per unit, even when Solar isn't effective due to winter time.

TL : DR:

Pros:

• Cheaper unit rates than regular fix tariffs.
• Better payment for generation which scales with import pricing (next best SEG is like 5-7p/kwh).
• Large battery with potential for UPS whole of home.

Cons:

• Battery is expensive per kwh of storage, possibly 20% VAT when other batteries don't have the same VAT rating.
• Tied to TEP plan with Octopus, no other supplier offers a specific Tesla plan
• Octopus GO may be a better alternative with EV + Cheaper battery.

I decided to go with an alternative instead, because there is a risk of the terms changing on the TEP plan.

 

[Siliconslave]

Thought it was neigh on impossible to get powerwalls these days?

The tesla plan is a bit odd as well, they manage the battery for you so it'll drain out to the grid when it wants to (as i understood it) so while the UPS mode is pretty cool how long it'll last is tied to how much its been de-charged by the grid

 

[HungryHippos]

Thought it was neigh on impossible to get powerwalls these days?

The tesla plan is a bit odd as well, they manage the battery for you so it'll drain out to the grid when it wants to (as i understood it) so while the UPS mode is pretty cool how long it'll last is tied to how much its been de-charged by the grid

True, I guess they won't completely empty it unless they really need to though.

 

[Mickie]

Just bought a solar diverter for an immersion heater but I don’t have a water cylinder. Was planning on heating a 2kw electric radiator. Wonder if there's anything else that it could power.

 

[SBo]

When I was looking at it, the real draw of the Powerwall is the ability to get onto the Tesla Energy Plan with Octopus.
...
I decided to go with an alternative instead, because there is a risk of the terms changing on the TEP plan.

Good choice, Powerwalls are so expensive they push the breakeven out by years, when I did the sums back it April it pushed the breakeven for my setup well beyond the expected life of the Powerwall even once adjusted for the special Tesla import rate on Octopus.
Not that its what I've gone for but you can also recreate the "Powerwall look" with other brands now. I've seen some quite smart GroWatt installs of late in that style.

By the way a simple UPS/EPS setup is very each to achieve with most hybrid inverters.

With the weather of the last couple of days I've done my first meaningful import (5kwh/day ish) from the grid for the first time since my system was installed in May .
Export rates peaked at over 60p kwh yesterday evening and I could do nothing!! I might need to move to GO earlier in the year than I expected.

 

[BUDFORCE]

Worst day for generation since install yesterday, was very overcast all day only generated 4.2kw.

 

[SBo]

Does anyone has a view on Hypervolt vs Zappi car chargers? They're the two reasonably priced car charger options that I've seen that can be set to charge off solar only.



I'm aware that SolarEdge also offer that capability if you have their kit.

 

[gpuerrilla]

Worst day for generation since install yesterday, was very overcast all day only generated 4.2kw.

Yeah been poor since the last day of the mini 'heatwave' here. I hope one day these Indian summers materialise!

 

[gailjon]

When I was looking at it, the real draw of the Powerwall is the ability to get onto the Tesla Energy Plan with Octopus.

At the time this was 11p/kwh for electric, both import and export. I saw more recently this is now more like 24p/kwh (same again though, both import and export).

This means your generation and usage is neutral, you don't pay too much for using the grid, and you get paid pretty well for generation, and it really doesn't matter if you store, use, or generate units, as your costs are the same.

The other benefit that seemed to exist out of the box was whole home UPS mode, I think with Tesla by default it lets you work if the grid goes down, and the battery storage was reasonable enough to last a while. Other batteries on the market didn't offer this by default, though it sounded possible to do if you paid a bit extra to someone to configure it.

The negatives were that to make the battery worthwhile, you rely entirely on Octopus providing this plan, if they stop, then you just have a normal battery. I also understand that for some reason, Tesla battery was charged at 20% VAT even though other batteries are 0% VAT when bought with a solar installation.

If you have an EV, then off-peak Octopus GO to larger/cheaper batteries might be better. Off-peak charging/pricing is cheaper, and you can fill up EV + Home Battery for less cost per unit, even when Solar isn't effective due to winter time.

TL : DR:

Pros:

• Cheaper unit rates than regular fix tariffs.
• Better payment for generation which scales with import pricing (next best SEG is like 5-7p/kwh).
• Large battery with potential for UPS whole of home.

Cons:

• Battery is expensive per kwh of storage, possibly 20% VAT when other batteries don't have the same VAT rating.
• Tied to TEP plan with Octopus, no other supplier offers a specific Tesla plan
• Octopus GO may be a better alternative with EV + Cheaper battery.

I decided to go with an alternative instead, because there is a risk of the terms changing on the TEP plan.

Thanks for that excellent explanation! I was also thinking a larger, less expensive battery would be better as we do have an EV and are on Octopus Go.

I am not sure I would want to be on the vagaries of a brand specific deal like the Tesla one as you never know what might happen. Also we are looking at a heat store technology to replace our oil boiler (think ZEB but larger).

 

[SoliD]

Does anyone has a view on Hypervolt vs Zappi car chargers? They're the two reasonably priced car charger options that I've seen that can be set to charge off solar only.



I'm aware that SolarEdge also offer that capability if you have their kit.

I've got a Zappi installed, but due to EV delay I've not had any use out of it whatsoever yet... Looks fine if quite large and the app is relatively basic but seems to have good functionality. Guy who installed it said it was much of a muchness between the two.

 

[b0rn2sk8]

Does anyone has a view on Hypervolt vs Zappi car chargers? They're the two reasonably priced car charger options that I've seen that can be set to charge off solar only.



I'm aware that SolarEdge also offer that capability if you have their kit.

I don’t agree there is a much of a muchness between the two.

Zappi has better, more polished functionality, particularly if you also want their solar hot water diverter (Eddi) product, they both work together very well.

Hypervolt looks a lot better but that’s it’s only real advantage over the Zappi.

I have a hypervolt, so I can answer any questions you may have on that.

 

[SBo]

Thanks guys. Do you think the lack of a screen and controls on the hypervolt unit itself is a negative from the standpoint of convenience and speed of unhooking the car and having to open an app to stop it charging to do that? Or is that not how it works?

I note that the hypervolt is about £100 cheaper.

Also been quoted about £100 (so ~£600 cheaper!) to just have a 32amp commando/ceeform socket installed in my garage since Audis come with a commando charger as standard. Obvi can't solar charge off that but the price saving is substancial and I can still timer charge off it with GO, so you're talking 8,000kwh @ 7.5p that you would need to switch to solar to break even on the charger. I have a mileage allowance of 10k miles a year so call that about about 2,800 kwh of charging a year @ 3.57 miles per kWh which google tells me is the combined enegy consumption for the Q4. I think I've just talked myself out of getting a fixed charger.

 

[b0rn2sk8]

I don’t think I would be worried about the lack of a screen, the app is what controls it mainly.

You don’t use the charger app for plugging and unplugging, it’s mainly for scheduling, changing modes etc. The car locks the cable, not the charger. So it’s what ever procedure you need to follow on that car. I think the Audi you unlock it and there is a button on the charge port to release the cable.

I can’t see how they can install a commando for £100 and it be compliant. For it to comply with the regs on EV charging you need an interlocking socket, an earth rod or a earth fault detection device. The latter is over £100 on its own. It’s a bit of a gray area as to whether they are even allowed in domestic settings.

Do you have a hot water cylinder? If so, the Zappi is the one to get. If not then either is probably fine.

I’d get a proper charge point installed with all the proper functionality. You are spending tens of thousands on a car, to be worrying about saving a few £ on a charge point seems a bit superfluous.

 

[HungryHippos]

Thanks for that excellent explanation! I was also thinking a larger, less expensive battery would be better as we do have an EV and are on Octopus Go.

I am not sure I would want to be on the vagaries of a brand specific deal like the Tesla one as you never know what might happen. Also we are looking at a heat store technology to replace our oil boiler (think ZEB but larger).

No problem, you'd be best sticking on GO then I reckon with a different battery.

Other manufacturers make batteries, my one being installed is a Givenergy. They go fairly big on those, I was quoted for an 8.2kwh but the newest version they make is 9.5kwh, not sure which one I'll wind up with as when I ordered mine the 8.2kwh was being phased out and hard to get hold of.

There are other people making them though, but £ per kwh they should more or less all beat Tesla powerwall.

 

[SoliD]

Regards the Eddi, I have a combi boiler, so no tank, but wondering if anyone had seen any solutions for a potential smaller pre heating tank that could use excess solar prior to going into the boiler or adding something into a system to allow the use of any excess, more for the summer when it's whacking out 5kwh and exporting 1 or 2kwh.

 

[SBo]

I don’t think I would be worried about the lack of a screen, the app is what controls it mainly.

You don’t use the charger app for plugging and unplugging, it’s mainly for scheduling, changing modes etc. The car locks the cable, not the charger. So it’s what ever procedure you need to follow on that car. I think the Audi you unlock it and there is a button on the charge port to release the cable.

I can’t see how they can install a commando for £100 and it be compliant. For it to comply with the regs on EV charging you need an interlocking socket, an earth rod or a earth fault detection device. The latter is over £100 on its own. It’s a bit of a gray area as to whether they are even allowed in domestic settings.

Do you have a hot water cylinder? If so, the Zappi is the one to get. If not then either is probably fine.

I’d get a proper charge point installed with all the proper functionality. You are spending tens of thousands on a car, to be worrying about saving a few £ on a charge point seems a bit superfluous.

Thanks for the thoughtful reply matey, helpful.

Yes noted re earthing arrangements, I did a bit of digging there, it applies if you have a TNC-S/PME supply and your plug/charging is outside as opposed to in a dry garage with a concrete floor as in my case. Otherwise you do require something like this https://www.replenishh.com/garo-g6e...o-pme-fault-det-connection-unit-6-way-65-3763 which adds £130 odd OR a TT earthing arrangement (ie rod) as you say to the commando socket route.
Apparently no issue with commando sockets in domestic as long as inter-locked thereby meeting the requirement for shutters on sockets in BS7671.

I have a sparky as a brother-in-law hence no install cost either way.

Something for me to think about. The breakevens I calculated in my post above surprised me how far out they were.

 

[HungryHippos]

By the way a simple UPS/EPS setup is very each to achieve with most hybrid inverters.

I was going to check this in more detail if we start hitting power cuts due to supply issues, but even with all that has gone on, I can't remember the last time I had a power cut.

 

[SBo]

..

 

[b0rn2sk8]

Regards the Zappi thing, I have a combi boiler, so no tank, but wondering if anyone had seen any solutions for a potential smaller pre heating tank that could use excess solar prior to going into the boiler or adding something into a system to allow the use of any excess, more for the summer when it's whacking out 5kwh and exporting 1 or 2kwh.

The cost will not outweigh the benefits, you’d be better off with battery storage or just exporting.

If you ever rip out that heating system then that’s the opportunity to install a proper hot water tank.

Thanks for the thoughtful reply matey, helpful.

Yes noted re earthing arrangements, I did a bit of digging there, it applies if you have a TNC-S/PME supply and your plug/charging is outside as opposed to in a dry garage with a concrete floor as in my case. Otherwise you do require something like this https://www.replenishh.com/garo-g6e...o-pme-fault-det-connection-unit-6-way-65-3763 which adds £130 odd OR a TT earthing arrangement (ie rod) as you say to the commando socket route.

I have a sparky as a brother-in-law hence no install cost either way.

Ah fair enough I didn’t spot it was a garage install. That said, to be really pedantic, it will still need its own earthing arrangement if you can get a cable to the outside.

I’d still get the proper charge point though. You’ll want to take your granny charger with you, the one time you need it is the time you forget to put it back in the car.

As it’s inside, I’d be inclined to get the Zappi but the hypervolt is still a decent option. The only reason I didn’t buy it is because it looks very fisher price on the front of a nice property with good curb appeal.

You might also want to consider if it’s worth having one with a cable that will reach outside so you can use the charger at times when you don’t want to put the car away.

 

[Tavis75]

Will chime in as another one who had their worst day of generation so far on Tuesday with 8.65KWh generated, which also coincided with my highest days usage of 11.41 (which was odd as other than the oven which I use nearly every day I did not use any high-draw appliances, on previous sunny days I've been running everything I can and not hit that level, so need to try and work out what was using the power). So battery actually went flat during the evening.

Got a DNO\G98\G99 question though, I have received a G98 letter from my DNO via my installer confirming installation of the system, but it is a 5.0KW Growatt solar inverter, 5.4KW of Panels, a 3.0KW Givenergy battery inverter and an 8.2KWh battery, so things I've read suggest it should require G99. Wondering if maybe the Growatt has an export limit to avoid needing G99 or something? Anyone more knowledgeable about this know why I may only have a G98?