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Solar Panels UK - is it worth it?

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#3,121
WannabeOwner said:
doubt it will stay that way
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My post was ambiguous.... I was thinking that if you add up all energy for many homes (gas, electric, vehicle) you will struggle to generate enough from a typical roof area.

I hope that you are correct that eventually there is a pricing mechanism that pays for export based on time. However, I can see many challenges. It may be each home gets an export allowance of say 3.6kw that they can earn from. But the grid can't just say 'give us whatever you've got now' to all systems, not knowing which will chose to export at that moment.

I found out a couple of months ago that despite having had smets2 meter for several months and confirmation that it is working as it should, they still want me to submit manual readings!
 
#3,122
WannabeOwner said:
I doubt it will stay that way - although it will for anyone exporting at periods of oversupply when "no one wants it" (even then grid-scale storage could mop it up "cheap" and export it later at "peak"). Exporting at times of high demand, from your home-battery/EV H2G, will be better (for grid operator) than firing up a peaker-plant - battery comes on stream much faster, so less need to rely on predicting excess-demand, and can scale - e.g. individual household battery systems could be requisitioned and/or AMPs defined (to match supply with demand). Battery doesn't have the ability to run for days/weeks though :( which, in extremis, the peaker plants could.



Still likely to have the situation where everything is full and you are exporting. Last year I magically managed to drive trips that used up the PV from the Sun that then shone - averaging about 70 miles a day through the summer. This year my mileage is way down and I'm exporting a lot more :(

It might be better than no one has a house battery, nor PV panels, and both of those are constructed at "grid scale" economy-of-scale, and folk just "buy from the grid". As grid-scale batteries become cheaper they will supplant peaker-plants (already happening in some places), they will also drive down the price of peak electricity as peaker-plant generation is replaced with battery-discharge, and maybe we wind up with a single price tarrif (which should be one that is more equitable than now, so long as supply-and-demand free-market is available)

Might be I'm having a pipe-dream though ...
Click to expand...
2 EVs + home battery and I still don't have enough places to put the energy generated from my 10 East 405W and 7 West 405W panels for 50%+ of the year.
 
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#3,125
Grid flexing... 😀

Screenshot_20230722_233827_myenergi.jpg
 
#3,130
ACarneiro said:
Don't think I ever asked: is your solar inverter 3 phase as well?

100A single phase is getting a bit tight for me in the depths of winter (and that is with only one EV) so might consider taking the plunge to 3 Phase if and when the Powerwall system ever properly supports 3 Phases...
Click to expand...

Our Solar Inverter is Single Phase supplying two Powerwalls on L1.

The Tesla Gateway 2 can be configured for 3 Phase. With a minimum of one Powerwall on each phase. You can then buy a 3 Phase solar inverter to feed all three Powerwalls if you want.

So as far as I'm aware, it's already possible.
 
#3,132
ACarneiro said:
It doesn’t supply all three phases during a power cut and, as far as I’m aware, it does vector sum on the meter rather than properly getting power flow on all the phases (or maybe I read wrong information but that was my understanding).
Click to expand...

If you had a 3 Phase supply, a Tesla Gateway 2 configured for 3 Phase Supply, a 3 Phase Solar Inverter and three Powerwalls (one on each phase), I cannot see any reason why this system wouldn't work during a Grid blackout.

However, if you only had a single Powerwall on a Single phase on the above system, then that wouldn't work. Because the other two phases without a Powerwall attached would shut down the 3 phase solar inverter during a Grid blackout.

That's my understanding
 
#3,133
How our system works is like this.

We have a 3 Phase supply into a 3 phase distribution unit which supplies two 3 phase car chargers.

A single phase is then attached to a Tesla Gateway 2, two Powerwalls and a single phase solar array to a single phase consumer unit supplying the house and a 7kW car charger.

So if we have a Grid Blackout, all our house is protected by two Powerwalls. But the two 3 phase car chargers now won't work. But the single phase 7kW car charger will work as it's on the backup side.

It works for us.
 
#3,135
Avendit said:
Right, 2 systems, not really talking to each other, so the Pw's show up as load.

Should have been able to work that out, sorry.
Click to expand...

Before the MyEnergi V5 update... everything did talk to each other.

The Powerwalls were seen as Battery, everything else correct, Solar, Home, Car Chargers... all working correctly with all the Zappis linked and load balancing.

But since the version 5 update, it's royally screwed it all up.

What I'm waiting for now is MyEnergi to fix it back to where we were.
 
#3,136
The 'lucky' part is that I can still manually use the Zappi car chargers, rather than them being 'broke' by the V5 software update.

Our system is actually perfect in that Intelligent Octopus cannot interfere with the Battery system, Solar Array or home use... while charging from either 3 phase charger at any time during the day, on their cheap rate tariff. Octopus can mess about as much as they like charging the cars, doesn't affect the rest of the house.

So it all works great (except MyEnergi V5 update)
 
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#3,137
powerrouter life generation jul23.jpg


10 year data for the oldest part of my system. 6kwp of built-in panels, so not especially efficient, and certainly not compared with best panels available today.

System cost (excluding panel install which was part of new build roof) approx £3000 inverter, £3500 batteries, £8500 panels =£15000.

10 x £700 pa FIT inc deemed export.

The solar yield is interesting but academic.

useful energy from battery, say £0.30 * 15000 = £4500.
used directly from panel output £0.30 * 24780 = £7434

That's 11934 exc FIT. So, if you include FIT, the kit has paid for itself, but it isn't quite as overwhelmingly clearcut as I would have imagined. Thanks to my present tariff (5p night / 45p day) the value of battery stored energy is higher. Rationale moving forwards is not easy to determine. This part of the system has lead-acid. That's great because I can replace batteries no hassle any time, and if the inverter then failed, It's easy to swap out sticking with same batteries. Much harder and less certain with lithium subsystem approach.

The system 'wasted' about 3800 kWh (yield - used - exported). That's a chunk of energy worth may be £1-2000 depending how you value it. Old batteries 'waste' more energy and store less. Battery energy in vs out shows a loss of 5000 kWh! But keeping the system going unchanged til it dies doesn't cost me any new outlay and has a big impact on the initial system economics.

Charging the car solar vs overnight doesn't make sense with 5p / unit night electricity. That runs for another 12 months during which time my objective has to be to avoid any daytime use at 45p / unit. Of course that's likely to all change for me next year, at which time will there be viable smart export tariffs? I doubt they would justify coming off the old FIT I'm on. Having a EV with biggest available battery can be a good place to store excess PV, and if the vehicle is used primarily for local runs and parked at home during the day, then that negates the value of additional battery storage. More so with Zappi type devices that can adjust car charge rate.

You end up needing to have a very clear objective. Maximise income / profit, minimise grid dependence, minimise eco-negatives, own latest tech. Trying to optimise between such disparate goals is impossible!
 
#3,138
By contrast I’m a month into my £20k install (20× 430 W panels, 21.5% efficiency, 8 kW inverter, 14 kWh storage, DHW diverter) with bill credit of £7.47.

Not bad considering export payments only began a week ago. The energy arbitrage helping offset overnight EV+storage charging cost (18.4 p/kWh).

What’s also changed from 10 years ago: Smart meters logging half-hourly and smart tariffs such as Octopus Energy Flux.
 
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