Solar Panels UK - is it worth it?

[garycat]

Solar panels certainly worth it yesterday. 31.1 kWh generated from a 4.3kW array. I only used 5kWh so that's enough for another 2-3 houses daily consumption. I think solar panels should be mandatory on any South facing roof, with generous grants to install them.

 

[Avendit]

Solar panels certainly worth it yesterday. 31.1 kWh generated from a 4.3kW array. I only used 5kWh so that's enough for another 2-3 houses daily consumption. I think solar panels should be mandatory on any South facing roof, with generous grants to install them.


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Strong agree. At least in Scotland you have to have some on new builds I think. Visiting England and walking past lots of new builds in the Dales with big blank roofs. Makes me sad.

OTOH, was a pants 9.5kw day at home in Edinburgh yesterday, kina glad we weren't there.

 

[Fursty Ferret]

I think solar panels should be mandatory on any South facing roof, with generous grants to install them.

Germany actually offers (offered?) extra grants for east/west roofs to calm the spike in generation. I've got an E/W array and got 26kWh out of it yesterday in North Yorkshire, but while the peak was lower (only 3kW) it generated power from 5.30am to 8.30pm.

 

[scdoubleu]

Aye, a west aspect can provide very decent power this time of year, particularly over the peak evening "cooking" period. Here's a snippet of our graphs yesterday:

I've highlighted just the (combined) solar in the top graph, and output from our two arrays in the bottom. Blue is south-facing garage array, pink is west-facing house array, each with a 3 kW inverter.

The house array doesn't contribute much Nov-Feb but outside those months can provide a welcome boost in the late afternoon/early evening.

 

[WannabeOwner]

I think solar panels should be mandatory on any South facing roof

Don't discount North roofs - provided not too steep in mid Summer they will produce 80% of a South roof. Obviously not the same ... but its not as terrible as I once thought

And personally I'm with @Fursty Ferret and @scdoubleu : an East/West roof starts making meaningful generation up to an hour earlier than a South roof, and same for the West roof in the evening (as does a North roof) ... so the "solar night" is up to 2 hours shorter, and thus the ability for a battery to support the house, overnight, needs less capacity. Also twice the roof area compared to the house next door with only a South array, and 75% more generation during the 8 summer-months

I tried PVWatts for my location, just for some comparative figures

kWh total for the year and kWh / %age for March-October

2,577 / 2,399 North 75%
3,095 / 2,812 East 87%
3,653 / 3,236 South 100%
3,132 / 2,851 West 88%

 

[ACarneiro]

Well, since installing my other Powerwalls I have managed to use even more of my solar generation.
So far this month I have used about 80kWh from the grid out of my 812kWh useage (and this is for cooking, hot water, driving and “the house”).

This is the time of the year where the investment seems more worthwhile. October to April is just depressing…

 

[Mrklaw]

this is my N/S array for yesterday. north is 4kw with a 3kw inverter, south is 2.6kw and I don’t know the inverter size. The interesting part is the earlier pickup

I can’t work out how to get kwh out of home assistant and myenergi doesn’t seem to surface a kwh sensor. Tried utility meter but its giving me wacky numbers so I’ve done something wrong.

 

[WannabeOwner]

this is my N/S array for yesterday

Perhaps this strengthens the case (which I hadn't considered before) for a battery. My energy generation is also affected by clouds passing overhead, causing fluctuations. Maybe, without a battery, it means the house is importing electricity from the grid during each low point? Whereas, with a battery, it can continue operating off-grid seamlessly, without any interruptions.

 

[Avendit]

Perhaps this strengthens the case (which I hadn't considered before) for a battery. My energy generation is also affected by clouds passing overhead, causing fluctuations. Maybe, without a battery, it means the house is importing electricity from the grid during each low point? Whereas, with a battery, it can continue operating off-grid seamlessly, without any interruptions.

Yep, battery decouples your generation from usage. Key to even slightly economic use I think. Battery can be li-ion or hot water, but you need some way of storing power as it's generated.

 

[Mrklaw]

Perhaps this strengthens the case (which I hadn't considered before) for a battery. My energy generation is also affected by clouds passing overhead, causing fluctuations. Maybe, without a battery, it means the house is importing electricity from the grid during each low point? Whereas, with a battery, it can continue operating off-grid seamlessly, without any interruptions.

yep. Also battery unlocked car charging for us for the same reason. Clouds/fluctuations would stop/start and my car would refuse to charge after a few. Battery lets me keep it running at 1.4kw minimum and then when there is excess it charges the battery back up while the charger stays at 1.4, then the excess goes to the car - so its buffering the EV charger like that too.

 

[WannabeOwner]

Clouds/fluctuations would stop/start and my car would refuse to charge after a few.

Repeated Stop/Start not good for contactors either ... dropping AMPs to, say, 5A when clouds come over would be better ... and then consume some battery until the clouds go away ... or SoC of battery drops below threshold (maybe just a percent or so) and wait for battery to gain those couple of percent before re-enabling "Charge car"

Do you have something (API widget maybe?) that alters AMPs based on PV generation excess?

I do have a Zappi but I don't use it in Eco-Plus mode for this reason

 

[Mrklaw]

Repeated Stop/Start not good for contactors either ... dropping AMPs to, say, 5A when clouds come over would be better ... and then consume some battery until the clouds go away ... or SoC of battery drops below threshold (maybe just a percent or so) and wait for battery to gain those couple of percent before re-enabling "Charge car"

Do you have something (API widget maybe?) that alters AMPs based on PV generation excess?

I do have a Zappi but I don't use it in Eco-Plus mode for this reason

isn’t 1.4kw already 6A? not sure how much lower it can get although I do read about people really trickling it in. previously I never had enough solar to bother, but now I have enough + a battery so that works for me without shenanigans.

eco+ you can also use a timer delay so it will continue to charge for a while to allow the sun to come back out but obvoiusly there its pulling from the grid without a battery. So Eco+battery is the best solution if you have that available.

 

[PITA]

Perhaps this strengthens the case (which I hadn't considered before) for a battery. My energy generation is also affected by clouds passing overhead, causing fluctuations. Maybe, without a battery, it means the house is importing electricity from the grid during each low point? Whereas, with a battery, it can continue operating off-grid seamlessly, without any interruptions.

That's how we work ours.

Our two Powerwalls can discharge at 10kW (plus any Solar kW on top).

This means we can use a full 7kW car charger at anytime to charge the car from battery storage only.

So long as the Powerwalls have stored energy in them.

We can then modulate the car charging from 7kW down to 1.4kW through the Tesla App. So we don't risk pulling from Grid if house demand spikes at any time.

 

[PITA]

In fact, that's exactly what I'm doing now.

Draining the Powerwalls into the car, at 4kW (20 Amps)... getting ready for tomorrow's full day of Sunshine.

 

[LampyDave]

Repeated Stop/Start not good for contactors either ... dropping AMPs to, say, 5A when clouds come over would be better ... and then consume some battery until the clouds go away ... or SoC of battery drops below threshold (maybe just a percent or so) and wait for battery to gain those couple of percent before re-enabling "Charge car"

Do you have something (API widget maybe?) that alters AMPs based on PV generation excess?

I do have a Zappi but I don't use it in Eco-Plus mode for this reason

You probably know this - but in case it's useful for someone else - on the Zappi app you can adjust the 'Eco percentage' to adjust how far the solar output has to drop before the car stops charging. The manual is a bit vague, but this forum post is easier to understand:

myenergi-What is Min Green Level?

I want to use this setting to control the amount of grid power that is used in charging. I have read and re-read the manual and app, but it just doesn

myenergi.info

We have ours in Eco+ and with MGL set to 10%. The Zappi doesn't start charging from 'excess' solar until there is export to the grid, but then the excess solar level can drop to 140W (10% of 1.4kW) before it stops charging. That avoids the charger stopping every time a cloud passes in front of the sun. It does mean that there is some electricity coming from the grid (or AC battery) while the solar dips, but that's less bothersome to me than the Zappi starting and stopping all the time.

 

[Mrklaw]

Regular eco mode will do pretty much the same thing. Triggers at 1.4, if solar drops below 1.4 it’ll pull the rest from the grid up to 1.4

 

[Mrklaw]

I wish the documentation on the zappi was better as it’s quite confusing how the different modes work

Some use cases showing increasing and decreasing load/solar etc would be helpful I think.

I didn’t even know there was a delay timer in eco+ mode also - so at 100% it can wait up to 4 minutes if a cloud goes over before it stops - also to help prevent too many changes

 

[WannabeOwner]

eco+ you can also use a timer delay so it will continue to charge for a while to allow the sun to come back out

You probably know this

No didn't know either . thanks.

the excess solar level can drop to 140W (10% of 1.4kW) before it stops charging

Not sure that's a lot better, but I may be being pedantic, and may not be a problem in practice.

Clouds come over, PV drops to 141W , Zappi carries on. Indefinitely? (well, come end-of-day PV will definitely drop below 140W ... and the cutoff could be chosen to support PV array for "most scenarios") ...

But I also foresee that power drops below 140W (or the "low PV" timer expires) at some point, and then the sun immediately comes out resulting in toggling. I am sure the low POV limit and/or the timer reduce the incidence, and maybe that is good enough.

But for anyone with a battery something using the API seems like a better bet than Eco+ to me - allow battery to drain, say, 5% then turn off car charging. If sun immediately comes back out it has got to make up the 5% to the battery before car charging will resume. So I think? hysteresis would be much better.

 

[GRiLLA]

Any other former First4Solar queueing customers on here?

Thankfully getting my deposit back from my credit card appears to have been straightforward, but I'm not really sure what to do now. Solar-Connect will b in touch again within a week or so, but it's really not clear what that arrangement will yield, they will gain a backlog of over 100 installs so hardly likely to be fast.

What's anyone else in a similar situation doing next?

 

[thewishy]

But for anyone with a battery something using the API seems like a better bet than Eco+ to me - allow battery to drain, say, 5% then turn off car charging. If sun immediately comes back out it has got to make up the 5% to the battery before car charging will resume. So I think? hysteresis would be much better.

If you're technical, I'd argue Zappi is less useful when you have a battery, unless you have Myenergi through the whole stack. It made a lot more sense without batteries

I'm using a Wallbox and OCPP via home assistance. Charging starts when the battery hits 90% (Leaves capacity for >3.6kw loads, which can be fed into the battery by the hybrid inverter), and stops at 80%, or if the system sees I'm importing from the grid (typically as someone has started cooking, a dishwasher has gone to the heating part of the cycle, etc). It's working really well for me, although of course requires a certain skillset