Solar Panels?

[KTF]

OutInTheShed said:

This is the grid operators wanting exports limited, not the retailers?

I think some of the tariffs today can encourage people to dump the contents of a battery just before it becomes cheap to recharge the battery.

As more people get batteries, the tariffs will have to be tailored to suit the DNO as well as the customer and the retailer.

My DNO has given me an export limit of 5kW.

Doesn’t matter if it comes from the roof, the batteries or both. Thats just the max you can export.

The inverter is capped at 5kW AC out anyway so no point getting a bigger one as can’t export more.

[KTF]

Well I am back on the solar panel fence again.

I simply can’t get into add up from a financial point of view and if prices drop further over time it goes more to the right.

As/when I get an EV I will revisit it but at the moment it doesn’t sit ‘right’ with me for it to make sense.

[McGee_22]

KTF said:

Well I am back on the solar panel fence again.

I simply can’t get into add up from a financial point of view and if prices drop further over time it goes more to the right.

As/when I get an EV I will revisit it but at the moment it doesn’t sit ‘right’ with me for it to make sense.

After just having invested in some I would rightly acknowledge your caution. I would suggest you get the figures of how much electricity you use a year, and more critically through December to February, as well as how much it costs you to heat hot water from say April to October.

Realistically the electrical energy you use between December and February you will always pay for. March and November you may make enough power to cover yourself depending upon the size of your installation. Again depending on the size of your installation you should make enough power from April to October so you should be able to turn off GCH if you currently use that for hot water.

You need to save the power you make each day so batteries are essential to get through the night, but to be able to get around the clock day to day without taking from the grid you need to factor in evening and night time use into your battery installation capacity, including such things as ovens, kettles and of course washing machines, dishwashers and the power hoover that is a tumble drier.

Once you have a average daytime figure for spring and autumn electricity consumption factoring in all that (^^^^^) you can estimate the size of the battery, and from that the size of system to charge it.

I wish it had been done for me as I now have an oversized array which even in March on a half sunny day fully charges my battery, but being oversized it takes its own sweet time getting going through December to February and the battery barely charges whereas my neighbours smaller system wakes up and gets going. His isn't perfect though as his battery is too small but that is relatively simple to fix.

[Cheib]

McGee_22 said:

I wish it had been done for me as I now have an oversized array which even in March on a half sunny day fully charges my battery, but being oversized it takes its own sweet time getting going through December to February and the battery barely charges whereas my neighbours smaller system wakes up and gets going. His isn't perfect though as his battery is too small but that is relatively simple to fix.

What do you mean about it being oversized taking its time ?

[McGee_22]

Cheib said:

What do you mean about it being oversized taking its time ?

I have 14 panels on two arrays feeding into 8kw max inverter. My neighbour has 10 panels on one array feeding into a 6.6kw max inverter. The panels, wires, roofs and almost everything are identical - the inverters are the same make with the same specification apart from the capacity - they were installed by the same company a couple of months apart.

On a shady winter day he will start generating before I do and finish generating later - it is supposedly something to do with the combination of my two seven panel arrays each being smaller than his one 10 panel one and the point at which the larger inverter starts generating from the lower input from each array. Obviously on a sunny day I generate a lot more power by virtue of the 40% more panels.

I suspect if I had one array of ten I would have similar length of day characteristics, but the system has been tested to the Nth degree and it is just a quirk of two smaller arrays feeding into a larger capacity inverter that puts me to a disadvantage in the winter months.

[silentbrown]

McGee_22 said:

On a shady winter day he will start generating before I do and finish generating later

The key figure is the inverter's startup voltage. Mine is 150V (Givenergy 3.6 Hybrid)

With seven panels, you'd need ~21V per panel output before it can start. With ten panels, you only need 15V.

However, it's usually largely irrelevant, because when a panel is generating under 30V there's only a tiny dribble of power being generated. Usually single-digit numbers of watts for the entire array.

Today my array started generating 1 watt at 6:15 AM. By 7:35 the string voltage had jumped to ~400V, and it was making a whopping 38W...

[OutInTheShed]

McGee_22 said:

I have 14 panels on two arrays feeding into 8kw max inverter. My neighbour has 10 panels on one array feeding into a 6.6kw max inverter. The panels, wires, roofs and almost everything are identical - the inverters are the same make with the same specification apart from the capacity - they were installed by the same company a couple of months apart.

On a shady winter day he will start generating before I do and finish generating later - it is supposedly something to do with the combination of my two seven panel arrays each being smaller than his one 10 panel one and the point at which the larger inverter starts generating from the lower input from each array. Obviously on a sunny day I generate a lot more power by virtue of the 40% more panels.

I suspect if I had one array of ten I would have similar length of day characteristics, but the system has been tested to the Nth degree and it is just a quirk of two smaller arrays feeding into a larger capacity inverter that puts me to a disadvantage in the winter months.

Sounds like a matter of the inverter not being well matched to 7-panel strings.
The 3.6kW system I keep an eye on has two strings, each running close to 200V.
It's done 14.2kWh so far today

That 3.6kW system would, with adequate batteries, have provided about 45% of my electricity in Jan and Feb and about 75% in March with some export. That's rough working-out based on about 12kWh per day.

It's this system in Newquay.
http://www.newquayweather.com/wxsolarpv.php?date=2...
Note that the system has been in place for about 12 years and already both strings of panels have been replaced!

The two strings of panels are different brands, one is 5 panels, the other is 7, so clearly not all panels are the same number of cells in series.

[Ken Figenus]

This is interesting as I have an old 3.5kW system and a new 4.1kW system recently added with 10kWh batteries.

Some of the posts refer to needing an EV to benefit (which I absolutely believed) but the irony is that current tariffs want you to be a mini power station! You charge your car and house batteries off peak for 9p kW and then in the day you sell the PV power you generate for 16p - this just on my straightforward tariff - more complex ones are available!

You are maxing your batteries for profit. That's not why I got PV. I like being off grid in the City (at times) and nailing a near 600bhp EV powered by the sun, man... Also you will hammer those batteries that have a limited use warranty and limited life. Complex PL calcs...

So, I'm not doing it.

Got 30kW in the car over 2 days - I love that - and no grid import for the house... That's why I bought it. I'm absolutely definitely quid's in too but a bit man maths on it all

[thecopster]

So I’ll start by saying i don’t really know anything about solar!

My situation is fairly typical though:

-EV car
-4 bed house with 3 teenagers so high consumption ~1200kwh per month
-gas central heating

I asked my energy supplier Octopus for a quote and they came back with this:





I have no idea if it’s what I need/any good!

I am based in Bristol so anyone who has had a local install done in my area I would be grateful to receive recommendations!

Thanks

[McGee_22]

silentbrown said:

McGee_22 said:

On a shady winter day he will start generating before I do and finish generating later

The key figure is the inverter's startup voltage. Mine is 150V (Givenergy 3.6 Hybrid)

With seven panels, you'd need ~21V per panel output before it can start. With ten panels, you only need 15V.

However, it's usually largely irrelevant, because when a panel is generating under 30V there's only a tiny dribble of power being generated. Usually single-digit numbers of watts for the entire array.

Today my array started generating 1 watt at 6:15 AM. By 7:35 the string voltage had jumped to ~400V, and it was making a whopping 38W...

Thank you for this explanation - I think you've nailed the issue with the start up voltage vs voltage per panel. Both our inverters are Growatt with the same 150v start up and 120v to 550v range once running.

Another odd thing I noticed about solar panel output was how much clouds make a difference - I don't mean in the obvious way as in direct conflict of the panels but as a reflective sheet. Once the sun starts setting in the South West away from the South East array there is more solar power being generated if there are clouds in the South East to reflect off rather than a clear blue sky there.

There are lots of anomalies that can affect solar generation and the knowledge is out there - but seemingly not in the minds of the moron surveyors they send out to get you to sign up.

[the-norseman]

thecopster said:

So I’ll start by saying i don’t really know anything about solar!

My situation is fairly typical though:

-EV car
-4 bed house with 3 teenagers so high consumption ~1200kwh per month
-gas central heating

I asked my energy supplier Octopus for a quote and they came back with this:





I have no idea if it’s what I need/any good!

I am based in Bristol so anyone who has had a local install done in my area I would be grateful to receive recommendations!

Thanks

I've just had a quote from eon next for about £9.8k for a set up including a 5.1 kwh battery offered on 3 years 0%

3 storey house, rear gets the sun very strong in the afternoon. tempted as we are spending a fortune on electric to be honest.

[DonkeyApple]

the-norseman said:

I've just had a quote from eon next for about £9.8k for a set up including a 5.1 kwh battery offered on 3 years 0%

3 storey house, rear gets the sun very strong in the afternoon. tempted as we are spending a fortune on electric to be honest.

The trouble with 0% is that it is a marketing fabrication to hide the funding cost in the asking. Implicit funding always being dearer than explicit for the solvent.

[dmsims]

[soupdragon1]

DonkeyApple said:

the-norseman said:

I've just had a quote from eon next for about £9.8k for a set up including a 5.1 kwh battery offered on 3 years 0%

3 storey house, rear gets the sun very strong in the afternoon. tempted as we are spending a fortune on electric to be honest.

The trouble with 0% is that it is a marketing fabrication to hide the funding cost in the asking. Implicit funding always being dearer than explicit for the solvent.

Absolutely.

Its quite possible to get a 'free' solar install, just takes a bit of work with a calculator and going onto a website to predict usage.

Step 1 - get the best quote you can find as a cash purchase
Step 2 - look at your projected pre and post solar electricity bill
Step 3 - the variance between pre and post becomes your monthly payment for a typical bank loan

So if your average monthly electric bill goes from £200 to £50, then get a bank loan for the amount of the install, and tweak it so that the monthly payment is £150

Doing it that way, your monthly bills remain the same, £200 (albeit, with large seasonal variations) and after a number of years, the bank loan is paid and you own all the equipment and are now into net savings territory. Magic

I just bought mine and paid straight up but if we were still in a low interest rate environment, I might well have taken the above approach. If you don't have the funds to hand straight away, its a possible solution without impacting your overall bills. Basically, its a free solar install

[soupdragon1]

dmsims said:

Thats awesome.

Much better value if you just employ a solar spark and buy the stuff yourself. You have to pay 20% VAT when DIY, however, as you've shown, still works out fantastic value.

I went with a company install, and for 14 panels, hybrid inverter, cost me £5.4k - no battery.

When the spark arrived, he wasn't an employee, he was a subcontractor. So he's coming back tomorrow to install a Zappi charger for me. £1.2k going with the company but I bought the Zappi for £525 online and he's putting it in for £200, so £725 instead of £1,200. Quite a lot of margin!

[Mr Penguin]

Where do you buy the panels and batteries etc if you buy them yourself?

[KTF]

Are you planning to try to export from the self install as you won’t have the certification?

Can see why people do it for self consumption only.

[soupdragon1]

Mr Penguin said:

Where do you buy the panels and batteries etc if you buy them yourself?

Trade spark seems to be a popular site.

https://www.tradesparky.com/solarsparky/solar-pane...

If not tradesparky, I might buy my batteries from here:

https://www.fogstar.co.uk/collections/solar-batter...

£2.5k for a 15kwh battery is great value but I doubt I would be able to get it into my loft, due to the enormous weight. So probably go for smaller batteries and join them up.

[dmsims]

It wasn't my install but if you want to export Octopus are doing a non MCS (waste of space) scheme

KTF said:

Are you planning to try to export from the self install as you won’t have the certification?

Can see why people do it for self consumption only.

[Mr Penguin]

KTF said:

Are you planning to try to export from the self install as you won’t have the certification?

Can see why people do it for self consumption only.

Just looking into costs of different ways to do it to see which makes more sense. I think as long as the electrician who wires it up is certified then it is fine even if I install the panels myself or hire a roofer to do that part for me.