Solar PV - economics?

[CubanPete]

What about Tesla tiles?

[djglover]

If you have an EV you can sometimes charge at home and octopus agile outgoing the payback is good.

I expect to generate 4000 kWh / yr from mine

1000 exported at 10p = £100
2000 consumed in house saving 17p = £340
1000 consumed by car saving 30p = £300

For a £5k install that’s 6.75 years to return, so not bad IMO

Edited by djglover on Tuesday 8th June 09:00

[Chris Type R]

Tlandcruiser said:

rustyuk said:

What about breakdowns? In 10 years the kit will need replacing.

The solar panels being installed for my house come with a 20 year warranty and a 10 year warranty on the inverter. Inverter prices have came down in price a lot over the years too.

And in some cases, you can even justify replacing the invertor / fit optimisers to boost the installation output.

[Condi]

djglover said:

If you have an EV you can sometimes charge at home and octopus agile outgoing the payback is good.

I expect to generate 4000 kWh / yr from mine

1000 exported at 10p = £100
2000 consumed in house saving 17p = £340
1000 consumed by car saving 30p = £300

For a £5k install that’s 6.75 years to return, so not bad IMO

Is that all coming from solar power, or are you buying from the grid?

Also, why is the house consumption saving 17p and yet the car saving 30p - your overnight charging rates for the car will be cheaper than the daytime rates for the house, no? O/N are like 6p/kwh or something.

[Mr Whippy]

Cheib said:

Roof mounted with this house wouldn’t work…it’s a period house and roof has wrong orientation. Don’t understand output being lower at all (assuming no shade), I read somewhere about one of the advantages of ground mounted is that the panels can be mounted at the optimum angle and also tilted so they perform better in winter….that may all be rubbish though !

Ground must be perfect.

I'd assume that frames can/are made that have cranks or just settings (like an ironing board) so you can angle them up/down too, so summer to winter you can angle them down to optimise the electricity generated.

[Saleen836]

djglover said:

If you have an EV you can sometimes charge at home and octopus agile outgoing the payback is good.

I expect to generate 4000 kWh / yr from mine

1000 exported at 10p = £100
2000 consumed in house saving 17p = £340
1000 consumed by car saving 30p = £300

For a £5k install that’s 6.75 years to return, so not bad IMO

Edited by djglover on Tuesday 8th June 09:00

Who will you getting 10p per kwh exported from?

[djglover]

Agile Octopus averages out at 10p, lower off peak but 16p after 4pm

and yes 30p is overcooked, of course sorry. Looking at 8 year payback

[gmaz]

Saleen836 said:

Who will you getting 10p per kwh exported from?

https://octopus.energy/outgoing/

I think 10p is a bit optimistic, when the fixed price is 5.5p

[djglover]

My latest statement averaged 8.94p / kWh

[Condi]

djglover said:

My latest statement averaged 8.94p / kWh

Is that just a flat average, or does it take into account your usage?

IE, 8.9p sounds great, but if you use 50% of your daily power between 4pm and 8pm then YOUR cost is going to average higher than 8.9p.

[djglover]

Those are the half hour prices there, so if you export at 4:30 pm its 16p kWh

My weighted average was 8.9p. Its usually a bit higher than show on that graph, thats for today

[Evanivitch]

Condi said:

Is that just a flat average, or does it take into account your usage?

IE, 8.9p sounds great, but if you use 50% of your daily power between 4pm and 8pm then YOUR cost is going to average higher than 8.9p.

That's the average across his bill usage. I'm on GO, and despite limited mileage in the car I still average 10p/kWh across nearly 6 months.

[Condi]

djglover said:

Those are the half hour prices there, so if you export at 4:30 pm its 16p kWh

My weighted average was 8.9p. Its usually a bit higher than show on that graph, thats for today

I see, thanks. Wind a bit higher than it has been this evening, hence lower prices.

[anonymous-user]

My pv array with 5kw inverter was installed on Wednesday. Cost was a few pennies short of £6k.

Haven’t had a full day of sunshine yet but am getting around 20kwh each day, it peaked at 4.99kwh on thursday when the sun came out around noon so I’m optimistic that I can do much better than 20kwh in a day as its been very spikey with the cloud cover.

As I am using pretty much all of the available output thats 20 x 18p = £3.60 a day saving, £1314 per annum. I appreciate that pv output will fall either side of this time of year so hopefully £1k a year would be nice.

Tesla battery due to be fitted early July which will improve savings (albeit the battery is a chunky nearly £9k).

Anderson car charger has arrived and is waiting to be fitted. Next decision is which EV for the school bus duties.

I will update when I have more, better data.

[Paul Drawmer]

soofsayer said:

My pv array with 5kw inverter was installed on Wednesday. Cost was a few pennies short of £6k.

Haven’t had a full day of sunshine yet but am getting around 20kwh each day, it peaked at 4.99kwh on thursday when the sun came out around noon so I’m optimistic that I can do much better than 20kwh in a day as its been very spikey with the cloud cover.

As I am using pretty much all of the available output thats 20 x 18p = £3.60 a day saving, £1314 per annum. I appreciate that pv output will fall either side of this time of year so hopefully £1k a year would be nice.

Tesla battery due to be fitted early July which will improve savings (albeit the battery is a chunky nearly £9k).

Anderson car charger has arrived and is waiting to be fitted. Next decision is which EV for the school bus duties.

I will update when I have more, better data.

I've had PV installed for over 10 years and kept monthly figures for that time.
Your short term figures are wildly optimistic.

[loskie]

2Btoo said:

£12k in, around £4.5k in my pocket after 14 years.

Leaving aside all discussions about risk, that was not a good investment.

It's not been a good investment for you because the way YOU managed it. Had you had it for the FULL 25 years then it would have been good. This was the basis that you would buy it on. Any solar PV sold back in 2010 (or thereabouts) these were the sums. It really wasn't hard to understand.

So what you did was like buying shares and selling them a week later when the price had plummeted NOT holding them for the longer term and benefitting from both dividends and hopeful upturn in price.

I installed 3.6kw of panels in 2010 or 11 and they have to date made 29500 units at the higher rate FIT.

[GAVGOLF]

I’m afraid your assumptions are wrong.

Roughly 75% of your generator Will come March to September.
Over winter you will barely generate

You cannot use the average for now (summer) and apply it as a daily number all year.

soofsayer said:

My pv array with 5kw inverter was installed on Wednesday. Cost was a few pennies short of £6k.

Haven’t had a full day of sunshine yet but am getting around 20kwh each day, it peaked at 4.99kwh on thursday when the sun came out around noon so I’m optimistic that I can do much better than 20kwh in a day as its been very spikey with the cloud cover.

As I am using pretty much all of the available output thats 20 x 18p = £3.60 a day saving, £1314 per annum. I appreciate that pv output will fall either side of this time of year so hopefully £1k a year would be nice.

Tesla battery due to be fitted early July which will improve savings (albeit the battery is a chunky nearly £9k).

Anderson car charger has arrived and is waiting to be fitted. Next decision is which EV for the school bus duties.

I will update when I have more, better data.

[Jambo85]

My 3.6 kWp east/west array occasionally delivers more than 20kWh in a day so I expect you will see over 30kWh on a good day particularly if your array faces south, but you must realise it’s the longest day of the year tomorrow, what you’re getting just now is nowhere near representative of the average, sadly.

[rxe]

Here is ours for last year:



That’s a 4 kW system.

[anonymous-user]

Jambo85 said:

My 3.6 kWp east/west array occasionally delivers more than 20kWh in a day so I expect you will see over 30kWh on a good day particularly if your array faces south, but you must realise it’s the longest day of the year tomorrow, what you’re getting just now is nowhere near representative of the average, sadly.

Yes you’re all correct but I’m allowed to dream. Man maths!