Solar PV Quotes

Martyn1981

Just to clear up any confusion. Some of the terms, sizes and calcs:-

The system size registered on the MCS certificate and with the FiT provider is the total of all the PV panels, so 16 250Wp panels would be registered as a 4,000Wp system.

If the inverter caps at 3,680W then the DNO can be notified afterwards for it to be recorded with them. If the PV system is greater than 3,680Wp and the inverter doesn't cap at 3.68kW then the DNO needs prior notification, and their approval before the system is commissioned.

Previously there was a 0-4kWp FiT rate, and an over 4kWp to 10kWp FiT rate (plus larger brackets too). Now the two smaller brackets have been combined into a 0-10kWp FiT banding.

FiT payments are made on the generation of the system, not the size of the system.

A south facing 4kWp system may generate somewhere between 3,600kWh and 4,400kWh pa (on average, and of course there will be exceptions). An East, West or E/W 4kWp system may generate around 3,200kWh pa.

In the above examples both systems get paid depending on their actual generation, and as recorded on the TGM (total generation meter) which is placed between the inverter and the consumer unit.

So as an example, with a 4p FiT and 5.2p export rate, if the 4kWp south facing system generated 4,000kWh's then it would receive 4,000 x 4p for FiT's and 2,000 x 5.2p for export. The E, W, E/W systems generating around 3,200kWh's would be paid 3,200 x 4p, and 1,600 x 5.2p.

If the systems break and generate nothing, then they get nothing. So the subsidy is paid only on actual realworld generation.

Edit - I think this method of support/subsidy is pretty good. The contracts for difference (CfD's) for the big schemes like off-shore wind and nuclear are similar in that a pre-arranged figure is agreed at auction for the generation, eg £100/MWh, so when the generator sells a MWh for say £50, they get a top up of £50, if they sell at £80 they get a £20 top up, if they sell at £120 (during an evening peak perhaps) they have to pay £20 back into the subsidy pot.

This means that no subsidies are given towards the construction of the projects, and any project that fails to work, or underperforms, gets paid less subsidy since it only gets £'s when it supplies MWh's.

ASavvyBuyer

Zarch wrote: »

Thanks Eric, but super confused now.

Sorry for taking this thread sightly off-topic, but I thought that the current FIT calculation was 100% of size of array x 4p (current generation tariff) + assumed/estimate of 50% of generation x 5p (current export tariff)

So they are derived calculations than actual ones from a generation meter?



http://www.energysavingtrust.org.uk/scotland/grants-loans/renewables/feed-tariffs

Who makes the decision whether the FIT comes of derived 50% figures or mandates the installation of a smart meter?

What is happening right now with current installs?

So for the OP 6kWh system I thought it would be 6000 x 4p (£240) + 3000 x 5p (£150) = £390 per year?

Or could it be 3.68kWh (based on the inverter max)?
3680 x 4p (£147) + 3000 x 5p (£92) = £239 per year?

:huh:

You will get paid each quarter for how much your system actually generates, based on the FIT rate and 50% of that for Export.
Just because you have 6kWp of panels, does not mean you will actually generate 6,000kWh per year.
It depends on the weather and how sunny it is.
To work out how much your system is likely to generate take a look at PVGIS.

Zarch

ASavvyBuyer wrote: »

You will get paid each quarter for how much your system actually generates, based on the FIT rate and 50% of that for Export.
Just because you have 6kWp of panels, does not mean you will actually generate 6,000kWh per year.
It depends on the weather and how sunny it is.
To work out how much your system is likely to generate take a look at PVGIS.

ahhh, penny drops. :rotfl:

Nick6659

Hi Martin, where do your FIT numbers come from please?

Martyn1981

Nick6659 wrote: »

Hi Martin, where do your FIT numbers come from please?

Hi, they were just simplified numbers, the exact numbers can be found here and are 3.93p/kWh FiT and 5.24p/kWh export.

Zarch

So just to be finally clear on OP Nick's choices here, mainly for my benefit. :j

Despite being able to put 6kWh of panels on the roof the installer suggests a 3.68 inverter over a 5.00 one based on saving around £400 at install time.

With that extra £400 cost either coming from two possible choices
a) upgrading the inverter from 3.68 and 5.00 and also the £220 G59 DNO application
or
b) A limitation device / G59 fast track and inverter upgrade.

So for clarity. Having a 3.68 inverter below 6kWh worth of panels caps/limits generation and export potential at 3.68.

But what the installer is saying is that those 'good' days likely only amount to about £25 max extra FIT per year especially considering his multi aspect installation.

So you're talking 16 years to pay for those upgrades.

Is that about the sum of it?

pinnks

Sort of...

I read this to say that with 6kWp of panels the OP has 3 main choices:

1. just stick in a 3.68kW inverter and live with the (potentially) annoying consequences of that decision when you know you are generating enough to run the dishwasher and washing machine at the same time but the system is capped at 3.68kW. You would also be losing FiT, though at a net 7p or so per kWh (generation plus export) that would not be the end of the world. On the plus side of course your generation from 6kWp of panels would be higher in the winter months than from 3.68kWp, so what you lose in the summer you gain in the winter...

2. Apply G59 and wait a few weeks for the decision, pay £220 for that decision and £200 for a larger inverter. If the DNO plays silly bxxxers with the application withdraw and chose a different route. Benefits are less capping on production - you get what you generate - maxing out on FiTs and being satisfied that your hungry appliances can be run at zero cost for more days in a year than with a capped system. No gains or losses with the seasons as the system just generates what it can. But you do get the full benefits of going large in that you max out on the kW at any given time of the day.

3. Go with the limiter option at ?? cost. Appears to be cheaper than G59 application and saves the £200 on the larger inverter but will have a cost in terms of the limiter. The advantage over 1.is that you still max out on the FiT and own consumption but presumably still lose out on the export as it surely won't be based on 50% of generation if the system is throttled back?

Personally I would explore option 2 and possibly 3 as I have to ask why one would max out the panels only to go small on the inverter unless the only consideration is trying to keep the kW of available power high and constant throughout the day. But perhaps it's just me???

pinnks

Just thought I would add some numbers from what is admittedly a super July.

So far (up to yesterday, 22 July):
Generated 549kWh
Exported 342kWh (62%)
Diverted 70kWh to immersion tank
Imported 67kWh
Household use 204Kwh (excluding diverted)

On average over the main summer months (June, July and August) the ratios are quite similar with about 60% exported from my total 5.25kWp un-capped systems.

Nick6659

Pinks - would a battery change your thinking?

pinnks

If batteries were economically viable (in my case for retro-fit of course) I would have the installers outside right now. Trouble is at current prices and without some sort of subsidy it would take me getting on for 40 years to recoup the cost of a battery!

I import about 1,600kWh per year (about £200). If I assume that I could cover, say, 1,200 of that from the battery (about £150) at, what, £4,000 installed, it would take over 25 years to break even, ignoring inflation and the fact that I would probably need to replace the battery after 10 to 15 years, hence my guess at about 40 years.