Solar install as part of ECO4 grant

NedS

Hi all,

We are looking at a potential solar install as part of an ECO4 grant (also including ASHP and added insulation). I have a separate thread on the heat pumps forum for that side, but wanted to learn more about the solar side here.

We have been quoted (very limited details so far) for 8 x 434W panels and a 3.6kW inverter.

I see 3.6kW inverters (sometimes 3.68kW) appear quite common - is this related to the maximum they can install without additional permissions from the grid or something? I'd like to know more about this if possible.

Besides asking the brands of panels and inverter, I'm also going to try to push them to up it to 10 panels so I can get 4.3kWp as I've read about the benefits of over-sizing relative to the inverter, and panels seem dead cheap atm.

As it's on a grant, they do not offer much else, so batteries are out as are things like immersion diverters to drive an immersion heater for hot water. That said, it's probably more efficient to heat water in summer from the ASHP and have any solar drive that due to multiplying effect of the COP efficiency.

The roof is large south facing in the south of the UK. the website https://re.jrc.ec.europa.eu/pvg_tools/en/  suggests 3500-3600kWh generation at my location, and I understand 3000-3600kWh/year is not unreasonable.

Other than trying to get them to increase to 10 panels, what else should I be looking for?

What about monitoring (I'm a numbers geek so love this stuff)? What minimal monitoring might we expect an installation to provide, and what additional monitoring might be available at reasonable cost?

What about tariffs and rates for exporting excess generation back to the grid? We are currently with OVO on their standard flat rate and I've not even begun to look at export rates with different suppliers. Any recommendations for suppliers and tariffs would be greatly appreciated.

Thanks in advance for any help / advice.

Spies

If its grant based you'll likely not get any say over what equipment is used unfortunately and there won't be the ability to pay extra to get what you want. 

Netexporter

I'm in a similar situation. You can ask for a quote for betterment but I found the quote I got was far too high, bearing in mind they have the people/scaffolding etc already there. I'm just going to take the free offering, for now, and up grade at a later date when I will also get batteries installed.

QrizB

NedS said:

What about monitoring (I'm a numbers geek so love this stuff)? What minimal monitoring might we expect an installation to provide, and what additional monitoring might be available at reasonable cost?

Most current models of inverters have wifi (either built-in or as an extra-cost add-on) that will either offer a local website or connect via your broadband to the manufacturer's servers. From there you can get general performance data.

NedS said:

What about tariffs and rates for exporting excess generation back to the grid? We are currently with OVO on their standard flat rate and I've not even begun to look at export rates with different suppliers. Any recommendations for suppliers and tariffs would be greatly appreciated.

As far as I can tell, the supplier with the biggest range of solar-friendly tariffs is Octopus (I could be wrong).

You can see their matrix of tariffs here:

https://octopus.energy/help-and-faqs/articles/which-export-tariff-can-i-combine-with-my-import-tariff/

And most of Octopus's import tariffs can be seen here:

https://energy-stats.uk/

NedS

QrizB said:

NedS said:

What about tariffs and rates for exporting excess generation back to the grid? We are currently with OVO on their standard flat rate and I've not even begun to look at export rates with different suppliers. Any recommendations for suppliers and tariffs would be greatly appreciated.

As far as I can tell, the supplier with the biggest range of solar-friendly tariffs is Octopus (I could be wrong).

You can see their matrix of tariffs here:

https://octopus.energy/help-and-faqs/articles/which-export-tariff-can-i-combine-with-my-import-tariff/

And most of Octopus's import tariffs can be seen here:

https://energy-stats.uk/

Thanks - that's brilliant.

I'm looking at Agile combined with fixed outgoing (15p export), and that looks mighty attractive. We do cook with an electric oven at peak time (4-7pm), but the average rates during this time are not much higher than our current standard flexible rate of 28.7p, but the rest of the day is significantly cheaper. With a constantly on ASHP and being in all day, I think this tariff could work well for us, plus the 15p SEG export rate is almost matching the average import rate from 10-4pm, which eliminates a lot of the downside of not being able to use all you generate in summer.

We don't have that much usage we can move to cheap times, other than heating the hot water tank 1h daily, and putting the washing machine on at cheap times. I do heat an outside office with an electric radiator, which will obviously be significantly cheaper to leave on overnight during winter or have come on for a few of the cheapest hours on a timer. I'm sure we could knock back the ASHP for 3 hours 4-7pm which would also help.

QrizB

If you do switch to Octopus, be sure to get a referral code from friends or family so you both benefit from the £50 bribe.

Screwdriva

I know a few who have had ECO4 installations. Here are a few common themes:

1) Efficient and customer driven are two words I would not use to describe the people running these schemes. 

2) Almost all use JA Solar panels and Solis inverters, not ideal, but hey, it's "free". Worth asking for bird netting too. 

3) Flat roof/ on roof systems only. No In roof mounting. 

4) Some ECO4 installers will survey in person but the results are practically worthless, as the # of panels/ size of system may change multiple times due to the bureaucracy of the system, especially if you ask for more panels.

If you want maximum number of panels that can possibly fit on your roof, which is highly recommended, you must insist on this in writing in every correspondence, and offer to pay for the additional panels if you have to. They won't welcome this level of persistence, but in the end, it has almost always led to a better outcome.  

NedS

I now have a little more info from the installer.

Panels are Trina 435W and the inverter is a Growatt 3.6kW.

They have specified 8 panels (3.48kW). They are going to see if they can stretch to 10, and I'm considering paying for the additional two panels if they won't (they have confirmed I can do this). Is it worth paying for two extra panels on a south facing roof? (~28 degree roof at -2 azimuth, south facing). I'm assuming yes based on:

https://www.youtube.com/watch?v=5y2dJ8S6zDU

Screwdriva

NedS said:

Is it worth paying for two extra panels on a south facing roof?

The answer to your question is a definite Yes. I have always advised recipients of the grant to offer to pay a reasonable sum to maximize panel coverage. Those who have agreed typically ask for upto £500 for 2 additional panels.

pete-20-11

I assume it will cause clipping on sunny summer days? Inverter won't be able to "invert" from 10 panels at their max wattage as it'll be more than the inverter can cope with?

Obviously at other times of the year, when panels won't get to their max output as much, then the extra panels will mean extra generation.

So a bit of a balancing act, but hopefully worth it overall. 

Plus of there's any shading on some of the panels, or if some of them are in different directions, then the clipping might not be as much. 

Screwdriva

It’s very unlikely that the system will clip with 10 panels for more than a handfull of hours in the year, if that.