S2D2

If you have an existing duct for cable runs the CT can be extended with cat6 up to 100m usually. It would save the DC -> AC -> DC -> AC losses of a second inverter for the battery.

It's been a good end to the month for PV, I've generated around 115kWh this month, 10% ahead of the PVGIS estimates.

It's more revealing as a 32 bit binary: 11111111111111111111111111111110 I.e. one short of the max value. Or some weird little endian signed integer for no reason. From a software perspective, here be monsters.

From what I've seen this issue mostly applies to 90's houses where the common build up is block and beam, 50mm EPS, floating chipboard floor. Worse, like mine, big gaps are often left in the EPS to run ground floor heating pipes... So the insulation is okay (read: better than nothing), but there's a bunch of space under the beam and block that won't be on show that it feels like there should be a solution to add a boatload of insulation to. The lack of a DPM is a key limitation though as ground gases can't be ignored.

Yes, still no luck for retrofitting unfortunately, from the technical docs:

In my opinion this is the most reliable method for comparison, ours came out at something like 4.1 kWh/hdd. Remember to include the electricity consumption which is lost into the house as heat too. Adjust if you have any CoP input. Easy enough to factor in exposed perimeter giving an average U value which seems to me the best metric for direct comparison. You don't even need to plot it, just take your annual usage and divide by the total HDD for the year, see: https://www.degreedays.net/. Plotting daily does allow you to filter out the summer days which will skew the regression fit quite significantly once you factor in electric consumption. Mine came out at 0.66W/m2K if I remember rightly, plenty room for improvement but it is a 90's house.

Get some more quotes, that's ridiculous for a 4kWp install. Take 40% off and it would be reasonable. Less if that's switching for a hybrid inverter, it's not clear from the quote.

Sorry OP I can't help with the lights, but this requirement got me curious. Can anyone shed light on why this is required? It's a high base load to rely on and the (vastly more expensive) Eddi doesn't seem to mention this requirement?

The airflow through reasonably well packed beads will be vastly reduced relative to outside air due to viscous drag etc. So I would neither rely on it for ventilation (though indeed it is not airtight) nor worry about it for insulation. I don't have any figures for you but it would be not too much effort to model.

Thanks both, unfortunately not enough room in the CU but it was trunked neatly at ceiling level so could be a lot worse.

As a point of reference, the standard install practice for my Solax hybrid inverter's CT clamp is to extend it (ours was done with CAT6 internally, the manual does not specify) and the install manual says not to go over 100m, so plenty of room to play with. Ours runs ~10m with no issues.

This does seem high, but perhaps it's just a big one or some things were added to be frozen? The sample size is small so could be affected by something like that. I don't monitor mine directly but smart meter data shows it has a background usage of around 365kWh/year. Add a bit for things being put in, door opening etc. Also if you're using a smart plug to monitor I found mine on a dehumidifier was overestimating by 20%, which may go part of the way to explaining it.

Here it is, just input your postcode then the other parameters, it lets you play with different configurations etc. and most people find it lines up with real world performance reasonably well: https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP I don't have a basic guide reference, I think you understand the fundamentals from the spreadsheet but the forum will be happy to answer any specific questions I'm sure. If you have a smart meter at your current property, you can get into some proper analysis of what you might self use in the new house with respect to plug in electric, see my other thread: I have a system installed now and have started logging data so can share more on real usage soon, but others have posted various data in this forum topic before. The key takeaway is it's massively usage dependent, every household is different and will self-use different amounts. You can change usage patterns to address this, but solar is very unpredictable. A battery helps smooth this out but they are very expensive at the moment. We installed a small one (3kWh) as we don't consume enough to go down the Octopus Go/E7 route. For the shading, it will affect you differently throughout the year. Whilst the average for a 2m dormer might shade 1.7m, in winter with the sun at 15 degrees it might shade more like 7.5m. I believe PVGIS can model this to show the overall effect, but I've never used it for this. This may push you towards all the panels on the west side, or it may not be an issue. Also check vertical mounted panels on the South wall, depending on the space you have there and view on aesthetics. As you haven't tiled yet, in built panels will be "cheaper" for you as you will save on tiles, so probably stick as many as you can up there, just consider the shading.

Be careful assuming self use will be so high, if the hot water and car charging are set up as a divert that will greatly help self use but for heating (unless also divert with some logic if you're not installing a heat pump?) and plug in electric (assuming this is house load?) your generation and consumption are unlikely to line up. I found self use for house load was as low as 30% using PVGIS and smart meter data. With an E/W split you definitely need to be using PVGIS data as generation will be a lot lower, I'm unsure if this is already factored in? If that dormer is on the East roof am I right in thinking it's towards the South end of the roof? That would shade panels significantly on the larger portion of the roof so would need careful consideration.

Yes, this is the case. I was confused as to why the location of the CT clamp mattered along the cable but have finally spoken to the electrician and the actual reason is that he's not happy to fit a connecting block to the tails within a stud wall and wants it to remain accessible, hence they want to do it in the meter box and run the electric cable from there. Ugly cable across the garage it is then.

I've used these in a traditional loft space, if you apply attention to detail with the sealant covering all cable entries etc they give an airtight seal. Remember to seal the cable with extra slack so the downlight can still be pulled downwards if required. Unsure on your roof structure though as you should insulate above them.

I have the same setup, B&B floors with 50mm polystyrene, apart from one room with 50mm PIR instead. Probably 600+mm void underneath the floor though. The only sensible thing I've seen is the little spray foam robot you can send under which retains a ventilation gap, but that turned out to be prohibitively expensive. Watching with interest.

Thanks both, I'm no closer to clarification unfortunately, they're coming back next week though. To expand a little it's just a data connection I'm talking about, not power. Here's the installation manual: https://kb.solaxpower.com/image/68499e58090d4aafa0fb6d0545d4f2c1/2022-11-14/aceecfb2d55c951ce2334351692f3825.pdf The meter Solax sell comes with a CT clamp too, so it seems both are required not either. I had assumed the meter might have it built in: https://www.itstechnologies.shop/collections/solax-batteries/products/solax-chint-single-phase-ct-energy-meter And based on the installation manual it seems it can go anywhere between the household meter and the house load (consumer unit). No idea what he was on about with having to run a cable to the smart meter then.

Make sure the vents are taped over or something if the extractor has not been reconnected as even without a fan stack ventilation will be pushing hot, humid air up into the loft space. Rather typically when I went up to fit the new felt lap vents almost all of the condensation has blown off and dried up. We have had a fair bit more wind the last 24 hours but I'll probably have to wait until next year to see if the balance has been tipped back. A good airflow coming through the new vents though so they must be helping.

I've used these to good effect. However I topped up the loft insulation and the problem has tipped back to condensation like yours, so I've just taken delivery of a load more to try and get it sorted again. I only put 15 in first time. What has happened to the extractor vent that was connected to this pipe, is it now exiting directly to the loft?

Is the noise an issue or do you have them placed out of the way? I'm thinking about PV divert and have been looking at posts on these with interest. Useful info thanks @TerryE, trying to think how well this will work in the 90's house you mention at the end (but mine!). High thermal capacity still but larger temperature swings needed due to the much higher energy input.

Quick question on something my PV installer mentioned that isn't clear from the inverter installation manual: Is a hybrid inverter plugged directly in to the electric smart meter for the property or is there just a CT clamp anywhere on the tails before the consumer unit? The installation manual for the Solax kit suggests either is posible but it seems to suggest a connection to a second meter installed before the consumer unit rather than just the household smart meter. The installer suggested a direct connection to the smart meter (though it was ambiguous, I will clarify when they come back) which would be a much more convoluted route and likely leave a lot of ugly trunking in the garage. Just wondering if this is normal or not? Thanks

Octopus currently pay 15p/kWh, so more lucrative than offsetting gas (for now).

May be of use. The in-line shutters are audible when it's windy (they don't stop hot air being sucked out), even when fitted close to the roof outlet. I would say subjectively though that they are effective, so have left mine in for now.

I think it just determines drying speed past a certain point. For example, my dehumidifier has a laundry setting which goes full blast for six hours with a target humidity of 35%, idea being you shut it in a small room. I don't use this as I find just leaving it at the standard 55% with doors open dries plenty quickly enough, maybe 12 hours? The dehumidifier is right next to the clothes and spikes to 70something when they first go out. Clothes feel bone dry by the time it's back to 55%.