Omnibuswoman

Thanks Wil. Yes I asked our builder to negotiate the company down a bit, and he then mentioned that his 10% has been included in the quote, which is in our contract. My irritation is that it seems that the original company is charging their full rate plus our builder’s 10%, even though they have an existing relationship with each other, and he is not getting the usual trade discount that would absorb his cut. I’ve also asked him to seek other quotes so we will see if they come back any differently.

Yes the scaffolding is still up as they are doing the roof now. Hopefully I can get this sorted swiftly so that the top layer of scaffolding can come down before long.

@SteamyTea in that case the cost looks quite reasonable. 8kWp for £10,500. Still, I will get some quotes for comparison.

As the roof is under construction, the panels will replace slates, so I’m not too worried about area as there is a cost offset there. My main concern is that the project is priced in the right sort of ballpark, as I know that PV costs have fallen a lot lately and finding information on the web is more challenging than I expected.

My experience with Western Power was that they initially quoted me almost £15k for something that, when challenged, may not have been justified. I spent a lot of time gathering information about local loads on the line as I was convinced they were wanting me to fund a local infrastructure upgrade that was already badly needed. After asking them for detailed figures on this, as permitted under the relevant regulations, they dropped the cost to £950. It’s worth taking a close look at what they are quoting for and it’s necessity for your project.

The interesting question has to be, if vector sum metering means that any electricity exported is offset against any electricity imported, how is a battery economically viable? Are we not just as well allowing anything that we don't use ourselves to go to the grid as an offset against what we have used? Or am I fundamentally misunderstanding how this works, and wronly assuming that any electricity exported in any given 24 hour period is offset against anything imported?? @Dan F @Nickfromwales

Just watched the video - a perfect idiot's guide to how this works. So in effect, it matters not how we set up the house demand across the three phases as long as we have a vector sum meter totting up total in and total out.

Thanks for your replies all. Bit of context: This is a new build, so the panels are going up (integrated into the roof) fairly soon. The array is 8kw spread across an E/W roof - roughly 1/3 on the E and 2/3 on the W. @SimC I had a look at PVGIS, but I couldn't figure out how to change the roof direction from South facing to East or West. Is that the figure in the box labelled Azmuth? I don't know how to express the direction in degrees, so any wisdom you can share on this would be great, thanks! Thanks for the comments about the phases and net metering. The 3 phase supply was installed last year by Western Power - their preferred choice for all new properties apparently. We have a digital meter on the outside of our workshop, adjacent to the house. I have gone back to the supplier of the quote to ask more questions about the inverter and phases - i.e. what his thinking is around this, and have cast the net to some other local suppliers for quotes to see what they propose. We don't yet have a smart meter - in order to get the supply connected we just went with the first company that could give us a reasonably short date for this - British Gas - many others were unable at that time to even commit to a date at all in late 2021. We plan to move our supplier to Octopus or Ovo, although we're a bit concerned that it might take quite some time to get a smart meter installed, judging by others' experiences here. For reasons of budget, we are not going to go with the batteries at this point, but will design the system to take batteries so that we can install them further along the line. The electrician we have chosen to do the electrics in the new house has no experience with solar panels, so we think we will have to find someone with this expertise to help to design the system, then to have our electrician fit it. I'll have a look at the posts that DanF referred to, and will do some more googling. I previously joined a forum for electrical and electronic engineers (in order to be able to negotiate with Western Power over the cost of the connection), so I may pose the question about phases and metering on there to see what pops up. Any knowledge I gain, I will bring back over here. Cheers, Omnibuswoman

I have reached the point of having obtained a quote for our PV system, attached, from a local company via my builder. Happy to hear any feedback on it - I thought it seemed competitive for an 8KW system with REC 365w twinpeak black panels. We won't be going with the batteries at this point for reasons of limited budget, but plan to add those in at a later stage. The total cost without batteries is £10,500. Before I seek further quotes, I really need to better understand how solar systems work for houses, and in particular with a 3-phase supply. I'm not certain that the quote provided is suitable for a 3-phase supply. My knowledge of electrical and electronics is really poor, and I need to have a look at an idiot's guide. Can anybody point me to the most basic of basic explanations of what each bit does, and where it goes in the system? Thanks!

Yes spot on. I tried modelling the shading effect but gave up as it was too tricky. Instead decided we should site the panels on the northern end of the East facing roof, away from the dormer.

Thanks @S2D2 Those are good points. I need to do some more learning about how PV and household demands work in real world scenarios - so far this is very much an academic exercise based on a set of figures for average household use. We may well be below that, although we do plan in the future to get a fully electric car and will use PV to charge that at home. I’m not sure what PVGIS is so I will look that up. Are you able to point me to an idiots guide to domestic solar PV?

@SteamyTea We've decided not to go for a heat pump just now on the grounds of cost v benefit. Whilst it would save us some money, the low level of heating needed, the use of PV for hot water for 2/3 of the year, and the use of WWHR means that it wouldn’t be likely to pay us back the outlay in its lifetime at current prices. We will leave the infrastructure in place so that when/if they drop in cost, and/or electricity prices rise further, we will revisit the idea.

no, I’m not wholly sure. Currently our heating and hot water are from condensing gas boiler. Our electric use is plug-in stuff only plus oven, so the new house being all electric will increase our use as our hot water will be from an immersion heater and our heating will be from low temp rads from same tank.

No, I’ve not heard of this. I don’t really understand the three phase thing at all. We had it installed as 3 phase as that is what the DNO specified, but have no idea how this benefits us or what impact it will have for our electrics. Our first fix stuff will be done in the spring/ summer, so I will have to gen up before then!

Thanks @ProDave. Yes, I will apply to Western Power and see what they say. Hope it's not as big a palaver as getting the supply in the first place. We have a three-phase supply here, but the local infrastructure is absolutely creaking and I can imagine they might be anxious about it taking any output from us. And yes, we do plan on getting a battery, I've just not looked into the cost of those as yet. That is the subject of another weekend's research!

I'm trying to compare the relative cost/benefit/pay-back period of different sizes of PV array in order to work out what size of array will be best, and wonder if anyone is interested in casting an eye over my maths to spot the errors...? The house will be passive house standard, around 200m2, occupied by a household of two adults with, we hope, regular visitors. The roof is a simple two-way (E/W) 32 degree pitched roof, around 75m2 per side, with a dormer window on the E side (photo attached). No shading from trees. The panels will be flush with the slates. We are in Cornwall. We plan to have a battery installed, but I haven't included in the calculations the cost of that. This is likely something we will add later on. Look forward to your thoughts... Solar Panel cost benefit analysis spreadsheet.xlsx

I should add that I am very happy with it so far. Occasionally I can’t get the feed to load as the mobile signal there comes and goes, but largely it is very easy to use and reliable.

We are using a Reolink camera to monitor our site. It’s battery /solar panel powered and uses mobile data via a special kind of SIM card (£4 a month). I can view it on my mobile phone and can play back recordings.

Wishing you both all the best - that sounds like a truly frightening experience. We are down at the mo, and will be down regularly now until our build finishes. Do give me a shout if there's anything you need. M

Ps It was £1.7million in the end, so equidistant between @pocsterand @Thorfun’s guesstimates 👏👏👏👏👏

It truly was breathtaking idiocy to give away more than 100% of the value of the work when it was only 20% finished. Very fortunate indeed to have his sister to supply his windows for free. Watching that made me feel an awful lot better about the minor rookie errors I have made!! 🤪

This windy??! It's storm Eugine mark II 😂

I was taught that must indicates a legal requirement that is enforceable, can indicates a guideline, and will is ambiguous, and usually deliberately so to lead people to think that something is a requirement when it is not...

Following this thread with interest as we will have an attic office room, and there is a risk of it being uncomfortably hot. We've flip flopped over the possibility of installing AC in the master bedroom (and potentially in the attic office directly above) as it doesn't fit with our position on environmental impact, but at the same time have concerns about being uncomfortably hot in our passive house. We have got quotes from Corner Star Aluminium for Warema external roller shutters for our East facing windows. I can't yet recommend the company as we haven't bought/taken delivery of the blinds as yet, but this is the option we decided to go for rather than external venetian blinds or louvres. For our South facing bifold doors we will have an awning above, which will also be the shade for the balcony outside. I'm not yet sure how practical an awning will be for days that are both sunny and breezy... We engaged a building physics company to do a PHPP overheating calculation for us, to see where we most needed to add external shading. We were able to reduce overheating by 85% (theoretically at least) by adding external blinds on the large East windows, and the awning over the bifolds. We are also planning UV reduction film on the two largest West facing windows. We are now mulling whether to add a velux external awning or external roller shutter to the only Velux window in the attic (West facing). I think that decision will be made only once the house is built and we have had a chance to see how comfortable or not the house/attic feels. @SteamyTea that weather website (WU) is my new go-to for nerdy timewasting, thanks!! 😂

New flats to be demolished and rebuilt due to safety fears https://www.bbc.co.uk/news/uk-england-london-61399641