SBMS

Hi @Marvin This is interesting. I think the inverter referenced outputs AC at up to around 20A so you’re right that would be a limiting factor. I guess multiple inverters could fix this? When you say max power you can draw from batteries is 40% - not sure what you mean here? I’m just trying to understand where the 80kwh storage to serve 28kwh of required energy comes from? Are you saying the AC to DC to AC conversion process is only 35% efficient?

Thanks!

Hi I am looking into battery storage options for a new build and as I understand it need an AC inverter or charger and then some batteries. At the moment it is looking like PV is a no go because of roof design so I am purely looking at charging from the grid. I plan on charging a 28kwh battery array on Octopus Go for the 4 hour period and then effectively running all the house off that stored energy, procured at 7.5p. On single phase I’m assuming that the maximum draw can be 32A to produce 7.4KW. My question is when looking at inverters/ chargers they have a KW rating and I wanted to understand - is this the maximum KW that the inverter will pull from the grid? I was looking at, for example, the GivEnergy hybrid which has a 3.6 and 5 KW version (https://www.givenergy.co.uk/pdf/Version 2.0/Hybrid Inverter.pdf). Would this mean that the 5 KW would, over a 4 hour period, only be able to charge 20kWh of my battery array? Or have I got it completely wrong? thanks!

It does. Roughly speaking its 300k for everything up to second fix, then 125k for second fix, which is broken out: ASHP (after 5k grant) £6,200.00 MVHR £7,000.00 Second Fix Joinery £16,500.00 Porch £3,000.00 Kitchen £35,000.00 Second Fix Electrics & plumbing £11,000.00 Landscaping and gardens £20,000.00 Flooring £9,000.00 Tiling £5,000.00 Decoration £5,000.00 Sanitaryware £7,000.00 The main ambitious bit is probably second fix electrics which is probably on the low side. Kitchen is designer high spec, completely outsourced to a subcontractor kitchen specialist. Bathroom second fix is through plumber, and we will be purchasing sanitaryware (so no Bathroom designer or subcontractor for that). Bathrooms are mid range (Grohe or Hans Grohe for taps, Roccia sanitaryware). Flooring is subcontracted out (LVT downstairs @ £60 sqm, Carpets elsewhere at £33.50 sqm).

@IndySo below are the prices per sqm and sqf as per our quote and what we are working to. I've worked out the total size of the house floors (walls included) which is the gross external, then the gross internal (everything except the external walls, so these includes studwork and eaves voids on 2nd floor) then our final actual usable internal floor space (which excludes studwork and eaves storage on 2nd floor): Sqm Gross External Gross Internal Usable internal Area Total size (sqm) 319 279 262 Total size (sqf) 3433.716 3003.156 2820.168 Total build cost (per sqm) £1,337.93 £1,529.75 £1,629.01 Total build cost (per sqf) £124.30 £142.12 £151.34

And do you include cost of electricity/BT connection?

And is the garage included?

Yes - although quick question for the forum. When calculating cost / sq meter, do people tend to do it off usable internal sq meterage? Or total square meterage?

We're just about to start construction on our self build. It's main builder led so am not doing anything ourselves. If anyone is after any prices for things (roofs, joinery, ASHP, windows, doors, aluminium sliders, garage etc) let me know as I found pricing up one of the hardest things when starting out. I ended up being miles out! Build is in Lancashire, traditional brick and block, blown insulation, traditional roof.

Not sure about the DPC but I believe there was evidence in the 70s and 80s of the plasticiser in the PVC cable migrating into the beads if in contact, and degrading the EPS. I don’t think that’s an issue anymore, I think there’s a chemical additive in the beads to mitigate this (anyone confirm this?). If you were really worried, then just put any cables in some 15mm pipe through your cavity - we are probably just talking about wall lights and maybe outdoor sockets? Anything else going outside should probably be armoured.

Lancashire

I did say all the TF drawbacks could be mitigated! Every construction method has its drawbacks. You’ve just listed ways to combat some of the drawbacks with timber frame. The same can be done for brick and block - or ICF - or SIPS or whatever really. They all have pros and cons. Downsides to brick and block can be mitigated in exactly the same way - but doesn’t mean I think everyone should build brick and block (and that those that don’t aren’t in the 20th/21st century ?)

Ah, bad luck. My brother (small scale developer) swears by the Ecodan units as a great balance between price and performance.

Consider an MCS certified. You can then get a £5k grant from the government Boiler Upgrade Scheme. We are having a Nibe f-2040 12kw, 300l cylinder, buffer, controls and all pipe work - 11k installed. Will cost us 6k. And the nibe isn’t cheap.

Risk of rot Poorer sound insulation Timber fraction to insulation ratios need considering Some Mortgage lenders don’t like (at least want an outer brick leaf) Issues with shower movement Each or these can be argued against I know, Im merely pointing out that you cant evangelise a construction method to the exclusion of all others. Went through a lot of research when looking at construction methods for our new build but came back round to traditional. That’s not to say that there’s some great advantages to timber frame. But timber frame is hardly new or innovative, like all things there are a hundred factors to consider (one of them being whether you’re in a wet climate!) when considering any individual build.

Are you diy installing the ASHP or using an MCS accredited installer?

So we’ve just been down this route. Initially we were going 100mm pir but after looking into it decided to go blown EPS beads. I increased cavity to 150mm (should be fine if you’ve standard width foundations). Ours is also exterior facing brick. Cost difference: 272 m2 of cavity insulation required : about £4900 plus the labour for the brickies to fit. Pumped insulation by outside specialist contractor - £4200 - with a 25 year guarantee. Means the build will go up quicker (brickies just focus on laying block and brick) and have a much greater chance of a fully, well insulated cavity. FYI the beads are water resistant and don’t transfer water across the cavity. Water that does get into the cavity naturally flows down the beads between the balls rather than across the cavity.

You can apply the same logic to every single item you might put into a self build. PV? Battery wall? Solar water heating? Rainwater harvesting in case water rates go up? MVHR? 150mm insulation? 250mm? 500mm? It’s pretty much an endless list of options. With an unlimited budget - sure, I’d go for every single one. Unfortunately I don’t; so every single decision that we make weighs up the cost versus risk versus return on that capital investment. In isolation it’s probably easy to say ‘it’s only 1k’. But they add up and this was why I was asking those more experienced in electrical current loading whether this particular investment would make sense.

Out of interest @Carrerahill what sort of a load would justify 3 phase?

Thanks this is really useful and I’ve definitely learned something tonight. The person at the DNO did say they’d only had 3 properties in a year that could justify the upgrade to 3P so maybe it’s be ok?

FYI the DNO offer a scheme where if you can demonstrate an insufficient single phase supply owing to the installation of green appliances (ASHP, car chargers etc) then they will upgrade the supply to three phase free of charge. This is only relevant for an existing single phase supply. Would my scenario demonstrate this?

Sorry are you saying that in my scenario with those 4 appliances operating they wouldn’t draw 100A off the supply? Or are you saying the DNOs capacity calculations wouldn’t see this as a valid scenario?

I’ve been told single phase is 100A and 3 phase is 80A per phase for a total of 240A

Yes this has been my consideration. If i turned on: Oven: 13A Hob: 32A ASHP: 23A Car Charger: 32A then boom... I've maxed out my 100A single phase connection.

Thanks @PeterW. In North west - Electricity North West. £1500 for single phase connection, £2500 for three phase ?