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Also, just thinking about the situation you'd be in if the voltage was 207V. It would mean that the local substation is under very heavy load from a local consumer and near tripping off. Therefore, the extra current produced by your inverter at that voltage might be the thing that prevents the grid from tripping. An argument may be that the current limit protects the cables, but I would guess that it's the substation transformer that is the limiting factor in almost all locations. In fact the areas where you may see voltage dipping to near 207 are likely all rural with pole transformers and long lines. Likely meaning that a generator closer to the consumer may reduce the voltage drop in the lines and be even more beneficial.

Would expect you to use the nominal voltage for these calculations. ie, 240V. Up to the network to be designed for the variance.

100% though knowing this country the 'smart' solution requiring 24/7 internet connectivity is what will get proposed at some point.

This is exactly what's being proposed by the grid (see the link I posted earlier). Reducing the minimum acceptable voltage to 207V. Modern equipment shouldn't really care about the voltage being that low (the minimum voltage in Europe is 207V and almost all electronics we have bought in the last 30 years have been designed to work in that market). Link suggests a 4% reduction in resistance heating output, slightly dimmer lights. Most tricky issues being non-inverter driven motors and UPSes with to high a brown-out setting (likely can be adjusted).

... Huh? This is what I was proposing which I think you just called unnecessarily complex? Am I misunderstanding something?

It's not a gift. It's part of the value of the home. Sure there are buyers out there that don't value it, but plenty do and the number that do value it will only go up as EVs become dominant. If you hold on to your property for 5 years, the odds are the buyer in 5 years will have an EV/PHEV or be actively planning to get one so they will see the value. In the meantime before you sell, having a charger already installed means that it's available for guests and also lowers the bar next time you replace your car and unless you are a committed petrolhead then EVs are likely to be the best choice when you do so. (As I said earlier the rate of improvement and cost reduction in EVs means that the reasons not to get an EV are vanishing fast). I get the argument that compared to other costly building regs requirements that we may not personally care about (of which there are many) that EV chargers are very easy to retrofit once the wiring is in place and therefore shouldn't be mandated. But rules are inevitably compromises and it's better to have a simple rule that says 'new builds must have car chargers' than to say 'all new builds that will be sold within 5 years, rented out or can reasonably be expected to need to accomodate an EV within 5 years must have chargers'. There are alternative ways to get to the same result but I'd guess they are all much more intrusive and costly.

Changing grid frequency is how the overall grid responds to load as frequency directly affects power generated due to the spinning generators that make up most of the grid. Software driven inverters have more flexibility. They are not constrained by big rotating turbines and generators. So I believe it is possible to inverters to choose how many amps to export independently of the frequency and therefore have a configuration option to have a voltage level where output is tapered off that is set below the max voltage trip. Given our grid runs quite close to the upper limit in many places the scope for this currently may be limited, but there are plans to change the acceptable voltage range of the grid (https://www.efixx.co.uk/Articles/Proposed-Changes-to-UK-Mains-Voltage-Limits-Explained) and if that happens the the average grid voltage might drop. This would give more room to inverters to generate in the first place, but might also give room for regulations to support sensible production reduction above say 250V to produce a more stable grid when lots of inverters are online at peak times. Wouldn't hold my breath for it though (would seem like the sort of thing that would already have been proposed to align with the voltage change if it was going to happen).

Is there anything you haven't done?

Not sure that's right with switching inverters unless programmed to do so. Got anything to back it up? Their internal voltages will be higher than the grid limit, their limitation will come from the voltage seen on the grid line. So they should be able to output the full current up to cut off.

I'm not, but Ohme chargers are £415 + vat and if you are building a new house you don't pay VAT and your electrician bill overall is significant. The standard installation charge includes the wiring that this thread as talked about as the middle ground. My statement is that if you are adding the wiring anyway, then adding the charger shouldn't cost much more than the cost of the charger. The electrician is there anyway running the cables. It may be that you've got caught out here and didn't initially plan on installing the charger and now getting people back to do so is expensive. Obviously that's unfortunate and not a great situation, but it's not the general case.

It's not quite that though. Depending on the situation is equivalent to 'I'll pay for a taxi/train ticket to get you to my place'. If it's a child coming to visit then maybe it makes sense. If it's a contractor coming to do work for you, it doesn't. It's nice to be able to offer the generousity if you have the means but even semi regular charging by guests could be a substantial drain on some people*. Especially as the bills tend to come much later so the scope for running up bills and not seeing the impact until months later (when the electricity company revises your direct debit). * This is a self build forum that has a very specific audience who are much more likely to be knowledgable about these things, have solar, are relatively wealthy so the impact of charging might be less. But in a world where the EV charger is a legal requirement for any new property, plenty of people who know much less, are less wealthy, etc, will be living in places with EV chargers soon. So with that in mind, my view is that if you drive an EV and you ask if you can charge your EV at someones house you should always offer to pay (generously) for the priviledge of charging and only accept free charging if very confident the person offering understands what they are offering.

I'm at that point when I'm spending time thinking about parents increasing needs and having homes prepared for future accessibility needs seems completely sensible. In many ways it would be good if all homes had to be built with this in mind as retrofitting a building not designed for it can be much more troublesome/expensive at what may be a very stressful time. The regs only require it if the PP says so because requiring it everywhere would prevent some homes being built (mostly tiny starter type homes). I'm generally in favour of less mandates, etc, in regs but this one (and functional EV chargers) passes the bar for me. (I see the argument for just putting the cables in for EV chargers, but the extra cost of installing the charger if all the prep work is done is very small and if it's there it will get used*). * We are at about the point now where EVs are same price or cheaper to buy than combustion (before accounting for fuel costs) and it's only going to swing more towards EVs. China is already making 1500km range, 6 min charge EVs, so the reasons for not getting an EV are diminising rapidly.

That's a pretty stunning change.

This poor self certification does seem to be at the root of many many problems with UK construction. We seem to do it an awful lot more than other countries. In an attempt by governments to reduce bureaucracy and the cost of running building control they've created a huge mess where contractors can get away with terrible work and this drags the whole industry down as the good contractors find it difficult to compete. I watch a selection of people building houses, etc, on youtube and they all seem to have to deal with a lot more inspections/controls than we do. Either building inspectors or possibly supervising engineers who have to put their licence on the line to sign off the work. (ie, they sign off the design and then inspect). I'm not sure how we could move back to that sort of system in this country, seems like a mountain of work to undo decades of bad practice/habits and loss of experience.

Inverters have overvoltage protections built in. They shut down when the voltage gets too high and there are at least some saying that the limits imposed on inverters are too strict so they are likely to turn off too early. Doesn't mean there might not be problems with significantly excess provision on a local network but the protections for safety are already there. The inverter size limits are I think it's a way to prevent existing installs having to shutdown due to new installs. Given the benefit of solar outside of peak production I feel if these are the reasons they should be reassessed. It's feasible for a standard to be made so that inverters scale back their output gracefully rather than trip off. If that could be done then I'd guess the whole approval process could be significantly simplified (and people would be more likely to install bigger systems that might be limited in peak but net produce a lot more outside the peak).

If you are struggling for a plumber locally, maybe it's time to ask here for recommendations for good plumbers who are willing to travel (if you are willing to pay). Get someone good in who can resolve everything in one go. Will likely cost a lot more than you are paying for crap plumbers but if you can avoid the callbacks/issues then still probably a win. Alternatively, DIY?

Sure. I made a general statement, doesn't mean there aren't exceptions. Most people don't have 7p rates at night, bigger batteries in cars is increasingly common now the price of the batteries has plummeted, charging during the day on some tarriffs can be more than 30p/kwh. I admit that £30 is probably high but £20 is very much realistic for a charge from 20% for someone with a 80kwh vehicle.

Not a hard rule to me but should be the default unless either the host has massive solar and the energy is close to free or is sufficiently well off that the cost is inconsequential. I don't really have a problem with a short charge costing almost nothing, that's no different a offering a guest a drink, but if you show up somewhere with a low battery I don't think you should accept a full recharge without paying. With EV chargers being mandated they will be increasingly installed in places where the owner doesn't use them and therfore may not be aware of what a significant charge costs or necessarily be on the right tariff to use them cheaply.

No of course. Definitely support them being there as having a destination charger makes some journeys with an EV much easier. So it should be there for guests or future owners even if the current home owner themselves doesn't currently have an EV.

Ok, sorry, my mental maths was off. Still, different people are on different rates. Some people may pay a lot more during the day for electricity, some people have pretty low incomes (pensioners). So as a general rule I don't think EV owners should expect or accept free charging from their hosts.

Depends on the charger. Basic 16A one sure, £1.80 may bit on the high side for that, but plenty of chargers getting installed are the 7kw type. Someone local popping round for a coffee isn't going to need to charge their car. The people who will need to charge are those who have just travelled 150 miles to visit for at least many hours, quite possibly overnight. Big charges like that do add up.

I think that's a little unfair. Charging an EV could cost £30+ in electricity. That adds up fast if you have regular visitors.

Understandable but EVs will lead to a mindset shift here over time. Charging at home is much more convenient and half the price of charging mid journey. I would expect an EV driver to pay for the electricity they use but assuming you enjoy the company of the person visiting, them paying you for the electricity is a good deal for everyone. They get to spend more time with you, spend less on recharging and spend less time waiting to charge.

@Pocster How desperate are you?

Has been a possibility != every heatpump uses this as the solution. Reversing valves were at one point one of the more expensive components in the system so I'm guessing that in the past some manufacturers cheaped out and used alternative means for defrost.