Jeremy Harris

They all vary a bit, and one problem with built in cisterns is that there often isn't much room inside to fit the fill valve without the float touching something and perhaps jamming. You can repair the valve you have, as the chances are the diaphragm has a small hole or split in it, but a new diaphragm is around £3 and you really need to take the fill valve out to gain access to it, anyway. By the time you've done that it's easier to just fit a new valve. One of the plumbing experts here will know whether there's a more reliable side entry fill valve that will fit in the same space as that Siamp one, perhaps. If not I'd just replace it with the same one - they usually seem to last for around 5 years before failing, from what I can gather.

Pretty sure it's this one (swap the bracket over from your existing one) : https://www.toiletspareparts.com/collections/siamp-toilet-spares/products/siamp-95l-side-entry-inlet-float-valve-1-2-15mm-plastic-30950607 Hopefully one of the experts will confirm or otherwise if this is the part before you splash some cash (although it's only £12).

I'm far from alone - @SteamyTea does just as many experiments to prove or disprove things. If I can't find any hard evidence to prove something I find questionable, the chances are I'll do a quick experiment to better understand it. I still have to dig out the two bits of PIR foam that have been sat outside with lumps of mortar on for months and see if the mortar has had any effect at all on the foil coating. Might dig them out next week and see how they look.

I'd go with that. I had a plastic bag full of blown bonded beads that I filled when the guys were putting in our CWI. I split the bag into two more or less equal lumps, let the glue dry for a few days, weighed each lump, then immersed one of the lumps in a bucket of water, weighed down by a brick, for a few days. When I took it out and checked the weight it was near enough exactly the same as when it went in. On the basis of one, impromptu and uncontrolled, experiment, I'd conclude that blown bonded beads don't absorb water at all to any significant degree.

I'm struggling to get my head around the concept of low loss, when applied to a 12 VDC supply for household LED lighting. LEDs are, as mentioned before, current driven devices, so all LEDs that have a voltage rating have an integral driver circuit of some description to run the LEDs at a current that's within their acceptable operating range. 12V LEDs, for example, have to have some form of driver in order to convert 12V DC to the constant current needed to run the LEDs themselves. Cheaper 12V DC LEDs may just use a dropper resistor, which is not as inefficient as it seems, as three white LED chips connected in series (inside the lamp itself there will be many LED chips) will operate at a forward voltage drop of between 3V and about 3.5V. depending on temperature mainly - as they warm up their forward voltage drop decreases. This means that arrays made up of three LED chips in series will run at a variable voltage of between 9V and 10.5 V, but ideally at as close to a constant current as possible. More expensive 12 VDC LED lamps will usually use a switched mode DC to DC constant current driver circuit. Both systems drop the 12 VDC coming in to a variable output voltage, but a near-constant current, that matches the rating of the LEDs. For example, I have some 12 V MR16 downlighter LEDs that have 24 off 5730 LED chips, wired as an 8 x 3 array (so 8 parallel connected rows of 3 LEDs in series). Each 5730 LED has a constant current requirement of around 150 mA. To get approximately 150 mA through each of the 8 row of series connected LEDs, each row of three LEDs has an 18 ohm resistor in series with it. This isn't ideal, as it means that the LED current will vary a bit with temperature, but it's safe enough, as the maximum allowable current for a typical 5730 LED chip is around 200 mA. Analysing the efficiency of this arrangement for a constant 12 VDC supply we get: For LEDs operating at their lowest forward voltage (Vf) of 3.0 V, then the row of 3 in series gives a voltage of 9 V, and the 18 ohm resistor therefore has a voltage across it of 12 V - 9 V = 3 V. The current flowing through the 18 ohm resistor (and hence the row of three LEDs) will be 3 V / 18 = 167 mA, within the 200 mA maximum allowed. The power loss in each of the eight 18 ohm series resistors will be 0.167 A² * 18 = 0.502 W. The power in each LED will be 3 V x 0.167 A = 0.501 W. A row of three LEDs will give a power of 3 * 0.501 = 1.503 W. The efficiency at this operating point for a typical resistive dropper LED driver will be around 75%, a pretty low figure, but this type of 12 V LED is common and cheap to make. For LEDs operating at their highest Vf of 3.5 V, then the row of 3 in series gives a voltage of 10.5 V, and the 18 ohm resistor therefore has a voltage across it of 12 V - 10.5 V = 1.5 V. The current flowing through the 18 ohm resistor (and hence the row of three LEDs) will be 1.5 V / 18 A = 0.083 mA, well below the best operating current of 150 mA, so less light will be produced. The power loss in each of the eight 18 ohm series resistors will be 0.083 A² * 18 = 0.124 W. The power in each LED will be 3.5 V x 0.083 A = 0.29 W. A row of three LEDs will give a power of 3 * 0.29 = 0.8715 W, a fair bit less than for the 3V LED Vf case. The efficiency at this operating point for a typical resistive dropper LED driver will be around 87.5%, about the same as a switched mode driver circuit, but the power of the LEDs is much lower than their are rated for. If we now look at either an AC-DC constant current driver, or a DC-DC constant current driver (doesn't make a significant difference, both will be around 85% to 90% efficient) then the primary difference is that no matter what the LED chip Vf is, the drive current will be a near-constant 150 mA. This means that maximum light is obtained from the LEDs, and overall the efficiency is almost certainly going to be at least as good as, probably better than, the simple resistive dropper. So, until someone comes up with a true, high efficiency, 12 VDC light source, that doesn't require any form of energy-sapping driver, it's pretty hard to beat either an AC-DC constant current LED or a DC-DC constant current LED. If you know of any 12 V intrinsically high efficiency light sources that don't need the drivers that all LEDs need, then perhaps you can let us know about them, as that would then swing the argument in favour of using a 12 VDC supply with 12 VDC switching. Possibly. The building regs approved docs and BS761 are a bit silent on ELV DC switching standards, AFAIK, but if a building inspector was satisfied that a switch used in a house was suitable for the purpose, then there's no reason not to allow it, AFAIK. It should be easy enough to provide evidence that a switch was suitably rated for DC use at the current it was being used at, and I reckon most building inspectors would be OK with it. In general they don't seem that bothered by ELV stuff, anyway, AFAICS.

Best bet is to sort out and photograph your late husbands tools, post them here in another thread, and we will look at them, name them for you and you can then label them so you know what they are. I suspect you already have all the tools you could possibly need, and all you really need is a way of identifying them. If you want to be really professional, then see if you can stick up a board in the garage to put all the tools on, with names written by the peg or hook for each. I have a bit of cheap MDF on my old garage wall, with loads of nails driven in to hold tools. I pencilled around every tool when it was on the board, then took all the tools off and painted inside the outlines of every tool with some left over paint and a small brush. Took about an hour to do, but now I can glance at that big board and see if any tool is missing. I didn't bother with labels, but you might find it easier to label the "shadow" of every tool on the board, so you can find it easily. It's a tremendous help just being able to look at a board to find any tool. There's also a great deal of satisfaction in fixing things yourself, especially the first time you do it. I find it's not really about the money saved, it's about the personal achievement,

With respect, Paul Buckingham's view are not those of the AECB, they are just his personal views, much like my views, or your views, expressed on this forum are not the views of Builhub.org.uk Personally I can just ignore any political element of a rant like this and focus on the technical points being made, and I think both his papers have merit for highlighting what is an endemic problem within the UK house building industry. I have no idea why big developers build to such low standards. Poor regulation is clearly an issue, as is a lack of pride in their workmanship by those they employ. I strongly suspect that time pressure to get houses to market quickly is a factor, and that there is a cost saving element that drives such crappy standards. Whether that is directly of indirectly linked to profit I'm not so sure about. I can't help thinking that having to repeatedly come back to completed houses to undertake major snagging and warranty work must hit the bottom line harder than just building the damned things properly in the first place. There's a quality policy I remember from a week I spent up at Nissan in Sunderland, seeing how their quality systems worked. They costed every second of a line stop due to a quality issue and charged the supplier of the defective part that caused the line stop. I can't remember what the line stop costs were, but they were well into the hundreds of pounds a second. Whilst there I saw a defective window operating mechanism that stopped a line and the manufacturers of all the components of that mechanism literally ran to the car on the line that had created the stop, and rushed to determine the cause and rectify it. I remember talking to the window motor manufacturers rep as he walked back, relieved that it wasn't a part his company had supplied that was out of spec. If house builders adopted a similar "quality first" approach, where they aimed to have zero snags on every new house built, things could be a lot better. Right now I've been told that if they get a snag list that's "only" got 50 problems on it they reckon they are doing OK, and only really start to see if they can improve when snagging lists get up to around 200 items per house.

Be interested to hear your findings. I should add that my measurements of PF, power etc were done using a relatively cheap HOPI meter: Hopi meter and I would give a strong health warning to anyone thinking of getting one of these that, although they are pretty accurate and reliable, there is NO WAY they meet any normal UK/EU safety standards, so use with extreme care! Fine in the hands of someone that understands all the potential risks they present, but it still needs treating with caution.

Why emphasis "people on this forum" in such a derogatory way? The hard facts are that unless you have a low loss DC supply that is at the correct voltage to run LED DC lighting, then you are still going to have the same order of conversion losses in converting that DC to the constant current drive required for LED lighting. LEDs aren't voltage driven devices, they are current driven, so some form of constant current driver is required and it doesn't really make a jot of difference in efficiency terms as to whether that constant current driver is supplied with AC or DC. Boats are a subject to a different regulatory regime, and boat switches are specifically designed to switch high current low voltage, DC loads, and usually be weatherproof and sealed so that they cannot initiate a gas explosion (at least the better ones are). The hard fact is that I could not find a single manufacturer of approved house wall switches that either manufactured a switch designed to switch DC loads, or that would provide a de-rating factor for any of their switches if used to switch DC. The major problem is that all domestic light switches, approved to EN 60669-1, have very slow moving internal contacts. When you switch off a normal 10A rated wall light switch the contacts are really slow to open - this doesn't matter much for AC, where the voltage across the switch drops to zero every 10ms anyway, and it makes the switch cheaper to manufacture. If you look inside a boat or car DC rated switch you will find it has a more complex contact mechanism and includes and accelerator spring to make the switch contacts open very much faster than those of a domestic light switch. This toggle action is there deliberately to ensure the opening arc is very quickly quenched, by moving the contacts apart vary quickly, and also by including a significantly greater gap between the opened contacts, so that no arc can be sustained during switch off. It would be possible to design wall light switches to operate like this, but may well increase the depth of the switch. For a host of reasons, domestic light switch manufacturers strive to keep the switch depth as slim as possible. Including a toggle-type switch contact mechanism, with an accelerator spring to separate the contacts as quickly as possible, would mean turning the contact orientation within the switch through 90 degrees and almost certainly result in deeper switches. If you really wanted to switch, say, 12v DC with wall switches, there's no reason I can see not to buy blank wall plates, fit deep wall boxes and fit approved DC toggle switches to the blank plates.

That sort of crap workmanship is, I'm afraid to say, pretty typical. Paul Buckingham wrote a paper a while ago that highlighted how widespread work like this is: Paul Buckingham paper and followed that up with another paper a while later: https://www.aecb.net/still-taking-disgraceful-approach-build-quality-waving-goodbye-energy-savings/

The same this seems to happen with every government incentive scheme. Years ago, when we had cavity wall insulation installed, there was a government grant. Just for a laugh I rang around a few of the larger installers and asked them to quote to install blown bonded EPS bead insulation into our house, stressing that we were not eligible for any government grant. The prices varied between £300 and £350. I then waited a while and got more quotes, this time stressing that we were eligible for the government grant. The prices were the same, £300 to £350. The bottom line is that the installers just looked at the grant as being additional profit, rather than something to reduce the price to homeowners. The same is true for just about every scheme going, and I'm damned certain that developers have factored in the Help to Buy assistance into their "starter home" pricing.

AFAIK, the regs haven't caught up with the potential fire risk or risk category that should, perhaps, apply to battery storage, especially that using lithium chemistry cells. The risk is probably pretty low, even though the perception of risk is higher than it perhaps should be. My view has always been that the battery storage will be outside, away from the house and in a steel shed or housing against a concrete wall. I measured the PF of our inverter driven ASHP, it seems to be around 0.7 PF when running on part load. it's probably a bit better when more heavily loaded, I'd guess. I've not measured our MVHR, but that uses switched mode control of the fans and the ASHP, so would expect it would be around the same. The LED lighting is all run on switched mode supplies and is around 0.5 to 0.6 PF. With respect, you didn't get "negative feedback" at all, just some uncomfortable facts about the non-availability of DC rated light switches, based on my asking every manufacturer I could find whether they could let me have the safe DC load for their light switches (none could). The fact is that no one yet seems to make wall mounted light switches that will accept low voltage, relatively high current, DC. If you want evidence of the difference between switching AC and DC with a standard light switch, and the arcing that occurs under DC loads significantly below the switch rated AC load, then John Ward (who I have mixed views about) has a video on his You tube channel that illustrates the issue well: John Ward DC light switch testing video One way around the DC switching problem (but doesn't address the losses issue - see below) might be to change the relays inside one of the remote switching systems available. I've just fitted the Quinetic light switch system and found it works well. The receivers have internal relays rated at 16 A AC, and in all probability you might be able to either obtain the safe rated DC current for these, or replace them with suitably rated relays. The only other problem to overcome would be to modify the internal circuitry to operate on whatever DC voltage you decided to use, as at the moment the receivers have an internal AC operated power supply (that may work on DC - I've not looked to see if it's a switched mode or something cruder like a capacitive dropper - if the latter it will only work on AC as it stands). Looking at the losses, then a typical switched mode power supply feeding LEDs will be at around 85% efficient, it could be around 90% efficient, and it's perfectly possible to get up to around 93% to 94% efficient if the manufacturers really wanted to (for example, using synchronous rectification easily gets over 90% efficient). Battery storage systems vary in terms of the DC voltage they operate at internally. The lowest seem to work at around 48 VDC, some may operate at higher DC voltages. That means any DC lighting system still has to use a DC-DC converter to provide constant current drive to the LEDs if run from a storage battery, and that is likely to be around the same efficiency as any AC-DC converter, so offers no gain in efficiency terms

Not dodgy investment arithmetic if you are just looking at the possible savings a battery storage system may provide over not having one, and especially not if you are specifically pointing out that the return on investment is less than zero if taking into account what that investment may have returned if invested in the best possible, most tax efficient, savings scheme. As I tried to highlight, the calculation is extremely complex and subject to a lot of unknown variables, that may have a significant impact on any possible return. There's also the matter of valuing less tangible returns - for example, we have frequent short power cuts, what value should be placed on having a system that provides power to critical loads during power failures? To chuck in another variable, smart meters will introduce two factors that may significantly impact on bills (assuming that they will eventually become mandatory, as I am certain will be the case. The first is the adoption of short period tariff changes to match the variation in wholesale price. Best estimates are that half hourly, or perhaps hourly, "smart" tariffs will vary from around £0.05/ kWh to around £0.30/ kWh, with the highest rates being during peak demand periods (probably early evenings). Being able to use battery power during high tariff periods significantly swings the return on investment sums for a battery system. Secondly, "smart" meters have the ability to introduce kVA charging, rather than kWh charging, and I very strongly suspect that the suppliers will take up this option. It used to be the case that domestic use was considered to be around unity power factor (PF), but that's far from true. Virtually every domestic device, from a washing machine through to TVs, LED lighting, device chargers and power supplies etc, has a PF that's way below unity - often around 0.5 to 0.6. This places a significant burden on the distribution network and there is pressure building to switch to kVA charging for domestic premises (it's why "smart" meters have the option built in to register kVA as well as kWH). kVA charging would almost double the tariff for a typical modern home, with the majority of the loads having a low PF. A smart inverter (in fact most inverters) can apply a degree of PF correction by virtue of the way they sync to the grid. I've not looked in detail as to how effective this is, but it's noticeable that the PF of our house markedly improves when the PV system is generating, which has to be down to the way the inverter works. Our poorest PF loads are the ASHP and the MVHR (with it's internal air-to-air heat pump). Both of these use switched mode controllers, and run with a PF of between 0.6 and 0.7 at best. They aren't as bad as the LED lights, though, they run at a PF of around 0.5, but thankfully their total kVA is relatively low. Finally, you are an untypical example of a domestic user, @SteamyTea. You are very aware of your energy use and have taken significant measures to both monitor it and reduce it. At a guess I'd suggest you probably use around half the energy of someone in similar home that was not as energy-conscious.

Definitely Polish. Na zdrowie!

Unless the cistern is actually over-filling and the overflow is down the pan, as is often the case. In that case it may well be something as simple as the fill/float valve not being adjusted properly, so screwing the circled bit clockwise "should" cause the valve to shut off at a lower level and stop the overflow. Alternatively, the valve could just have failed and be letting by, in which case the best bet is to replace it.

Sure, happy to. What I've done is run a spare conduit that leads from our meter cabinet to a location around the back of our house where I could either wall mount, or most likely mount in a fire proof narrow shed (I'm thinking of getting one of those 5ft x 3ft steel lean to sheds for the job). This conduit is separate from the power cables and is there to run a data/sense cable from the meter tails to the battery system, in order to allow it to know when we are importing or exporting. The Sofar system (and I suspect other similar systems) allow the sense cable to be up to 20m long, so the inverter and battery pack can be around 20m from the meter (or possibly the consumer unit - depends on whether the consumer unit handles all the power - ours doesn't, we have two feeds from the meter that are taken off before the house consumer unit). For the power side, then you need two cables if you want to be able to fit a auto changeover switch to allow the battery to supply back up power to some circuits in the event of a power cut. I've run two lengths of 4mm² SWA from our meter box location to the location of the battery system (if we fit it). These are not in conduit, but are buried directly and are separated from the conduit by around 300mm in the trench, just to minimise the risk of any interference in the data/sense cable. I also have another spare run of 4mm² SWA that goes to the water treatment shed, giving me the option of having that on a switched back up supply (not sure it's needed, given our pressurised water storage capacity). The way this lot would work is this. The inverter/charger in the battery system senses whether the whole site is importing or exporting via the sense lead from the meter cabinet. The grid connection will be from an additional weatherproof termination by the meter cabinet that will connect to a spare RCBO protected connection to the incoming grid supply, on our side of the meter (I already have a spare slot in the weatherproof CU that we used as our temporary site supply). That takes care of the basic operation of the battery system, in that it can run in normal mode with just a single connection plus the sense connection to the incoming supply. If you don't need the option of a battery back up for power cuts, then this is all you need, in fact the power feed to the battery unit can come direct from a spare connection in your consumer unit, via an isolator, just as a PV system would connect. The second power cable is needed if you want the option of running some critical circuits from the battery system in the event of a power cut. To do this, the supply to those critical circuits (pretty much the ones suggested by @Ferdinand earlier) would be via a separate consumer unit, supplied from the main consumer unit via the changeover switch (either automatic or manual). The backup power outlet from the battery system would connect to the other side of the changeover switch. With an automatic changeover switch, then as long as the grid is up the switch will direct power from the grid, via a protected feed, to the essential circuits consumer unit. If the grid goes down, the auto changeover sense that and immediately (probably within a few tens of ms) and switches the essential supplies to the inverter in the battery system. When grid power returns the auto changeover senses that and switches back to the grid supply. In our case I'd selected the location for a possible battery system at the design stage, and allowed room for it against the retaining wall at the rear of the house, where it's in the shade all the time (good for helping to keep things cool). Putting in a few extra cables and a conduit run was pretty easy, my only regret is that I didn't include a direct extra run up through the slab to the house consumer unit. That would have made adding the essential circuits supply neater, rather than the arrangement I've ended up with which is a cable run to the water treatment shed and then joined to ones that runs into the house. Hope this doesn't sound to muddled!

I agree, and I think that's one reason the Pylontech battery units have been dropping in price a lot. They are now £906 inc VAT and delivery for a 2.4 kWh module, and it's only a few months since the same modules were around £1500, IIRC. I can see these battery modules coming down to perhaps £600 a module before too long. As the only difference between the 4.8 kWh, 7.2 kWh and 9.6 kWh Sofar units is the number of battery modules, and as the battery modules are user-replaceable, it may well be an idea to start small, say with a 4.8 kWh system, then look to add capacity if you find you need it and if the price of the battery modules drops further. The general rule of thumb is that about ten years is the life of an inverter, driven mainly by the life of the commutation capacitors, so the chances are the whole system would need replacing at around the ten year point.

If it was included as a part of the approved plans, then yes, it should be, I think.

I would assume a viable life of no more than ten years, and if you can use, say, 50% of the battery power every day (that's perhaps a bit optimistic) and you can charge the battery pack to 100% for 70% of the year (might be a bit pessimistic) and as long as your maximum demand when running solely on battery power is less than the 3 kW limit of the Sofar system, than I reckon some very rough sums go like this: Initial cost of 9.6 kWh unit, inc VAT and delivery, assume self-install (practical, but subject to Part P, perhaps) = £3,858 Assume 50% capacity used for every day charged (50% capacity and 70% days) = 255 days x 4.8 kWh = 1224 kWh/year Assume 10 year life gives energy delivered through life of 10 x 1224 kWh = 12,240 kWh Assume mean unit price of grid electricity over this ten year period is £0.16/ kWh (probably pessimistic), then value of electricity delivered from battery system through life = 12,240 x 0.16 = £1,958 Overall, based on these (probably pessimistic) figures, it's not viable in terms of energy cost saving alone. However. if you were able to use, say 70% of the battery capacity per day, and charge the battery enough to use this much for 80% of the year, then things change a bit to give a saving of around £3,140 through life, based just on energy cost. Things change yet again if the assumed mean through life energy price shifts. If electricity prices rose to a mean of say £0.18/ kWh, then both these figures increase by 12.5%. Another option would be to look at your loads to see how much battery capacity you really need. The 4.8 kWh Sofar system only costs £2,412 inc VAT and delivery, so if that's enough capacity to meet your needs then two things change. The likelihood of being able to generate enough PV excess to maintain the battery in a high state of charge increases and the unit price of the stored electricity drops. There's lots of variables that are hard to pin down when working out any savings, especially the ability to reduce day time import by using the battery to knock the peaks off the demand when the PV is not quite generating enough to meet it. For things like running washing machines, dishwashers of lower rate car chargers, this may well be a significant saving, but is pretty damned hard to try and quantify. I'm tempted to take the risk of a system not paying back for a few reasons. The value of having back up power to me is quite high - we get a lot of short duration power cuts that are a nuisance. I believe that electricity prices may well increase to above the worst-case ten year mean I've used above of £0.18p per kWh. I also know, from experience, that PV generation can be highly variable in the very short term, going from several kW to next to nothing and back over the course of a few tens of minutes on some cloudy days. The value of the electricity used from the battery pack during peak load events during days like that may well be enough to remove all day time import from the grid.

Pretty much as @Ferdinand has said. I already have the home file server, router, switch and VDSL modem running from a battery-backed UPS, so we have internet and wifi up during power cuts.

It is, you have to fit a changeover switch, but that's pretty easy. In the specific case of the Sofar system with the Pylontech battery packs, it has two 230 VAC outputs, one is grid tied and complies with G83/2, so turns off when the grid tie is lost. The other remains up and can be connected to power-critical systems, so the system works like an uninterruptible power supply. In practice, what I'd do is take the feed to the circuits I want to remain on when the grid fails out of the main CU to an auxiliary CU that is connected to an automatic changeover switch. That way, when the grid goes down those circuits just switch over to being run from the battery pack inverter. This is the same way that generator back up systems are connected, and the automatic changeover switch would be a standard generator backup one.

No, it's not more solar, we have more than enough, the Sofar is an inverter and battery storage system with a capacity of 9.6 kWh. It's not that large and I made provision to install a storage system when we built the house, so there is a base for a slim cabinet with a conduit leading to it plus two runs of SWA running close by. I've just been waiting for the price of battery storage to drop, and it seems to be almost falling like a stone. It's only a few months since a 4 kWh battery system would have cost well over £4k, and now we have 9.6 kWh for less than half that. It's still marginal in terms of return on investment at today's electricity prices, but close to the break-even point. Add in the ability to have up to 3 kW available via a back-up connection during power cuts and the convenience value that adds, and it's starting to look tempting. Another thing in it's favour is that it would remove short periods of import during the day, when the house or car charging load exceeds the generated power from the PV. Hard to factor in what that's worth, but at a guess I'd say perhaps 10% or so. The biggest advantage is that a system like this practically removes the need to monitor generation and only switch loads, like the washing machine, on when the PV is generating more than enough power to run it. The battery system would even things out on days with sun and clouds, so loads like this could run without the need for sporadic import.

Just checked and the price of the Sofar 9.6 kWh system has dropped again to £3,858 inc VAT and delivery. This is a system that includes a 3 kW backup supply outlet in the event of power cuts, and one where the price seems to be dropping very regularly.

There are already signs of DIY system prices coming down, especially battery systems. I'm seriously considering a battery system, most probably a 9.6 kWh Sofar system for around £4,500 inc VAT and delivery.

The government seem to have given a boost to small scale battery storage, as they've announced that not only are they scrapping the FIT subsidy next year, but they are also not going to allow microgenerators to be paid anything for any electricity they export to the grid. So, if looking to fit PV, then several things become paramount. The first is to maximise self use, which may lead to the adoption of East/West arrays, or even flat arrays, more useful than South facing arrays. Secondly, not fitting a PV diverter system to heat hot water with excess generation would be daft; it becomes essential to try and use as much electricity you generate as possible, as there is no merit in giving the power companies a free subsidy with energy they don't have to pay for. Finally, with the price of battery systems dropping, this move may well swing the balance to make home storage more attractive. Losing e few pence for every unit exported to the grid effectively increases the return on any battery system. That could make all the difference in terms of cost effectiveness.