How hard would it be to link panels to night storage heaters?
My garAge foof is big enough 19ft x 12ft to take 4 or 6 panels.
Could i source an inverter to feed night storage heaters so during sunny days they warm up, then i can open up the vents for a few hours in the evening, and maybe still have some residuals for an hr first thing?
Night storages are basically poor if used as intended, ie heat from 0100 to 0500, then loose the heat througj the day so you have little energy at 2000hrs.
Heating through the day then using then an hr or 2 after should be way better use of pv.
Do i need a power dump for when the heaters are all hot, i image they are pn a stat so turn off when the bricks are heated sufficiently?
Not fussed about export as the rates are not good.
Been reading up on hot sand energy stores but dont have the space for one
technically its possible to do but the difficulty is that high solar generation doesn't overlap very well with high heating requirements.
Can anyone Souhtampton area recommend the company they have used. Starting to get quotes etc together (though fully expecting it'll be next year before anyone good can install).
As for doing my own research where is best to start reading up. Target is to power daytime usage (both WFH) and ideally dump the excess into our Zoe (though I don't think the existing charger supports this out of the box, might need to write some code to turn it on at a reduced rate when export is detected).
Placement on roof + some on garage roof seems about right based upon how the sun moves round but I have a 4 sided hip roof so panels won’t all be getting sun at the same time
Just seen this, you may need extra inverters. We also have a 4 hip house roof, and gables on the garage. We have 9 panels on the SE facing house roof, and 6 on the SE facing garage roof. We already had a mains cable to the garage, options were to lay a DC cable or have one inverter in the garage and another in the house (which we did). We were also told that inverters can only handle panels that are producing the same output, so SW facing panels would need a separate inverter to SE facing - but that was in 2011, inverters may have improved but worth checking. We were also told that panels in landscape orientation couldn't be on the same inverter as panels in portrait, but I have heard that's not necessarily a problem now.
We were also told that inverters can only handle panels that are producing the same output, so SW facing panels would need a separate inverter to SE facing – but that was in 2011, inverters may have improved but worth checking.
I'm fairly sure that's rubbish and typical of the stuff spouted by 'installers' around that time!
The installation at our main house went in arounf 2011/2 and is split E & W with one extra panel on the West facing roof - we had a Growatt inverter fitted that can handle multiple strings and all is good.
That said it's not the inverter that was fitted initially - the first one only had a single input. I pointed this out while it was being installed and they came back a couple of days later and swapped it for the correct one.
The alternative is to fit micro-inverters to each panel.
The alternative is to fit micro-inverters to each panel.
or tigo panel optimisers
Can anyone Souhtampton area recommend the company they have used. Starting to get quotes etc together (though fully expecting it’ll be next year before anyone good can install).
I've recently had panels installed via Empower based in Ringwood. I've had a mixed experience so far.
Scaffolding sub-contractors broke a number of tiles and put ladders into the middle of hedge. Actual install was great, but since then I've had a mixed response to a few questions I've posed via email, but had decent support when I've found the time to ring up
booked in for the 15th November. 4kw with 3.6 inverter and 2.4 battery. will update as it goes along
Disappointingly, our Solar Together quote fell through as we’re pretty non-standard…
Reason they gave is that the inverter they have on that offer needs 6 panels to support a battery installation.
We have room on the garage roof for 5 panels ( The house roof can only support 2 panels as we have a loft conversion) - question for the knowledgeable folk on this thread, is it worth me investigating this further or is it a non starter?
So we are just literally switching on now...
Have had 2kw of panels on a South facing shed roof for 8 years but we had to redo the roof on the south facing part of our house so have had flush/inset panels put on as much of it as possible which adds another 5.4kw of generation (these have optimisers on them). The roof is dead south facing and unshaded s should be ideal.
We have a 15kw battery on the system too now, literally just wired in (!), a solar iboost (had for 8 years, a great bit of kit) for hot water and a Zappi car charger.
I think we ought to hugely reduce bills. Fingers are crossed!
Other eco things we have - solar thermal hot water and a biomass boiler (no mains has where we are!)
Anyone seen this? I read the article earlier today, and it looks like it could go a long way to expanding the use of solar for personal urban use. I looked into having PV roof panels fitted, but due to the layout of my roof, because of the size of standard panels not enough could be fitted to make it viable.
https://www.thebrighterside.news/post/eco-friendly-solar-panels-generate-energy-without-sunlight
Here’s mine and the neighbouring houses; they’re all three-bed semis, facing due north/south. The back of the houses have one long roof, but it’s divided between two houses, so unless two households shared one set of panels there’s not enough, and even then sharing would amount to the same situation. In my case, the next door house is split into two flats/apartments, just to complicate matters.
Some sort of small tile/panel that could be used to cover the roof and walls would be ideal.
We have our order placed and waiting for our survey. 5.6kW PV with an 8.7kW battery and an iBoost for hot water. A big cost for us is gas to heat our water using our inefficient and old boiler. Looking forward to the iBoost Solar Diverter helping with that.
Now I need to consider the replacement of our old immersion tank to maximise that benefit. We have space of for a larger one so what size and type is recommended? There are 3 of us in the house now but daughter will probably move out in around 12 months or less.
Now I need to consider the replacement of our old immersion tank to maximise that benefit. We have space of for a larger one so what size and type is recommended? There are 3 of us in the house now but daughter will probably move out in around 12 months or less.
how will replacing the tank benefit you? if you're not running it to empty, then the extra water will just sit in it staying warm, and not need heating up the next day.
What makes you think we are not running it to empty? We are as it is too smal. We maybe get 2 short showers before having to heat it again using gas which is costly and slow. Im not sure of the size but I suspect less than 100 Ltr. A 200 Ltr tank would allow us to heat a larger volume of water which will allow 3 showers at peak times.
What makes you think we are not running it to empty? We are as it is too smal.
fair enough, its an unusual circumstance because most hot water systems are sized to the house - 100l is properly small.
In the mean time, try heating the tank to 65C (or hotter) - you'll get a lot more shower out of it that way.
Now I need to consider the replacement of our old immersion tank to maximise that benefit.
I'd go with a 225l (min) unvented tank.
About 6 or 7 years ago I bought a used 225L Megaflo for about £125 off eBay and had that fitted in our beach place to replace an old, smaller vented copper tank with jacket.
One of the best moves I've made in ages!
No CH and the 3Kwp array provides 99% of the hot water from April-Oct (it's currently 56.375c) with a minimum of 3 of us there at any one time.
In that time it's been faultless.
Ideally I'd have fitted at 250L tank as we have at our main house but I didn't quite have enough space.
In the mean time, try heating the tank to 65C (or hotter)
The thermostat on our Megflo immersion is set as high as possible and it maxes out at 62c which is properly hot.
I’d go with a 225l (min) unvented tank.
Looking to increase to that capacity, give or take, as we have sufficient space but we currently have a vented system and a shower pump to increase the pressure. Fitting an unvented cylinder may make the pump redundant but we have an old gas boiler so not sure if this would create an issue.
Fitting an unvented cylinder may make the pump redundant but we have an old gas boiler so not sure if this would create an issue.
As long as your incoming mains pressure is OK then you could ditch the shower pump - the age of the boiler makes no difference.
Moved into a house with solar panels on and have some questions if any one can help please? Owners left no details about the panels and invert but did transfer the FIT.
How do I calculate the size of the array we have? Will it say somewhere on the panels?
On the invert display it has a load random things which I have found some by Googling but not all any ideas/check my workings.
VAC = AC current of the main line
PAC = live output of the solar
IAC = ?? (Showing 2.6a)
IPV = ?? (Showing 2.1a)
VPV = ?? (Showing 378.5v)
E-total = ?? (I assume is what it has ever produced)
E-today = ?? (Today's generation total)
Thanks
Have a look at the inverter label/type. There should be a spec on it.
Without going up on roof and looking at the stickers if still there on the back of panels.....
The inverter will have a label on. It's unlikely your panels will be much less than that as the bigger the inverter the higher the start up current required.
An aside
I've had a new style hybrid installed to replace my non hybrid that's 18months old and it was old tech when I fitted it...
The new inverter (using same panels ) makes power at less light - reaches a larger peak and holds on longer into the dull light.
It's perfectly possible that folk with more modern kit than older kit could be making more than people perceive. The technology is advancing rapidly
Very interesting about the old Vs new inverts I assume this has been in since the original install back in Dec 2011
This is what's on the Inverter.
At a guess you've got a standard 3.6kWp (or is it 3.7?) system there.
Very interesting about the old Vs new inverts I assume this has been in since the original install back in Dec 2011
If it's that old don't touch it until it breaks as you're not allowed to make changes without losing your {substantial} FIT payments.
you’re not allowed to make changes without losing your {substantial} FIT payments.
Old news. They realised that they had people clinging in for dear life to outdated and undersized/under performing equipment because of the outdated rules. For the FIT payments.
who has solar thermal then ?
What panels do you have ?
I due to our area being classed as a colder climate - i believe i want evacuated tubes.
it seems that there are either very spendy seemingly inhouse mfg Viessemann vitosol /Kingspan thermomax options or - no name import stuff ..... evacuated tubes never really caught on here due to being visually horrible (although i quite like the steampunk appearance)
There's much more range available in the more visually appealing but much less efficient in low temp flat plate panels .... see Grant sahara kit.
Does any one have any real world experience of both (commercial stand alone safety approved systems) set ups and can comment ?
My fokes have them, not sure of the brand but ~10 year old evacuated tubes. Two panels, plumbed into lower coil on thermal store that is linked to wood burner. Works well for them.
Servicing is easy enough for someone with basic mechanical ability I have done a flush and a re-pressure with some simple home made set up. (Message me if you want photos / explation).
Biggest pain is occasional washing but you have to do this with solar PV as well if you have this problem.
There's a UK company called Naked Energy which do evacuated tubes, but that're filled with a small solar panels. this allows them to simultaneously create hot water and electricity at the same time.
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I'm currently crunching the numbers on a low grade heat augmented heat pump for our house heating to replace the gas boiler.
A heat pump has the highest CoP (Coefficient of Performance) at the lowest deltaT, ie it can move the most heat when it is "pumping" against the lowest thermal gradient. This means for an air sourced pump, on cold winter days when air temps are low, your heat pump is less efficient. However, on cold winter days, you can get some decent solar energy recovery (cold air temps are often also clear skys).
So the plan is to bury something like 2,000 litres of water in insulated IBCs in the garden, and use day time solar energy to slightly warm them up during the day, (or use cheap off peak 'lecy when tomorrow has a poor solar forecast). That slight warming is possible due to the large specific heat capacity of water (2000 litres stores 8,400 kJ/k, so small 10 degC deltaT to ambient stores 84MJ or justover 23 kWh) and the low deltaT and rules surface area to volume ratio (volume goes up by cube, but surface area only goes up by square). This "hot" water can them be used to drive a much better deltaT for the heat pump, maximising CoP. By storing low grade heat in water, the storage medium is about as cheap as it can be!
The other half joking asked if i could make that energy store in the form of a swimming pool....... 😉
Naked energy looks great
....except for the size and the fact theres zero data on cost or installers. - nor does it seem like it's been installed outside of the pilot schemes despite being a company since 2009 and a product since 2011.
But on the whole seems like it's for commercial grade applications with large flat roofs not residential
I'm pricing up EV chargers and PV+battery right now. Anyone got a zappi or hypervolt talking to their inverter for the clever solar integration functions?
Ideally I'd get the EV charger a few months before the PV, and possibly from different companies and am wondering who normally does the integration. First PV company says they wont interface to the EV charger, that's for the charger installer. I bet the charger people are about to tell me it's the PV installer's responsibility.
Anyone know if that's right and been through this aspect, or know how much is involved? Maybe just a data cable and some settings?
Probably going for a hypervolt charger if that matters. PV system is more of an unknown at present until i get the full quotes in.
So the plan is to bury something like 2,000 litres of water in insulated IBCs in the garden, and use day time solar energy to slightly warm them up during the day
The problem with that is that even on a clear sunny day (which are both short and not that common), you're probably not going to be generating much more than a third of the power required to raise that volume of water by 10°.
Interesting idea though.
Anyone know if that’s right and been through this aspect, or know how much is involved? Maybe just a data cable and some settings?
I think they're right, the charger people should set up everything the charger needs to do. I don't think there's really any communication between the charger and the inverter; the charger just measures what's going on at the grid supply to know whether it should speed up or slow down, the inverter isn't really involved.
Where it gets complicated is hybrid inverters; then the charger doesn't know if its power is coming from the PV, which it should use, or from the house battery, which it shouldn't. Zappi gets round this with what they call "export margin", so only charging when the exported power goes over a certain amount; this means the battery is full, and by keeping a bit of export going it ensures the house battery isn't being drained. I think it does mean you can't charge the car on PV in preference to the house battery, unless you can tell the inverter not to charge the house battery at certain times.
I don't know if hypervolt does something similar. Givenergy - the manufacturer of our inverter and battery - are releasing their own charger soon so maybe that will integrate properly for a bit more control. I've been very impressed by the givenergy dashboards, controls and monitoring.
I've been looking into this as our PV and battery was finished last week, but we only have a dumb charger. I've been managing charging on solar by using the granny cable at 2kw when there's a bit spare or the main charger with the car charging speed turned down a bit to 4kw when there's lots. It's a bit tedious, so I think a more intelligent charger is on the list for next year.
Ah right gotcha, thanks, that solves my charger fitting quandary then if there's no direct interface, i can see now that makes sense.
Just need to work out how much battery capacity to get, and whether i'm better off with a 3.6kW or 5kW inverter now. And whether the kit being quoted by my local installer is as good as the Givenergy stuff that seems to be the dogs doodahs (but seems tricky to get).
I thought I'd put this on this thread but it must have been on another one so (and please forgive me if I am repeating myself).
We have gone for renewables in a big way. No mains gas and when we bought our house 10 years ago it was a coal filled multifuel stove with a backburner for heating and hot water. The house also had a solar thermal system that had been installed in 1994.
Things we have done:
1. Biomass boiler - great bit of kit but pellets are annoyingly hard at the moment and does need love in terms of servicing and clean out. Converted house from vented to unvented tank too.
2. Updated the solar thermal - new microcontrollers and regular fluid replacement. Ours are evacuated tubes with metal vanes sealed in them, but are not made anymore. 30 tubes on the roof and work brilliantly.
3. 2kw PV on the boiler shed roof 8 years ago with associated FIT tariff. Over the 8 years they have reliably produced 1500 units/year or so. No optimisers on them as they weren't a thing back then. Shed roof is dead south facing at 20 degrees. we installed a Solar iBoost with this to top up the hot water when we are producing excess electricity.
4. This summer the south roof of our house needed re-tiling so we put 5.4kw of flush fitted PV panels on it instead of tiles. Its south facing at about 40 degrees. We also added a 15KW Huawei battery. This has been 'live' for the last 2 weeks and our electricity use has plummeted to an average of <2 units from the grid/day. This is when we try to draw more amps than the battery can supply (eg induction hob on, oven on and tumble dryer running).
5. We have also fitted a Zappi in advance of an EV arriving when its built and shipped.
Company used over the last 8/9 years are Energy Zone in Cleobury Mortimer so good for whoever it was who needed a Worcestershire installer! They are good but always busy.
Things I would say from our experience:
1. The biomass now that pellets are becoming harder to source. I think I would go air source (though this was less good 8 years ago).
2. Servicing renewable tech is harder to achieve than standard heating as there are fewer trained people to use.
3. Installers and companies do frequently go bust. Loads of biomass firms have disappeared.
4. Make sure the heat calcs are done well to avoid disappointment!
5. Consider 'air to air' air source - can be reversed in the summer to give cooling.
6. Solar hot water is very good in our experience.
7. Love the battery so far.
Hope this helps.
Just need to work out how much battery capacity to get, and whether i’m better off with a 3.6kW or 5kW inverter now.
I did some maths using the PVGIS online stuff to try to work out the effect of having a 3.6kw or 5kw inverter with an 8kwp array; there's not really much in it. The vast majority of the time you'll be getting less than 3.6kw off the array anyway, and when it does go above this it'll be on a sunny day when you'll generate more than you can use anyway. Also note that if you have a hybrid inverter with a DC connected battery the 3.6kw limit is just what it can convert to AC, it can still store excess above that in the battery. The givenergy 5kw inverter for example can output 5kw AC but accept 6.5kw from the panels if the battery can take the remainder.
That said, a larger inverter does give you more headroom to run larger loads from solar on sunny days (not necessarily from the battery - the givenergy battery can only output 2.6kw whatever the inverter), so assuming it's not that much more expensive you might as well.
We’ve had our array installed for almost a month, but still can’t switch it on as SSEN haven’t got around to allowing our G99 cert to be approved. When I call, it goes straight to messaging, when I email, I get nothing. What a bunch of clowns. Almost a month of free power lost to utter ****wittery.
Best hope they allow it then as g99 is supposed to be approved prior to install not like g98.
Can take 6 months.
Was looking at the data from first 11 days of the month .
1-11 Oct 2020 130kw used (no solar)
1-11 Oct 2021 66kw used (4.14kw panels)
1-11 Oct 2022 25kw used (same panels plus 10kwh batteries)
Most of that has been the electric shower so that's why I'm looking at the solar thermal and tank
Best hope they allow it then as g99 is supposed to be approved prior to install
This!
G99 absolutely necessary prior approval before installation.
I wonder if you could fit a smaller inverter (maybe s/h) to get going now and then change the inverter when the approval Congress through?
I also wonder how many >4kw
systems have been fitted that don't have permission!
also wonder how many >4kw
systems have been fitted that don’t have permission!
Lots . Just have to pop on to one of the many DIY solar groups on facebook Given the red tape they are making you jump through and making you use MCs (total racket) accredited installers with no other way round it. The backfeed rate is so derisory people are not bothering with it ....
That said I did get my smart meter read a few weeks back as they had "detected erroneous usage" ..... I read into that they didn't believe my usage had cut by half ...
MCs (total racket)
Like most of these schemes they binfit the scheme providers and the larger companies to increase barriers to entry.
The vast majority of the time you’ll be getting less than 3.6kw off the array anyway, and when it does go above this it’ll be on a sunny day when you’ll generate more than you can use anyway.
Agree although its important to do all the calcs yourself they are quite unique to each household. We have a 5.6kW PV and an 8.7kW battery on order. Wife works from home and I am retired so around most of the day. Intend to use as much as we need during the day then once battery topped up send the rest to our Immersion tank via an iBoost solar diverter. Any spare after that goes to the grid until we get an EV then into our Zappi as our EV will mainly be on the drive. We are with Octopus already so intend to go to their overnight tariff and top up the battery during the cheaper hours.
Waiting for our survey and to ask questions as to how configurable all of this is and how the separate components work with each other.
Just remember the bigger the inverter the bigger the start up current required from the panels.
I went from an old gen 3.6 to a current gen hybrid and I generate at much lower light level.
I've just been going through the calculations for potentially getting solar panels for our house. It seems to me that the recommended size of system recommended for a typical 3 bed house (3-4 kW) are flawed and based on typical energy use for an entire day. However, unless you are storing excess energy with batteries (expensive) or using it to charge an EV for example, then the most efficient thing to do would be to size the system based on how much energy you typically use per hour during sunshine hours. Any excess that you generate from an oversized system gets very little back from feed in tariffs compared with what you save on actual usage (and obviously costs lots more to install).
We use approx 10-12kWh per day - so ~0.5KW per hour. It seems like a ~1kW solar array (producing 1kW energy per hour) would be more than enough to directly provide the power that I would need to run appliances during the day.
Or am I missing something?
It seems like a ~1kW solar array (producing 1kW energy per hour) would be more than enough to directly provide the power that I would need to run appliances during the day.
You are right in terms of your daily usage apportioned evenly through the day but when you use power 1kW is unlikely to be enough. Many appliance use more than that, Toaster/Dishwasher/Washing machine etc so you are likely to be using your 12kW per in day in bursts. If you go over the 1kW then at that point you will be drawing from the grid unless you have a battery that can deal with the surge.
If you size panels to your use. Your reliant on the panels producing max all day long.
Need redundancy.
I have a 4kw array and even on the dullest of days I cover my static demand and only pay for my active use.
When it's bright the batteries get charged. And allow me to run the power heavy things free. Previously the panels only ever subsidised and it was impossible to use 100% of power generated without using more electric than intended.
Good luck with that thought process, what are you going to do when sun doesn't shine or at night?
5.3 array and 2 x 5kwh batteries, even on good days spikes in demand, electric shower oven etc mean we draw from grid,.
My washing machine uses ~0.5kWh per cycle (as does the dishwasher), so if I used these only during the day, they might be mostly covered by the solar energy generation (from a ~1kW system), I understand that peak energy consumption for the washing machine might be 2000watts, so this would need to draw from the grid.
As you say, a bigger system would produce more background generation on less than ideal days, but would cost a lot more to install, and the payback would take longer. Just trying to understand what we might need - I'm not prepared to pay the extra for battery, but can see that this is the answer to the problem of excess energy production.
Cost is largely access and labour.
1 inverter costs x
Purchase of 1 panel is 200 quid . 10 panels is 2000 . But your inverter /labour and access on either system is 3 or 4 grand
As a proportion of the install adding more panels is not massive given the cost of the rest of the kit given the benifits it brings and over its lifetime
Also, most of our energy use must come in the evening (electric oven, tv, Kids xbox, lights etc) when the solar energy generation isn't optimal, so my estimate of 0.5Kw per hour during the day is probably on the high side (except when washing machine or dishwasher are on).
That’s why batteries although pricy make so much sense…
My washing machine uses ~0.5kWh per cycle (as does the dishwasher), so if I used these only during the day, they might be mostly covered by the solar energy generation (from a ~1kW system), I understand that peak energy consumption for the washing machine might be 2000watts, so this would need to draw from the grid.
As you say, a bigger system would produce more background generation on less than ideal days, but would cost a lot more to install, and the payback would take longer. Just trying to understand what we might need – I’m not prepared to pay the extra for battery, but can see that this is the answer to the problem of excess energy production
I'll not repeat what others have said, but you'll be VERY disappointed if you go ahead and have a 1kW system installed (3 panels, you're wasting your time and money). The 1kW is the theoretical maximum, it will never generate that even when conditions are perfect (best conditions are cold sunny days, efficiency drops off the warmer the weather). Peak generation is when the sun is highest and tails off either side of that.
With a 4.2kW system the best days of summer we generate 30kWh, best days of winter 6kWh, however last December we generated a measly 52kWh for the whole month, 15 days were below 500Wh.
Biggest regret with our system? We only had 4.2kW of panels fitted, in hindsight we should have covered the roof, that would have given us a theoretical max of 12kW.
Also, most of our energy use must come in the evening (electric oven, tv, Kids xbox, lights etc) when the solar energy generation isn’t optimal, so my estimate of 0.5Kw per hour during the day is probably on the high side (except when washing machine or dishwasher are on).
In that case don't have solar installed unless you're fitting a battery too to utilise the generation.
We generate 4000kWh a year and use 35% of that, but that's because Mrs f is at home all day so the dishwasher, washing machine, oven etc are used during the day to make the most of the energy we generate
I suppose I'm trying to justify to myself that a ~1kW system would be useful! The problem for us is that although we have an ideal roof aspect (south facing), it is a shared roof with our upstairs neighbour (flat). This is Edinburgh - so common to have a groundfloor flat (us) and upstairs flat. So my understanding is that we would have to draw up a legal agreement for future maintenance responsibilities and change the deeds to reflect this. Although not impossible, this would add to the expense etc. Our upstairs neighbours are elderly (80+) and don't want to install solar themselves (they also worry a lot...).
We do, however, also have a single story extension with a flat roof that could accommodate 3-4 panels (so maybe 1600 watt max with 400w panels). I was just seeing whether this is a good idea with my calculations. Access and installation costs might be lower for the flat roof I guess (although would need some kind of racking)
That said, a larger inverter does give you more headroom to run larger loads from solar on sunny days (not necessarily from the battery – the givenergy battery can only output 2.6kw whatever the inverter), so assuming it’s not that much more expensive you might as well.
Thanks @phiiiiil , £300 difference for 5k inverter, sounding like a good idea then assuming it's ok with the DNO. I'll estimate how often I'd be using more than 3.6kW + max battery discharge rate. If I can get the panels I prefer I might be able to fit 16 panels so 6.48kWp. Time for more PVGIS calcs.
Consider if you have multiple roofs - you can extend your solar day for a significant part of the year with east or west or even north (for 3 or 4 months anyway) and that longer solar day is more useful (to me anyway) than peak solar output
3.6kW was quoted £7000 including £1000 scaffolding for our house, and 7.3kW £9000 including £1000 scaffolding.
100% more capacity added 28% to the price. Though you do need a G99 export agreement.
Guess what we went for?
@sparky1uk We have a Zappi, it came with a 'Hub' which plugs into your router and a 'Harvi' which is a small collar that fits round your mains cable and a module that communicates with the Hub and thus to the Zappi. The Harvi measures the power drawn or exported back to the mains. There's a phone app that links to the Hub on which you can see how much you're exporting and decide if you want to charge the EV. Our EV requires at least 1.4kW to charge, which I think is standard for EVs. The Zappi has 3 settings, Eco+ which will only charge if there's at least 1.4kW going spare, and so cuts in and out as clouds pass over, Eco which charges at the higher of 1.4kW or the amount of spare, or Max which is a flat 7kW. I tend to use Eco, and switch off if the sun goes in. The Zappi works as designed on Eco+, but after the first few cycles of on/off, our EV (a VW) gets fed up with being messed about and stops accepting charge, so it has to be unplugged and plugged in again to reset it. It would be nice to just leave it on Eco+, and hopefully there will be software upgrades that fix the issue.
My washing machine uses ~0.5kWh per cycle
Cold wash, presumably?
I considered a Zappi but decided that the £900+ installation cost (you also need the Harvi wireless transmitter) would pay for a lot of electricity. With a battery installation and a sunny day, I just limit the car to 10A between 9am-4pm, with unrestricted charging in the cheap overnight period. If a cloud drifts over the panels then the battery picks up the difference and recharges once it brightens up again.
So far I’ve not troubled the grid during the peak hours, although with an electric hob I would say that I’ve developed a tendency to cook steaks slightly rarer than I used to because you literally watch the battery emptying itself expensively in front of you while cooking.
Thanks for the info @Greybeard. Ours will be a cupra born, based on the ID3 so maybe have the same bug. Do you have a battery on the PV? Sounds like that can add another layer of control/complexity, with export (or charging in my case) directly from solar only after the battery is full.
Do you have a battery on the PV?
No. We use about half what we generate, on average in summer, and I suspect we'll use a higher percentage in winter, and at times in summer we'd fill the battery. I calculated payback at about 23 years. I'd rather spend money on more panels, which are an overall environmental benefit. A battery is just a financial benefit to us, it doesn't do anything for the planet.
My washing machine uses ~0.5kWh per cycle
Cold wash, presumably?
No, 30C wash but speedy cycle. Measured with a power meter.
Looking at what uses power on the various graphs our system provides, our normal washing machine cycle uses just less then 0.5kwh and the dishwasher just over 1kwh, but both use most of that in a short period when they go up to 2.5kw. It would need a fairly large system to be able to provide that on anything but a super sunny day.
including £1000 scaffolding for our house
Is there a reason why scaffolding seems to vary so much? Quite a lot of houses round here have gained solar panels this year; some have had proper huge scaffolding erections put up, often for extended periods of time, but others - including ours - were done just using a mobile scaffold tower that took no time at all to build and take down and must have been an awful lot cheaper.
A battery is just a financial benefit to us, it doesn’t do anything for the planet.
Not quite true. The battery allows time shifting of demand, meaning that generation resources outside the home as well as inside the home can be better utilised.
That means that for a given energy use less aggregate nameplate capacity of generation is needed - that is a benefit to the planet, and it is particularly true with variable generation like wind and solar where you harvest the energy into a battery when you can to use when you need it. It is less true in a system with plenty of flexible (we used to call it dispatchable) generation like CCGTs. But hopefully that will change.
So is a battery an environmental a benefit in isolation? Possibly not. But in aggregate it is. Just let’s not get started on particular battery chemistries and characteristics - that’s where it gets hard.
A question about battery capacity and how much can be run from it.
I understand that Wh = Ah x V, so a 100Ah 12V battery can provide 1200Wh, but what happens when you convert your 12v DC battery power to 240v AC power with an inverter? Do you still only have 1200Wh or is it now Ah x 240v?
A battery is just a financial benefit to us, it doesn’t do anything for the planet.
Unless you dont consider the harnessing and use of electricity that would otherwise be lost a benefit to the planet.
Unless you dont consider the harnessing and use of electricity that would otherwise be lost a benefit to the planet
It's only lost if you don't have a single neighbor in you side of the transformer
It’s only lost if you don’t have a single neighbor in you side of the transformer
I dont know what that means
Do you have houses in your eyesight of your house ? If so your electricity did not vanish into thin air.
use of electricity that would otherwise be lost
It's not lost, it's exported to the grid, and I would be paid 3.95p/kWh for it. But IGM has a good point about a battery enabling time shifting, thanks.
It’s not lost, it’s exported to the grid,
I see.
I've asked two localish firms to quote for installing systems to our bungalow.
This is what they have come up with:
Firm one.
10 x 415w panels
1 x 3.6kW inverter
1 x 9.5kWH battery
£9940.75
Installed inc Vat
£11695
Firm two.
12 x 405w panels
1 x 3.6kW inverter
1 x 4.8kWH battery
£5860.00
Installed inc Vat
£9028.34
I intend to get at least one more quote but the two systems quoted aren't *that* dissimilar (on paper at least Firm two - battery size apart - seems 'better') but there's over £2600 difference in price. What am I missing?
The VAT on the 2ns quote doesnt seem correct?
The 2nd battery is double the 1st so looking at post VAT prices they appear very similar. Around £2667 for the additional 4.7kW.
I received 5 quotes (after approaching 6 companies) and other than one outlier, and considering they were all using different kit, they were broadly similar.
What am I missing?
Battery size.
A battery is just a financial benefit to us, it doesn’t do anything for the planet.
I think the battery is the real game changer for our system. The panels worked for a week or so before the battery did; looking at our usage over that time you can see it made a difference, but we just didn't really need much electricity while they were generating. Once the washer's been on a couple of times that's pretty much it. It maybe knocked 1kwh off our normal 6-7kwh daily total.
Once the battery was in though our import dropped like a very heavy stone, from about 5-7kwh a day to about 0.5kwh. We're lucky in that it's been a sunny October so far but it's covered all our usage as we can save it up and use it in the evening when we use most power but imported power is at its dirtiest. The only time we have needed to import anything has been when the load exceeds the maximum the battery can supply. When winter hits properly we'll fill the battery with off-peak electricity instead, which can be much cleaner than peak time electricity.
Wh is a unit of energy, so it's the same energy however it's delivered. 12V 100Ah or 240V 5Ah is the same - except the inverter isn't 100% efficient, so you lose some in the conversion, probably end up with between 4Ah and 4.5Ah.
That makes sense. I hadn't thought about the equivalent drop in Ah during the conversion.
The VAT on the 2ns quote doesnt seem correct?
Renewables are zero vat rated now which includes the battery if its bought with panels.
Firm one.
10 x 415w panels
1 x 3.6kW inverter
1 x 9.5kWH battery
£9940.75
Installed inc Vat
£11695Firm two.
12 x 405w panels
1 x 3.6kW inverter
1 x 4.8kWH battery
£5860.00
Installed inc Vat
£9028.34
As said there is zero vat on renewables.
what panels, inverter battery? if you want seg payments are they MCS reg?
what is your average usage?
If you can max out roof area and get a big a battery as you can.
Why is firm one only fitting 10 when firm two fitting 12? Ask firm one to fit 12. Do checks on companies house on firms to see how long been on the go and local reviews on either etc etc. check check and check, lots of 🤠out there just now
