How to size a home storage battery 

Great video, nice to hear the considerations from an end user rather than a salesman with a vested interest.

Thanks, Nigel. Some good ideas to help with the calculations. Great work, keep it up 👍👍 I am 1 week in to having Solar connected. It's an E/W facing roof on a smaller detached house. I've gone for 12 West facing and 7 East facing panels - All I could fit given the roof shape. On Monday we have a 5KWh battery arriving. Looking forward to seeing how this helps with the overall aim of reducing pull from the grid. I will use this winter and spring to see how it works, and consider adding another 5KWh battery next year. I remember your earlier video well with advice about just using less electricity first before buying batteries. We only use 2750KWh a year at the moment as a household, but well see how this changes as we adapt to having the solar / battery available.

I think for me a key consideration as well is future proofing. I’ve gone for bigger than I need with the expectation of buying an EV (or 2) in future and possibly a heat pump further down the line. Seems like more and more things are going to be using electric going forward.

Morning New to this game, had 12xJA Solar 405w panels, a Solis 3.6kw hybrid inverter and 2x 5kw PureDrive batteries installed early August, so not much data yet…so far, I’ve only imported 49kwh (approx 6% of my consumption) since the system went live and living in the central belt of Scotland I’m expecting this to increase over the winter months…more to follow as my data set expands… Like the videos….

Good video as always. I have to agree, sizing of the battery is a case by case basis. When I started looking back in 2019, my primary goal was to be able to get through the evening and so I went for a 16kwh system. Now with electricity prices as they are, getting through a dull day on the cheapest electricity available has become the priority, hence shifting from 21kwh usable to 25kwh , the extra 4 is to balance things on those dark days. Being able to charge cars or hear water and run the house without pulling from the grid at expensive times has proven to be invaluable. The install I have can cope with 7.2kw of load, which with the 10kw solar can mean covering a 10kw of load (7 from battery, 3 from solar) on an october day. So as you have said, this is about what is needed for your case, and one size does not fit all.

Thanks. We just had solar panels installed Wednesday and now looking at batteries.

So I've already got 106kwh of batteries sitting on my drive (Ioniq 5 and Peugeot e2008 - soon to be an MG4) and one of them is usually always plugged in during the day. That said Myenergi's new Libbi looks mighty tempting...

Excellent and though provoking video - thanks for your efforts. For those with an EV, keeping spare capacity in the car is very useful especially given that car battery sizes can be far larger than permanent domestic storage. How long before most cars become a fully integrated part of our grid balancing system?

i went from 4 x us3000c pylons to 6 x us3000 pylons and went with a parallel 5000va multiplus so I can charge in the four hour window, because as you say a single victron wont do it. Great thing now is that I can invert up around 7500kw - which means whatever I have running in the house, i never pull from grid. Crucial thing is a use multiple jump cables from the pylons because they too thin (25mm2) to support sustained high current. I use a jump cable for each pair of pylon 3000’s and it all stays cool now

Thank you for your video. You bring up some interesting points.. that being said. I simply disagree about your charge that we need to use less energy. If we're talking about energy from the grid I am in complete agreement. However, one of the biggest advantages of even having a solar installation is the freedom to use energy to enhance our lives. If one's system is properly sized energy usage no longer impacts the grid. Obviously, it's not practical to design a system that will be 100% grid independent 100% of the time for days and weeks on end, so airing on the side of caution is always wise. I SAY: " LET SOLAR POWER SET YOU FREE!"

I've had 9.9 kw DC battery storage and 6.8kw solar for 18 months and recently added a further 3.3kw. As a Go customer if you charge your battery at night you can only charge at 3kw so at most I can only charge 12kw at the lowest cost. So any more battery storage could only be charged at full cost. I found on the worst solar days with 9.9 I would sometimes drain the batteries towards early evening. Though managed an average of 6.08 pence per kilowatt cost most of last winter. Batteries are great during winter using low cost night charging when solar is low but if you have solar the batteries hardly ever get used during summer months so usually stay over 70% charge with 100% most of the day when the suns up. No need for any low cost charging during the summer. Not sure of the charging speed of ac batteries.

Yesterday, Tesla support gave me the option in my app to import/export to powerwalls, as opposed to only using them in support of solar. Very excited to see what difference that will make financially, as it dumped 29 kWh into the grid last night as soon as peak arrived. If we charge at .07 and export at .22, something tells me it won't be as simple as just multiplying the difference.

We use less than 10kWh/day on average, and we're retired. We've just had 10kW of panels installed 5/5 on an East/West roof with a 35° pitch. Two 5kW string inverters and an Eddi. I also have a Zappi, but only need to charge the car once a fortnight, if that. I've turned off the gas hot water and use appliances as much as possible during daylight hours. I have a 10kWh Libbi with 5kW charger/inverter on back order (subject to price). One of the issues that needs to be considered is battery inverter. Microwave (900w) plus kettle (2.8kw) plus oven (2.5kW - 4kWh on boost) means that a 3.5kW battery inverter won't hack it. This is going to be a learning experience for me between now and when the battery arrives.

Would have been helpful to know the size/age of your house, and # of peeps in house. Txs. You brought up some very astute points (like the EV pre-charge) - and the urge to conserve!

Great video, as usual, I had 3x Pylontech US3000C's installed when my panels and inverter were installed BUT, I've just bought 3x US5000's to join the 3000's, giving me around 23kWh. My 8.5kWp array may not be able to charge the batteries fully during the winter (unknown since only having them installed in March) but top that off with Agile and I should be good. I've started testing a couple of infrared panel heaters, my wife loves the one under her desk and I have a 720W one in the conservatory which I'll use when the temps drop enough.

I would love to know more about your pylontech battery choice esp as you have looked at quite a few. Very useful vid on battery sizing thankyou

Other considerations to consider lowering your electricity usage, and depending on where you reside. Is the use of Tankless water heaters, or using natural gas/propane to heat your water and heat your home as well as to cook with. Here in Texas. I am use a propane tankless water heater, and my central heating is running off propane. Propane is cheap in Texas. However, the issue we have is the A/C usage in the summer. While our u it is on, it draws 5kw as long as it’s on. We also use a propane generator to charge batteries in prolonged bad weather. Where the bad weather has knocked out the power grid. I use propane to off load electric use to allow for smaller batteries and less panels. I use around 6000 kWh per month.

Thanks for posting. Great video. Having a 4kw stand alone system with 9.6kw of battery and it’s being fitted in the next few days. I already have a 1.8kw system 11 years old giving me maximum price on feed in tariff. That’s having a new inverter and replacement panels. The 9.6kw batteries were a guess. I’m considering adding a 4.6kw battery to my 1.8kw system also. Going to start recording how much I’m generating on the existing and the new system then will decide where to go next. But this video will save much head scratching. John

Don't know if you have already said, the flexibility of having a battery/size for running a load when the sun is intermittent to keeping a high KWH item running while keeping you off the expensive grid tariffs is useful

I do this on an outlet basis. Started with my kitchen as that is the main area that needs to continue to run when grid is down. Testing my need is a matter of turning of the grid for as long as I can deal with it :-) I started in my kitchen using an Ecoflow River 600 with 768 wH inside and an extern 1500 wH external battery. It can run some bais appliances in my kitchen like a fridge and a inductionhub on lower settings. So I can heat some food and charge some small devices. If needed, it can also run the heater of my house which is on gas but does need up to 50 watt of electricity to do so. I charge it from AC but on a sunny day I turn that off to profit a bit from my solar. Only like two panels which is fine in grid down situations. These panels are also connected to a grid-tied-inverter so they are always able to dump their yield into my home grid. Using a 1-2-both switch on the MC4 solar cable to do this, also allowing me to send more to the battery's. Do mind the voltage that the mppt-charger can deal with though* Now for my kitchen I want some more wattage, so looking for the Delta 2 so I can run 1800 watt devices even when the grid is down and have some more storage. The old system will then just run the internet and my working at home spot, which one also want to keep alive when grid down. * I solved that problem by having a victron mppt charger that could deal with the voltage from the panels and have it charge a 12 volt battery. That MPPT-charger also has a load port that can be programmed for a certain voltage range of the battery to open up. To that port I have connected my Ecoflows in my home, so they only get charged from DC when there is enought voltage in the 12 volt battery.

Thanks, a good discussion. I just about manage with 7.5Kwh, but the payback of adding more is way too long, but I still wish I had gone for 10 Kwh. In summer, no problem, and surplus generation from my 4 Kwp is just dumped to my ev. In Winter, I fully charge the battery on the cheap overnight rate. Load shifting helps keep me going. I just about manage to keep my day rate grid unit cost to about 1 unit/day, but the savings from extra battery are way too long. Everyone is different. Heating is still gas, and living in a very old house, there is little chance of further gains.

In the winter, my solar production does not even cover my home use, so even a good 10kWh of solar would not provide energy for the home. I found my Tesla Powerwall 2 would top up overnight and be used during the day and evening, helped by any solar production. I found my night use of the cheaper tariff was at 89% so it certainly saves a lot of money if used correctly. Also in your calculation you stated your solar equalled the size of your battery, but it must be remembered the home will be consuming some of that solar energy!

We're all different, but I found some of the points in this video very theoretical. I have an ASHP, underfloor heating, electric vehicle charged on a home wall box, 6.4kW solar, and 13.5kWh Tesla battery. No gas or oil. Most winter days in our 4 bed 2021 build detached we consume about 50kWh, 60kWh when the average 24 hour temperature is down to 1 or 2°C (or lower), about 40kWh when it gets above 5°C. In winter, the solar output is pathetic, about 2 to 3 kWh per day in December. So we charge the Tesla domestic battery overnight on Octopus Go off peak (which lasts 4 hours) at about 3.5kWh per hour. We also run the underfloor downstairs heating fully during off peak, and the ASHP can run at up to 3.8kW to achieve that (especially in sub zero temperatures). The wallbox for the car charging consumes 7.5kW, and other demands (electric heating in the bathroom, for example) lift our overall consumption to about 15kW per hour in the off-peak period. That is about 70amps, so the first point to check is the actual fuse size for your electricity supply. The box probably says 100amps on the outside, but the District Network Operator may have installed a smaller fuse because of local network inhibitors. For about 120 days of the year in winter, we could use two Tesla batteries. That would allow us to get an additional 11kWh of usable off peak capacity (Tesla recommends not depleting the battery below 20%), so on our current tariff that would enable savings of (40p full rate - 12p off peak per kWh) = 28p per kWh x 11kWh per day x 120 days = £369 per year. On current prices, that's a payback period of 20 years +, which is longer than the lifespan of the battery, and we would need a 20kW supply. In summer, our daily usage, excluding car charging, can often fall below 20kWh. So we only need one 13.5kWh battery to cover evening use after the solar has stopped. We charge the EV either from overnight off peak or trickle charge from solar (in summer). In an ideal scenario, we would probably have about 15/16kWh of USEABLE battery storage, but since Tesla only makes one size of battery.... As the video says, we're all different. You might want to run air conditioning during summer days, or you might want to keep a reserve to cover for external power cuts. I would never seek to charge an EV from a domestic battery, because in many cases you might be putting the charge through two inverters, one into the domestic battery, and one into the car battery, with a loss of about 10% each time the supply is fed through an inverter.

Partly why I've gone with the Pylontech batteries (& your recommendation), as not sure what the solar will generate (install of both in November) against our usage. Heating/water still has, so daily usage not that high. Will see how it goes and add additional batteries if required. The solar install is the expensive thing (~20% of our cost is scaffolding) so get as much of that as you can when first doing it. The other bits are easier to upgrade or add to

Thank you, nice overview very helpful.

Tricky as we charge two vans every night plus we are heavy users. Our lowest daily load may be around 20kw but typically 60-70kw. Trying to install a big enough battery to cover this would be uneconomical. The annoying thing is we have 100kw of batteries sitting in our drive but no vehicle to home functionality

It also depends where in the UK you live as some parts will get more sunlight / sunny days. I had a quote for a 6kW solar array plus 3kw battery at a cost of £12k (£1k for EV charger on top). The issue I see is that in the summer I can't use the 36kwh I will potentially produce per day as the rear roof of my house faces due south. The national grid pays more during high demand which is actually in the winter when its not so sunny. I am considering a 2.4kw array at ground level (on a shed roof 6 x 400w panels) with a 5kwh battery and 3.6kw inverter. I want to power a home office and charge / top up my EV using the 13A charger as it can charge at 2.4kw easily. My car isn't my main vehicle as I use a van for work so car can sit charging 7 hours a day. Do I apply for G99 and grid tie the inverter or simply add a change over switch in the home office to run of solar system or from the house ?

One important factor I'm not sure you covered (if you did I missed it) is that the battery might be say 10kW capacity, however since you very rarely would run it till it's flat and battery makers usually suggest only charging to 80% to help them last longer, that means that although rated to 10kW, it's more realistically like 7kW of usable storage, so as someone else in the comments suggested I would say you're better off doing your numbers, then going 1.5 times the size to cover the charge capacity and also degredation over time which will also reduce capacity.

When vehicle to house, and vehicle to grid charge points are available for the public to buy in the UK, that will make pence per kWh a lot more affordable. I am looking at buying a salvage Leaf with 24kwh battery for just £1000, even if the battery is only half the health, it works out about £80/KWh, instead of the home battery at £800/KWh!

One thing not mentioned is look at the output power of the battery, a small one will not be able to fully provide the power for a kettle for example, somewhere around 5kW is fine for most people, this requires a larger battery, as you have done, think big!

I installed PV and battery so that I can carryon as I am - just at a cheaper price.

I have 8.2 battery I was thinking of getting another one but looking at quotes it will be more cost effective to add more panels another inverter and battery also it I will be able discharge at higher rate

Have really enjoyed your videos. Taught me so much. I think I've worked out now that a 6.5kw is the right size for my usage (not the 3kw my 1st quote was for). This allows me to expand later if I need to. Trouble is, can't get anyone to quote or stocks are gone. I'm ready to go Solar PV + battery, but no-one available to service me. Frustrating, but now I'm thinking I buy the equipment & hang tight till I can find a fitter.

Great explanation 👏

very well explained sir...

Hi Nigel. I really liked your battery size video and have just subscribed to your channel. I'm researching quotes for a Solar panel veranda + roof panels + battery + EV charge point up at West Runton. Can you recommend an installer? BTW have a large GSHP fitted last December to replace the Calor Gas boiler - much cheaper. But it ruins your garden!!!

very helpful breakdown - thanks,

handy video..! what about dynamic ess? mine is a victron instalation of 4kwh solar and at the moment a 5kwh battery, my coverter is 5kwh and i am using 6kwh a day in the summer and same as you, 24kwh in wintertime..so i need to get to what size battery? and is it possible to disconnect batteries in the summertime to expand the lifetime of the batteries? cause in wintertime i charge them in the night when dynamic prizes are at there lowest and there is no sun.

Another informative video Nigel. I may of missed it but I don't think you mentioned the degradation over the life of the batteries. E.g if it was 20% over 10 years then a 10kWh system will only hold 8kWh. So if the need was for 10kWh then one needs to add 25% = 12.5kWh. I know the % is stated by the manufacturer but I suspect the manufacturer's % are derived through stress testing and extrapolation and will vary by manufacture and that the reality maybe better or worse than expected. EVs have proved less that had been feared but they may be less stress than a home battery system.

it's all very well sizing the battery, but to get that size has to make financial sense surely, especially if or when paid for exporting back to the grid. I bought 200Ah cells from AliExpress. So about £1k for 10kWh of battery. Another £200 for a Seplos BMS. That just about makes sense financially, but many batteries are £1k per 2.5kWh, which I cannot see being financially viable

Thanks for your content Nigel. I'm currently researching the best option for my NZ passive house. My latest thought is going for the Tesla Powerwall mainly so I can one day join the Tesla Energy Plan which I hear has great returns compared to the normal 12-17c NZ per kwh. What are your thoughts on the Tesla Energy Plan?

do you have pylon batterys.. how many do you have on your setup. i have 4 of h48050 2.4KW for my Solax X3 5kw setup. but we have heatpumpe air/water and used in October to febuar about 40KW pr. day. mostly is for the heat pump that are using about 30kw. alone

Hi, Your videos are fantastic, thank you so much. Just got lost on your logic here. Dec 21 you stated you generated 94kwh for the month and 250kwh in Jan 22. I think this is on a 5.8kw system before you upgraded. This averages about 10kw per day over the 2 months, no problem. However in Dec 21 you averaged just 3kwh per day ( say upto 4kwh per day with the increased size of 9.3kw), so how are you saying your solar plus 18kw of batteries will cover your usage of 24kwh? Am I missing something? I live in Norwich and currently since system went in 20/12/2022 average about 2kwh per day on 5.8kw panels, it can only get better?

How much will 2 extra batteries cost with installation?

I don’t have solar as yet but want to take advantage of the overnight Octopus low rate. I’m going to use Pylontech batteries. How do I work out the number of batteries and inverters ?

The biggest issue I have is that my home uses 500W/h nominally and there are a few peaks of around 30minutes to an hour of 9kW when the shower is in use (stepson uses it way too long) or the microwave/toaster with 3kW each I have solar panels of 3kWh MAX but the inverters do not run high enough for the max loads. Instead of the 500-700W average.

Great video. Lots of info. I'm like you I've gone a bit OTT. But u really utilise the Go tarriff. I would be interested to know how you manage you night charging? Do you look at Solar data for the following day? Or do you just charge at max amps every night?

Battery I would love a battery but they can’t get my system finished yet still waiting for the inverter to get installed, the price of the battery will soon get ridiculous and they get greedy and start pushing prices up. I’m off of the battery wagon for a while now 😢. On a side note did you get the Shelly installed?

So just done a calculation on how much electric I’d need instead of oil…turns out we are using over equivalent 15000kWh of oil! Would converting this to electric even be possible in medium size house?! Plus we use 5000kWh of electric per year. So I calculate to get solar to cover this we need a 20kWH array the works at full capacity 2-3 hours ‘every’ day! In Wales is that even possible! Even if oil quadrupled in price which I think it will…it seems oil would still be cheaper over next 10 years compared to buying batteries, panels install etc?!

Tesla powerwall is 5 kw charge and discharge nigel, ❤

Thanks, very usefull video !! A Quick Compare : SOK or Pylontech US5000 battery rack 5kWh , which is the better ? An advice ? (Prices are very close)

Just a thought for the folks that are concerned about the planet. How about using batteries that are not based on Li. There are a number of possibilities. Using Li for static applications is driving up the price due to supply and demand and making EVs unafordable to many of us. And alternated technologies, while the don't have quite the cycle efficiency of Li batteries, have much much greater lifetimes.

Have you given any thought to a minimum SOC in case of a power cut?

When you say not to oversize, I have build 48kWh battery from2x 2015 nissan leaf 24kWh batteries. i only intended to use one 24kWh battery but when offered a second battery I couldnt say no!

Hello, Nigel; Do you happen to know if it is possible to add home batteries systems from different company's? For example, could you now add a Tesla PW into your system! I know you research these thisgs to great depth, amd wondered if you have looked into this at all, it's a bit beyond me to do so. I currantly have a SolaX 10kWh pack, and want to increase the capacity, but I think my installer may have stopped trading, as I'm getting no replies. Thank you for taking the time to read this. ...........Soryy, the reason is I want to delete gas, and fit an electric heating only boiler, I want to store 20kWh of over night rate electricity, and use this for heating. Thank you for all the info you supply.

i recently saw a post on FB that showed a US2000 that had burst. its put me off them a bit to be honest, that and the fact im struggling to find any installers that either recommend them or will install them. they all seem to want to use Gro watt, Giv energy, etc. also how long do think before prices return to the correct levels? i had a Giv 8.2Kwh on order back in Jan 2022, installer could never get any stock so gave up in April, that was £4k with vat, as no solar on it as have a 4kwp already.

How big your inverter for all your system or you have multiple inverters?

I see what you mean about the GX module. Another thing: have you looked at wiring a switch to automatically change from grid to inverter in case of power cuts? It seems automated products are very pricey for what they are, whereas a beefy 4-pole contactor in a nice box is under £200. Would such a switch work with your inverter charger?

As off grid, which I know you don't really talk about... (and I'm doing that coz i like diy and avoiding bureaucrats) then the bat is the best way to soak up excess solar.

Great video. I thought the PW charged at 5kwh though? Hopefully get mine within the next few weeks. Been on order since Feb!

Thanks Nigel. going back a few vids can I ask (we've got a 5kw Huawei Fusion inverter) been looking at Luna's. How did you get on with that 5kWh battery you had on loan. looking at possible going for the 10kWh (2x5kWh)

Size matters

A word to the wise. Some buildings insurance does not cover panels...

Couldn’t you just start with 5kwh system and add ass needed. Seems like a lot of systems are easy enough add to?

kilowatt hours meant nearly nothing to me, Amp Hours is the main issue. I calculate 25,000 for my basic needs per month.

As per the hot water thing Its far cheaper to store hot water than store electrical energy So, add more hot water cylinders... They are cheap.

Hear me out here please - Lets say IF you could run a generator off hydrogen : Have you ever thought of how you could charge those pylontechs during winter ? with say a genny that was basically really really cheap to run and kept somewhere where it would not be heard ? would you/could you and if it was doable how would you make the connection to the batteries so it all went through the houses fuse board - all done safe, ive seen it done in the US but not here in the UK - Well not with a domestic dwelling

"...clean energy. .." - True, shame about the cobalt and lithium!

My system 5kw Solar Array (south) Sunsynk 3.6kw hybrid inverter (7kw mppt) max charging 90A @54.6v (4.9kw) 20kwh (4x 5kwh) Sunsynk BYD batteries. September Generation 368kwh Export 17kwh Import 6kwh yes... just 6kwh Utilita smart energy tariff. No standing charge but first 2 units are higher (was 52p/first 2 kwh, then 29p/kwh thereafter. Thats now 60.5p/first 2 kwh then 36p/kwh thereafter. So if I don't use the grid power... no standing charge. Total electricity bill for September 22 £3.60 Total gas bill for September 22 £18.39 Total monthly bill for a 2 bed flat (with solar panels in the garden) £22.99 My storage is overkill but it does compensate for poor days. I can go 2 poor (rainy) days before I get very low (into the 20% area) And if I know the weather is going to be bad... (december) and i have completely discharged the battery and already pulled.ppwer from the grid... i will do an 100% charge throughout the day so that for the next 2 days I won't use grid power and won't pay the standing charge for those days. I dont have SEG setup as some of this was DIY setup... however for the 10k it cost me, the ROI based on Generation at 36p/kwh is 100 months 8.3 years. But if I'm saving 2x 60.5p £1.21 a day standing charge for lets say 10 months of the year (300 days) thats an additional 49p/day saving (2x 60.5p - 2x 36p for the first 2 units) so a yearly saving if £147. That reduces the ROI on the 10k investment to 7.5 years. The system has only been online since sept 1st 2022, so using September Generation figures gives a rough mean/average for annual Generation and ROI. I'm sure this will make sense. I had the option of getting 20kwh of Storage for £6k and zero vat as the company installed the inverter at the same time. Solar panels were self installed.

I'm in the building phase. Already have 6 kilowatts of solar We use about 13,000 kWh averaging 36 kWh a day. I project that to go to 30,000 a year with a heat pump and 2 ev's Custom designed 83kWh of battery rackmount. Price per kilowatt £250 3x Victron quatro 15kva in 3 phase grid tide Victron MPPT for charging the batteries It's 11 kW. DC only 5.6 kWh more solar I plan to only charge to 90% and not discharge below 20% to maintain battery life. I plan to achieve 20 kw of solar Three EV chargers. A. Three-phase heat pump Some sort of heat seasonal storage. Still looking...

Bollix to green energy and peak periods. I’m more interested in getting my 300% increase in energy costs down. If that means burning apple cores, banana skins, newspapers etc in the fire like in the 60’s and 70’s then be it.

He said "bat-tree"...must be an English battery.

Excellent video. I started with 6.5 kw solar and 8.2 kwh battery and found battery running out during the day in the winter months. The battery is only 6kwhr useable so I have just topped up with a new 9.5 kwhr battery which is 100% useable giving me 15.5 kwhr. What a difference it has made with grid import down at below 1 kwhr per day this winter. I used to charge the battery overnight on cheap rate and whilst still having to do it when there is no solar, the frequency of charge has also reduced. I agree with going big on battery size and solar. The biggest surprise has been the free hot water from the EDDI. In 550 days of having solar I have used the gas boiler only 10 times to heat up the water!

Very useful video. I went through similar thought process and decided on a factor of 1.5 times average usage, so 15kwh battery for average usage of 10kwh. Only installed for a few months but seems to be working out. Definitely think about the three parts of the year. Summer - we will be self-sufficient in both electric and hot water - no mains usage. Winter - just charge the battery in the overnight cheap rate and let solar do what it can to cover daytime load and recharge. Spring/Summer- partially charge overnight and top up from solar. One big advantage of oversizing: if you are installing a complete system it is free of VAT, if you add an extra battery later it is plus VAT!

Thanks for a really useful video. While I understand people's obsession with payback times, the other thing to consider is the additional value you've put into your house. Should your ever sell your house you'll definitely get your investment back and make it more attractive to potential buyers. I mean, given a choice of two identical houses, one with an electricity bill of £3000+ per annum vs around £300 a year it's a no-brainer

Hi great video and very informative 👍. I've now fitted a Ac coupled giveenergy invert and 9kw battery although I'm struggling to get hold af a WiFi dongle unfortunately, any ideas where might still have them? My solar array has been great since it was switched on yesterday and the the weather has really been great. I believe we were exporting from 7.50am until sunset so am excited to get the battery commissioned.

Good stuff. Can you Island, run all your house if the grid goes down? or do you only have specific circuits that will run purely from battery/Solar power (I understand many solar systems will not function if the Grid supply goes down and many buyers do not know this or ask about it as they assume they can run their house on solar)

I need to know more...I am having real problems with my giv energy 5.2 kWh battery. It is only charging to 2.7kWh and they keep recalibrating it to try and "push" it into full capacity. I accepted their suggestion of going into the firmware fix experiment, but again, oh we need another calibration.. At what point should they give me a new battery

Thank you Nigel. Great advice to enable me to focus on my requirements. Reasonably straightforward now that you have broken down the process of recording the data to enable an effective decision.

Thanks Nigel, great video, so useful. I'm another Norfolk boy here! Aged 65 living in an old and cold Grade 2 listed farm house. Planners not keen on roor top solar. Probably not living in this house for a long time. EV arrives in a couple of months. Looking at batteries initially I "think" that solar will be more expensive if we have to do a barn roof install (East/West panels as ridge is North/South) = more panels plus the roof is not good. Field solar install I think might be more expensive due to cable runs of over 100m. Looking at batteries as being more transportable if we move. Then looking at Octopus Agile to shift daytime consumption into batteries, charging batteries at off peak along with EV. Whats this like as a plan? Ps subscribed!

I don't understand how payback cannot be the most important thing? That is except for people like me who live in a village that suffers from regular outtages so an off grid back-up has a practical value?

Absolutely the best DIY I've seen this week.

I'm a low power user typically taking 5-6 kWh/day. I went for a 3.16kW array & a 3.3 kWh battery. Had I known what I know now, I probably wouldn't have had it put in. The battery discharge limit is typically 2.2 kW. Put the kettle on first thing in the morning or put the oven on in the early evening & anything above 2.2 kW will automatically get drawn from the grid; that's even if the battery is full. Likewise, there are occasions when the battery just refuses to deliver current. In the wee hours, it seems to give up for maybe 15 minutes at a time & the base load (fridge, router, etc) all comes from the grid. Also when wifey uses her hairdryer, sometimes it refuses to play ball. It's really annoying when you're away on holiday & the system has virtually bugger all to do, that you see the system pull 0.7 kWh/day from the grid! Yes, money-wise this is no big deal, but when you're already a low user, it's not insignificant & totally undermines the overall economics of solar.

Good video, you are quite right with all the options at the end of the day it is about finding the solution which makes you feel most satisfied. This is a balance between what you can afford and what gives the optimum savings in returns and environmental benefits.

Dear Nigel, Your videos are so informative, thank you for sharing. I'm about to invest in storage batteries too. Possibly in combination with a Victron Hybrid inverter/charger like you are using. In several video's you mentioned that your batteries are charged either by excess solar or by importing from the grid at a low tariff. Is this selective charging done automatically or by daily manual settings in your Victron inverter/charger? Please explain about how you manage this and were you found information on how to program the Victron inverter/charger or other device that controls the charging behavior of the Victron. As you mentioned in one of your video's some time ago you would prefer this intelligence in the battery solution what was not (yet) available at the time of recording of that specific video. I would like to have this automated if possible by means of scripting in smart home automation like Homey Pro. P.s.I already have a Solaredge inverter plus 14 kWp solar panels. A Zappi EV charger is also running here ;-) I run Flows and scripts in Homey Pro to make use of low tariff hours (each hour is priced differently at my energy supplier) for running the air to water heat pump to heat the boiler. I am also waiting for a solution by Myenergi to boost Zappi charging at low tariff hours automatically. Cheers, looking forward to your reply. Ron

I'd prefer more diagrams. I found I switched off with all the numbers from the talking head!

When you’re pulling from the battery inverter, is it a sine or square wave output?

Really interesting real world example. Great video and shows the complexity of the calculation. No idea yet whether our calcs are correct - 11.6 kw system with 2 7.2 kw inverters and 2 5kwh batteries on a 3 phase supply with an ev! Plus English weather…. Too any variables…..

Really helpful information. Some time ago I watch your video where you considered installing the Puredrive battery system. I gather you didn't go for the Puredrive in the end? Can you please explain why not. I have accepted a quote to have a Puredrive battery with Solis inverter installed and I am having second thoughts. Many thanks.

Your calculations are all well and good if you are solely on an electric tariff but, if like a lot of people, you have dual energy, gas combi etc, those calculations are not so easily done. I would like to have solar, but by itself it's not cost effective without also having battery storage. One day I hope to have an EV, but their cost at present make that somewhat restrictive, however I would like to plan ahead. At the same time, cut cost presently for running appliances, and have peace of mind should the power grid fail.

You should call this channel "EV & Energy Puzzle"

You had to go for G99 application?

Hi Nigel, great work!!! Would you recomend where to get pylonthec batteries and vitron inverter? Regards

🆘I have a question to someone who can help. I am in the middle of PV installation and I run into problem because of the stubborn installer. I need to urgently buy 2 x PV panels Q-Cell G9 345W Full Black Mono. If you know someone who can help please reply.

Our experience has been that if the battery is only intended to store electricity from your solar panels there's not much point in the battery size being more than three times the rated output of the panels in kilowatt hours.. Our system has a battery capacity that's equivalent to 1.5 times the installed capacity and it often runs out of electricity in a 24-hour period . On our best days if we had 30% battery storage we could use all of the solar power we generated without sending any back to the grid,. But if the batteries were any bigger we would never make enough power to run the house and charge the batteries completely. Our house uses between 5.5 and 6.5 times the installed capacity each day in the summer which negates the longer days, so if you're somewhat overpowered with panels a bigger battery might make sense to help you through the cloudy days,. We live 32° north of the equator and I'm sure folks further north might have longer summer days but averaged over the year it's unlikely you would be able to store more power. In our case our solar system generates 5-5.5 times the installed power a day, so subtracting what the house uses from that leaves what the battery can possibly store. On the other hand if we had less than 10% of our installed power we would need help from the grid a lot more often which would make the solar panels less useful. Budget considerations sized our battery for us. Because we live in a hot climate that's also cold in the winter we tend to use 70% of our electricity during the day to run our heat pumps and the other items in the house which have not been tweaked to maximum efficiency yet. In a place like the UK you might want a large battery to store up night rate energy to use during the day and have solar there just to help you stretch out your batteries over the day. On a grander scale if every house could store 30% of its energy per day at night then, power generation could be levelized in that the plants would just make the same amount of electricity all the time and the batteries would handle the peaks.

Another great video. Esp as it focuses more on the different aspects you need to consider more than just pure math. We don’t use a lot of elec and have 2kwp solar which is still exporting a lot to the grid. Yes, an EV can consume that excess but only at above 1.4kW surplus. We’ll charge the car off peak from the grid and focus on a 5.2kW battery balancing the solar surplus and the minimisation of peak price elec from the grid. we can always add another battery and scale up as we learn, but don’t want to over purchase or oversize as all consumerism has a carbon impact. Having a smaller setup also helps you to challenge your use a little and not assume a high consumption lifestyle can be solved with lots of bling.

if looking to use the battery for peak time use - morning shower or cooking in evening - don't skimp on peak power rating of the inverter. If you can't get enough kW rate from the battery/ solar (esp. evening with oven/ microwave/ induction hob) then you'll revert to grid. G99 rated inverters will let you export the rate that the DNO dictates but allow higher power draw around your property if suitably matched.

Have you seen the v2g or v2h... I think there is a french company that has just released a ccs charger that also does v2[g/h] sounds like a better option than buying of getting too bigger battery... just use the cars one if you have access... or need a bit to take you over those cloudy days.

I've had a 4kw solar system for a few years and receive FIT payments. Can anyone tell me if installing a battery at this stage will affect my FIT payments?

Nice video, Nigel. I've been looking at the Victron Pylontech combination too. I'm starting to get my head around all the Victron models. What made you get a separate GX module? I see they make an inverter with it built in.