Posted February 2Feb 2 Hi all, with all this new BS from Eskom I am planning to bid the grid farewell soon. My installation is pretty new (Nov 2024) so far I have not switched on the grid again (although Eskom is charging me around R4500 for electricity per month). I have made it through the cloudy days pretty well with the batteries being at about 40% the following morning. When there is full sun my batteries are around 48%. My question is how will the system perform in the winter? What will I need to add to make it through? I am planning on having a standby generator just in case, but obviously don't want to use it. This is my setup currently: 16 x 545w panels, 2x 5kw Deye inverters, 3 x 5.12kw Volta stage 1 batteries. Geyser only heats during the day (but planning on moving the geyser to gas) I also have a gas stove/oven. I am located on the Northern side of Pretoria. I would greatly appreciate any advice.
February 2Feb 2 Assumptions: all the panels are facing north, with a slope at least 15° no shading of panels with trees, buildings etc daily consumption around 10 000 Wh (based on 40% of 15kW battery remaining in the morning after a cloudy day) Looks like you will be good, even during winter: https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html There will be a couple of days when your battery will run flat (below 20%), but you can bridge this with a genset easily. Just really watch your daily consumption: With the assumed 10kWh/day it's okay (as seen above). With 15kWh/day of consumption there will be 4% of days with the empty battery. And 20kWh/day is not feasible with the current system (you would need to double the amount of panels and add another 5kWh of battery at least). Good luck! Youda Edited February 2Feb 2 by Youda pics
February 2Feb 2 Through summer depending on loads in the evening like Aircon or how long the microwave works every morning my battery are are in the low 70 to 60% . In winter as the days are shorter any thing from low 50 to 60% . Batterys are charged to 100% in summer around around 9:30 am Best is never allow your battery's to discharge under 50% for battery life and rainy days . Sound like to me you need one more battery to go off grid but normally adding batterys means solar panels as well
February 2Feb 2 Author 1 hour ago, Youda said: Assumptions: all the panels are facing north, with a slope at least 15° no shading of panels with trees, buildings etc daily consumption around 10 000 Wh (based on 40% of 15kW battery remaining in the morning after a cloudy day) Looks like you will be good, even during winter: https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html There will be a couple of days when your battery will run flat (below 20%), but you can bridge this with a genset easily. Just really watch your daily consumption: With the assumed 10kWh/day it's okay (as seen above). With 15kWh/day of consumption there will be 4% of days with the empty battery. And 20kWh/day is not feasible with the current system (you would need to double the amount of panels and add another 5kWh of battery at least). Good luck! Youda Thank you for an axcellent answer! Wow!
February 2Feb 2 Author 2 minutes ago, GMAC said: Through summer depending on loads in the evening like Aircon or how long the microwave works every morning my battery are are in the low 70 to 60% . In winter as the days are shorter any thing from low 50 to 60% . Batterys are charged to 100% in summer around around 9:30 am Best is never allow your battery's to discharge under 50% for battery life and rainy days . Sound like to me you need one more battery to go off grid but normally adding batterys means solar panels as well Thanks, I am normally fully charged by 10am, think I may start with 1 extra battery and see how it goes...
February 2Feb 2 We are blessed with sunny winters. Instead of considering a gas geyser, a 150l electric geyser is around the same price. Consider that in series with your current geyser. Both can be heated to max temp during the day in sequence and should give you more than enough hot water. Your solar in the day is free energy. Gas geysers consume quite a bit and that would be an extra expense.
February 2Feb 2 As Youda suggests, do share your average daily load requirements, since feasibility hinges entirely on consumption. Try provide a busy Winter vs Summer day; and do Weekday vs Weekend. You can probably pull this from the Deye app. My anecdotal experience with the same inverter hardware as you (2 x 5kW) and a similar kWp solar array (20 x 455 = 9.1kWp, vs your 8.7kWp); situated in JHB and assuming sufficient/continuous load throughout daylight hours: Summer peaks at around 60kWh production per day Winter peaks at around 40kWh production per day Summer is far less consistent than winter due to rain (which doesn't happen much in winter); with a rainy spell dropping production by as much as 90% if it's gloomy out. In contrast, moderate clouds (where it's partly cloudy but there's still glare - and no rain on the forecast) only drops production by around 20-30%. The killer is rain clouds. Winter water heating is more power-intensive since the base water temperature is cooler and people tend to use more hot water when it's cold. This seems to be around a 30% increase in our use-case. We achieve at minimum the following targets based on the last year: Sufficient production to run essentials in daytime 99% of days (10kWh per day) Sufficient production to run essentials day and night 95% of days (20kWh per day) Sufficient production to run essentials day and night, and heat our main geyser 80% of days (30kWh per day) Sufficient production to run essentials day and night, and heat both our main and secondary geyser 65% of days (40kWh per day) A few other points related to your post: If you go gas, consider running it in parallel to electric as @zsde suggests so that you can heat your water for free when the PV is good. The last time I did the math, having to heat my water electrically for around one third of the year (like I do now) was dramatically cheaper than using gas the full year. Cooking is the same (since much of our kitchen use is when the sun is out). Also ask yourself if going off-grid electrically is going to make you reliant on the gas grid instead? If so, it might not be worth it (since an electric grid collapse would likely yield a later collapse in gas/fuel as well.) Going off-grid is a somewhat diminishing-returns exercise. At low consumption it's far, far easier, though. Provide consumption figures so we can assist! Prepaid electricity is often the most cost-effective balance between minimizing your system ROI and minimizing your reliance on the grid: we spent a week without power last year in spring and with the exception of everyone sharing the same geyser for a day or two, no-one noticed. If your electric bill is just a few hundred a month, work out how long it'd take for a generator to pay for itself. Edited February 2Feb 2 by JayMardern
February 2Feb 2 Author 24 minutes ago, JayMardern said: As Youda suggests, do share your average daily load requirements, since feasibility hinges entirely on consumption. Try provide a busy Winter vs Summer day; and do Weekday vs Weekend. You can probably pull this from the Deye app. My anecdotal experience with the same inverter hardware as you (2 x 5kW) and a similar kWp solar array (20 x 455 = 9.1kWp, vs your 8.7kWp); situated in JHB and assuming sufficient/continuous load throughout daylight hours: Summer peaks at around 60kWh production per day Winter peaks at around 40kWh production per day Summer is far less consistent than winter due to rain (which doesn't happen much in winter); with a rainy spell dropping production by as much as 90% if it's gloomy out. In contrast, moderate clouds (where it's partly cloudy but there's still glare - and no rain on the forecast) only drops production by around 20-30%. The killer is rain clouds. Winter water heating is more power-intensive since the base water temperature is cooler and people tend to use more hot water when it's cold. This seems to be around a 30% increase in our use-case. We achieve at minimum the following targets based on the last year: Sufficient production to run essentials in daytime 99% of days (10kWh per day) Sufficient production to run essentials day and night 95% of days (20kWh per day) Sufficient production to run essentials day and night, and heat our main geyser 80% of days (30kWh per day) Sufficient production to run essentials day and night, and heat both our main and secondary geyser 65% of days (40kWh per day) A few other points related to your post: If you go gas, consider running it in parallel to electric as @zsde suggests so that you can heat your water for free when the PV is good. The last time I did the math, having to heat my water electrically for around one third of the year (like I do now) was dramatically cheaper than using gas the full year. Cooking is the same (since much of our kitchen use is when the sun is out). Also ask yourself if going off-grid electrically is going to make you reliant on the gas grid instead? If so, it might not be worth it (since an electric grid collapse would likely yield a later collapse in gas/fuel as well.) Going off-grid is a somewhat diminishing-returns exercise. At low consumption it's far, far easier, though. Provide consumption figures so we can assist! Prepaid electricity is often the most cost-effective balance between minimizing your system ROI and minimizing your reliance on the grid: we spent a week without power last year in spring and with the exception of everyone sharing the same geyser for a day or two, no-one noticed. If your electric bill is just a few hundred a month, work out how long it'd take for a generator to pay for itself. Thank you Jay for the valuable input. I agree that the dual geyser heating system might be the way to go. My consumption is around 900kw per month (although it goes up quite a bit running the AC when the power is free). Having seen some people who have 'leagalised'their solar systems having to pay between 20 and 50k I would rather take that money and invest it in a generator. Then you have to pay the " energy availability fee" per month... then we never know what stupid law they will think up next. All in all, I just think it's better to get rid of eskom entirely. Our local municipality has overcharged me for electricity by about R4500 per month so far, so I think for my sanity I just want to get away from eskom. Is my thinking flawed? I am pretty pissed
February 2Feb 2 1 hour ago, johnna said: My consumption is around 900kw per month (although it goes up quite a bit running the AC when the power is free). Are you sure? That would be 30kWh/day. Not only that's a lot, but your current system should not be able to provide so much during those cloudy days. Can you double-check the numbers for different days, as @JayMardern suggested, please?
February 2Feb 2 Author I am pretty new to this stuff, so I may be totally wrong🤣. Here is the report for the year so far
February 2Feb 2 Oh my, that's really 25-30kWh every day! What are you doing with all that electricity? Mining Bitcoin? Charging EV? Or is it the Air Condition maybe? If that's A/C, then your consumption should go down in the winter, I suppose. Anyway, I would suggest to try being disconnected from the grid for as long as possible, and get some consumption stats for the 1st year. Then you can decide what to upgrade, if anything. Just remember - speaking of solar, the only thing that generates electricity are the panels. So there's no point in increasing capacity of batteries if you lack PV generation each and every day for a week or two. Batteries will help you bridge a day or two, but not a week or month. Edited February 2Feb 2 by Youda wording
February 3Feb 3 I have similar specs, just above 20kWh batteries and using as much PV as available with gas as topup on geyser. By adding another battery you should be able to be 98% offgrid but need to manage pool, geysers etc to ensure PV is available.
February 3Feb 3 If you don't have power-hungry heaters the winter PV (is normally more consistent day to day) should be able to cover your daily consumption... As above you'll most likely best off with electric and gas geyser in series. I also have borehole and pressure pump on my load and can run dishwasher twice during evening if required.
February 4Feb 4 I live in Hillcrest which is about 25 km inland from Durban and its 2200 ft above sea level.We get tons of mist and drizzle in summer so sometimes I scratch but its workable. Yes winter days are shorter and sun is weaker BUT we have guaranteed sun so my output in winter is often more than summer. I have 1x 8kw sunsynk, 3 x hubble am2 and 7.25 kw of panels. I have a geyserwise system and with management in summer I "give" ethekweni about R120 pm of electricity just to keep them quiet. On hot days i use my lounge aircon off the panels without blinking and in winter use the ac to heat the lounge if i am too lazy to make a fire. Interesting how everyone has a different story/ need on solar. Edited February 4Feb 4 by Nicholas Strachan
February 10Feb 10 Wow... So I have been monitoring my consumption daily recently. And my consumption is going up a lot. I use between 18-26 KW pd. We are a family off 5 (I think the air cons are the culprit here). We only have a 5kva and 6 panels. My electricity costs about 2500 pm. How do you guys manage that? If I add another 5kva - I think that would help with lightening some of the load in the eve... But would that really save me considering my air cons and geyser as they're solar (which I don't switch on in summer) are connected to eskom
February 10Feb 10 On 2025/02/02 at 1:16 PM, johnna said: 16 x 545w panels, 2x 5kw Deye inverters Thats what you stated in your original post. 51 minutes ago, jamila said: We only have a 5kva and 6 panels. Now you state this Can you clarify please.
February 10Feb 10 Author 19 minutes ago, zsde said: Thats what you stated in your original post. Now you state this Can you clarify please. It was not me who made the second statement 👍 it was Jamila
February 10Feb 10 [edited out by dozy @Bobster. Edited February 10Feb 10 by Bobster. Redundant comment
February 10Feb 10 As this is an ongoing Eskom process.Switch off the Eskom mains from today to ascertain if what you have is enough to sustain your household and apply this across a few months.Try not to be too conscious of saving electricity because you want to get thru the days but rather live normally until Spring and you will get a reasonable idea of what you require to get off the grid. I applied this process from April- November 2024 and now i am busy plugging all the gaps and pitfalls so that i can move off the grid next year. Note that you will get the estimated billing from your grid supplier for sometime until they correct it. Another suggestion is to consider using the option of a heat pump instead of the geyser or reliance on gas for any heating as that adds up to your gas cost.The heat pump uses a quarter of energy to heat up the same amount of water when compared to a geyser.Your geyser simply becomes a storage facility for the heat pump. if you have a pool,covering the pool allows your pool pump to run less in a day.I actually got away with 2 hours a day in Winter and 4 hours a day in Summer.My pool was sparkling clean despite being around trees. With this experiment,you will be able to have a reliable data specific to your household to work with so you can safely go off the grid.
February 10Feb 10 2 hours ago, jamila said: We only have a 5kva and 6 panels. My electricity costs about 2500 pm. How do you guys manage that? OK... what would your bill be if you didn't have those panels and battery? That's how much you're saving. I am not going to ask, but look at what you paid, look at the ROI you're getting, and remind yourself you have some backup when the grid goes down. Now you can decide if it's a good deal for you or not (the answer is different for each of us). You're five people. It's harder for you to optimise than it is in my situation, with two adults fairly well set in our ways. 2 hours ago, jamila said: If I add another 5kva - I think that would help with lightening some of the load in the eve... But would that really save me considering my air cons and geyser as they're solar (which I don't switch on in summer) are connected to eskom The simple answer is you have to do as much electrical work as possible whilst the sun is up. As I said above, the more people you have in the household and the more varied their routines, the more difficult this is. I shower pretty much the same time every day, so does the wife. And besides I don't heat water when the sun has gone down (other than to make coffee). NB! We also have full gas cooking. I think two things happen 1) Any half way decent system is going to make available lots of data about usage in the house, but either people don't know or don't look. So look. This will help you identify when you are using electricity and, as you look & learn more, on what. Then you will see where you can cut back or "move" loads into the daylit hours. 2) People just get a system installed in some default mode and don't understand the options available to them. This is another reason they don't get the most out of their systems. EG my system has TWO settings related to how much battery it will allow to be used. One for when the grid is up, and one for when it's down. So this means I can know that I will always have a certain amount of power available when the grid goes down - and I set that at the point I'm comfortable with. Edited February 10Feb 10 by Bobster.
February 10Feb 10 Just now, Bobster. said: 1) Any half way decent system is going to make available lots of data about usage in the house, but either people don't know or don't look. So look. This will help you identify when you are using electricity and, as you look & learn more, on what. Then you will see where you can cut back. 2) People just get a system installed in some default mode and don't understand the options available to them. This is another reason they don't get the most out of their systems. EG my system has TWO settings related to how much battery it will allow to be used. One for when the grid is up, and one for when it's down. So this means I can know that I will always have a certain amount of power available when the grid goes down - and I set that at the point I'm comfortable with. Also, in some households, people confuse "solar" with "unlimited free electricity". Which, as you're finding out, it isn't.
February 10Feb 10 Hi @jamila 3 hours ago, jamila said: Wow... So I have been monitoring my consumption daily recently. And my consumption is going up a lot. I use between 18-26 KW pd. We are a family off 5 (I think the air cons are the culprit here). We only have a 5kva and 6 panels. My electricity costs about 2500 pm. How do you guys manage that? If I add another 5kva - I think that would help with lightening some of the load in the eve... But would that really save me considering my air cons and geyser as they're solar (which I don't switch on in summer) are connected to eskom To be honest, 6 panels for a family of five is almost nothing. Assuming cca 500Wp per panel, that would be just 3kWp, which translates to roughly 15kWh per day in SA. Not so bad on a first sight, but there's a lot of gotchas: If the system is connected to the grid, and you start any load higher than 2,5kW and it's not perfect noon, then you will be drawing that missing power from the grid (or batteries.) On a cloudy/rainy day the power drops quickly. Next day, you have to satisfy the loads, but to charge the flat battery at the same time. If your house wiring is 3-phase, but the PV system is 1-phase, then the benefit is minimal. Etc. If you are not electrician, installer or PV geek, then I would advise you to get in touch with a reputable PV installer (or company) in your area, have them check your current PV system, loads, house wiring, family needs and then design a detailed plan of PV system upgrade based on the calculations. If you want a quick answer, then from my experience the reasonable solar for a family house starts at 10kWp of PV (cca 20 panels), 20kWh of lithium battery, 10kW of inverter power. For offgrid use, 1-phase wiring and inverter makes sense most of the time. But like I said - check your situation with an installer. 1 hour ago, Bobster. said: 2) People just get a system installed in some default mode and don't understand the options available to them. This is another reason they don't get the most out of their systems. Not to mention that I've seen 1-phase solar in a 3-phase house. Or a PV system, that was configured as backup only, not helping the house loads at all. Edited February 10Feb 10 by Youda
February 10Feb 10 4 hours ago, johnna said: It was not me who made the second statement 👍 it was Jamila @Energy-Jason any possibility of splitting this thread so that @jamila has their own @johnna My apologies, not quite sure why your thread gets hijacked,
February 10Feb 10 Author 38 minutes ago, zsde said: @Energy-Jason any possibility of splitting this thread so that @jamila has their own @johnna My apologies, not quite sure why your thread gets hijacked, No problem, thank you🙏
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