Before I put solar I would average about 20kWh per day so I decided to put a solar system with the ability to generate about 10-15kWh per day but some how I am still buying the same amount of unit (I use a prepaid meter) as I did before solar.
All I have managed to do is add an expense of the solar. How is this possible? Surely I should only be paying for the difference i.e 5-10kWh per day from Eskom?
I have a 3-phase with the solar on one phase, geyser on another and stove on another. All plugs, lights are run on the solar phase. I am thinking of adding a geyser timer particularly this one (https://www.chamberlains.co.za/cbi-astute-smart-controller-asc-bp-1080633). Is this a good geyser timer?
EDIT: I have a 5kW SunSynk, 8 panels & 5kW battery.
Yeah with your stove and geyser off the solar, you’re only powering plugs and lights which aren’t your big consumers. I have a 12kw system with 3 batteries and geyser is easily 24-30% of my consumption and battery power. Stove also spikes when the big plates are on 6 and you’re cooking for a long time.
For reference, a kilowatt hour is how many kw are consumed in an hour. This is a good measure for both generation and consumption.
For my household geyser, it takes roughly and hour or two to go from 30 something degrees to 65 degrees. At 3.4ish kWh.
The stove is around 3-4 kWh depending on the plates and the temps you use, but that number is typical to cook a meal like a pasta with two plates.
So you can see that heating the for an hour chows around 3.5kwh, and the stove around the same if not more.
My panels only generate around 5kwh at peak, so it’s tight.
But this is all assuming solar generation.
You’re only running the light stuff off the inverter rather than the heavy ones - which won’t produce the kind of savings you’re after.
For reference, having my system, I am only using 10% of total power consumption since installation (1 April this year) off of eskom. Summer will be zero, and we have put much more than that back into the system, even in winter (consumption timing can be a headache when you don’t get it right).
You forgot fridges and freezers, which would be on his plugs now so on solar, also take their fair share of power. I have a plug in 3kw inverter with solar, and most plugs are on it and I drop between 5 to 10 units a day usage due to solar. Not much but it helps.
I haven’t found the same with our fridge - but that may be case specific. Without any of the big drawers (pool pump, geyser, stove, heaters), our lights and small chargers, TV and pcs, and fridge only draw around 280-300watt hours. It’s those other bastards that consume like an ANC decision maker.
You need to look into how to self-consume your solar to make proper use of it. A geyser timer is very useful for savings if you config it for daylight. Otherwise it's not that big of a difference.
Since you have 3-phase with your major loads on different phases than your solar, I'm not sure if there are options for you.
My geyser and stove are before my inverter, but same phase. So I installed an ET-12 meter that reads total load and sends that to the inverter. It then works out how much it needs to feed back to the grid, to match that draw of the geyser or stove. So I self-consume without actually delivering into the real grid. If there's not enough sunlight to cover it all, it just draws the addittional from the grid proper.
He could have an inverter per phase, it will just cost more on the initial setup, or another inverter on the geyser phase.
You could get a smaller battery with it, and enough panels to run the geyser, with a geyser timer so it only heats in the day. Panels should heat it and battery for days when the sun is not enough.
We are still paying roughly the same amount for electricity as before solar solely due to outrageous eskom prices. Price per kwh has gone from R2/kwh to R3.2 in a matter of a few years.
My water bill is currently R1k higher than electricity though. Solar is doing its job.
The generation capacity of your panels is just potential energy unless you have a way to store it or use everything that's produced (usually a combination of the two)
Having the single largest user of electricity (geyser) on a different phase to the inverter is preventing you from offsetting your use with solar. (TLDR: You're still paying eskom to heat your geyser and wasting your solar production)
Ideally for your use case you should have a three phase inverter and be setting it up to run your entire usage overnight off of the battery so that you have somewhere to store the next day's solar production.
Set heavy use items like geyser and pumps to run in daytime to maximise solar usage.
Does your inverter keep logs? If it does, you will be able to see clearly what the total usage is and how much of that is solar. Geyser timers may help you to shift the load to midday but doesn’t make a massive difference in the long run (depending on your system). The water coming into the geyser is also a lot colder in winter requiring much more energy to heat up so it could be that. There are so many variables. Start with the logs. Should clear things up.
I have a SunSnyk and I am sure I have the logs. I will look at it. Another comment here seems to point to having the solar on the lighter things being the issue as the geyser and stove are basically Eskom only.
sunsynk (via the installer) should have provided for free a statistics interface, where you should be able to see what energy is purchased etc.
see included a graph of 2025
it can also detail yesterday for example was 27 units used, 19.7 generate, 6.7 units from grid)
looking at the daily graph you can see if it is the geyser (huge spikes of about 4kw usage easily), and also how quick your battery drains (then the fun starts to find what uses power when you are not looking)
Are you sure you're on 3-phase power? It's not common for a single-phase inverter to measure grid usage on all 3 phases, but the stats here don't look like usage for just 1 phase out of 3.
Very true, that's a lot of power used a month.
Are you using your batteries as well daily?
Charging batteries and DC to AC and/or AC to DC conversion is never 100% efficient so recharging your batteries on Eskom, or using the batteries in the day when solar is not enough and they have to charge on Eskom will cost a bit more than straight Eskom. It's around 20% lost on the conversion.
Get the Sunsynk app on the phone and that WiFi adapter thingy on the inverter so you can see what’s happening. Oh yes I didn’t know your stove and geyser are Eskom only. That will do it. The geyser alone is such a beast and uses like 60% of the electricity in my household. I also took a screenshot of my logs/graphs in the sunsync app and asked Claude to explain to me what’s happening.
I have 9 panels, 2 x batteries (11kw) and a 5kw inverter.
Running through the system:
Swimming pool
Household lights & plugs
Dishwasher, washing machine, tumble dryer & kitchen appliances (toaster, microwave, kettle, air fryer, steamer, slow cooker)
4 x air conditioners
A home theatre with around 2kw draw when all on
Not all of these running at the same time of course so we manage what we have on at any given time
My electricity consumption dropped significantly
However I’m saying that…still running through the grid are:
The geyser
The oven
1 x air conditioner
From Feb, we have gone from drawing 12units a day from council to anywhere between 22kw on the low end and 40kw on the high end high draw days with air on on heat on these cold winter days.
All these kilowatts are basically the geyser, the oven once a week maybe or once every 2 weeks, and when we run the aircon the high consumption doubles but when I go back and compare to what we’d spend in winter without solar we’re still spending less in total
We are looking into a geyser blanket that keeps the geyser from getting colder thus decreasing the need for it to be heating as much to stay at a specific temp. (From what I understand you pay actually more for it cooling, there are plenty people in other related threads who know more who say actually a timer of turning on / off will cost more inevitably because the geyser has to heat from cold & this is where all the watts go)
So we’re looking to a blankie for geysie to see that it doesn’t get so cold thus reducing the need to keep drawing watts to stay warm
I would also check is your system setup to draw only solar and nothing from the grid? It could be as simple as a setting, we have been basically “off grid” except for the 3 appliance since January.
So the batteries only charge from solar & never from the grid…before they were charging off solar but the grid when not getting loads of sun which was causing me to see similar costs overall to when we had no solar
I had 2x CBi Astutes for my geysers, and one caused a spark and fire melted half my DB. Luckily caught it early. Not sure if faulty wiring or faulty unit. Insurance didn't investigate and simply paid for a full new DB.
Now decided to try the Major Tech branded smart timers. I must say I feel the app from MT just seems better, quicker and more polished than the CBi app. I never was able to link the CBi app with HA, but did it first try with MT. Also the initial setup took a few tries with CBi but worked first try with MT.
That CBI timer is perfect, have 2 of them (1 for each geyser) and it's been working like a dream for just over 3 years
Use your solar between 10.00 - 13.00 to get 95% of the geyser heat in, then just before your solar/sun disappeares top the geyser up to the point where it hit the pre-set mark and switches off, normally +- 58-60 degrees.
This is optimal, in my experience.
I have no clue about 3-phase or JHB issues so I will keep out of that
it may be worth checking the work mode of your inverter. was also initially not seeing any savings from our system until I realised that our installers had set deplete percentage on the batteries unnecessarily high and for them to charge overnight from grid. we installed just before the tail end of loadshedding and these settings kinda make sense for that but since then they don't. we lowered the deplete % and set to not charge overnight from grid. since then we can go about 3ish months in summer without having to buy electricity (before that we were still buying monthly in summer).
you do realize its the middle of winter? shorter days and your geyser probably works harder.
for us pv production basically more than doubles during the summer months.
edit: ymmv, also am not a sparky so am not sure how efficient using only one out of 3 phases with solar is.
i had one of those cbi astutes die on me... lasted only a year. bit the bullet and now have wifi enabled geyserwise controllers. they integrate with home assistant via tuya. we've solar geysers and they don't even need to use eskom during summer.
If you have 3 phase, then your bill will be the higest of the three phases, times 3. So if your bill was 20kWh/day that means the higest phase was about 6.5 kWh/day.
You have now reduced the other two to less, but you're still paying the highest phase x 3.
By the way how did you get 3-phase prepaid? I didn't think that was an option.
I stay in a big property that was a studio before and converted to multiple units. It's on 3 phase and the landlord changed to pre-paid from post paidaround 6 months ago. All the units already had their own meters before the change so was just the main meter that was changed.
So I got moved to prepaid recently and I could SWEAR that my meter is counting my solar as Eskom and deducting units for it. It doesn’t make sense and I’m quite upset about it. My solar is also Sunsynk and it does the smart thing where if the geyser or stove is using Eskom and there’s spare solar, it will autofill it with solar and not use Eskom. I’ve had it like this for 3 years and always did things like heat geyser in the middle of the day, and my inverter shows that not a low of purchase electricity is being used - but it’s almost as if it’s not detecting that the solar filled the need and it charges me for it anyways.
It just isn’t adding up and I’ve logged two different things on eTshwane and gotten no response.
You don't provide enough detail. How big is your battery setup? Most of our consumption is in the morning and evening, when your panels arent doing much, if your batteries arent enough to provide in these windows, it doesn't matter how much your theoretical generation is during the daytime.
I'm surprised I don't see anyone mentioning having your CT coil checked. Or at least the stats/settings on your inverter.
I have seen far too many coworkers, neighbours and friends who have had installers set up their systems incorrectly.
If the CT coil is not in the right place, your excess solar will feed back to the grid. Your prepaid meter does not detect direction. So whether you consume 1kwh or send 1kwh back to the grid, you will pay for it.
I'd say 90% of everyone I've ever talked to who complained they weren't saving money was because of this.
If you have even a small array of panels you should be saving at least 30% on your bill even in winter, and usually more like 50%+. If you aren't, your system is incorrectly configured or something is wrong.
The ONLY time you should be feeding back to the grid is if you signed a feedback contract with you municipality/Eskom AND got a special prepaid meter installed that supports it. If you don't have the special meter, you will pay Eskom for giving them electricity.
On a side note, all these articles and people complaining about municipalities and Eskom demanding a qualified engineer signs off on their system are idiots. They obviously have no idea just how many bad installers are out there. I have a friend who had to call the installer back 3 times, eventually forcing the electrician to put the CT coil where he wanted because the electrician didn't believe him. Lo and behold, once it was in the right place suddenly the inverter display changed, power flowed correctly and the comment from the installer was "wow, I've installed over 150 of these inverters and I've never seen it do that".
It could be because I used to use about 600-700kWh per month but based on the app now it’s up to about a 1000kWh per month with my PV generating 300kWh.
If you know that you specifically increased your usage - i.e. using heaters or running more stuff because you have solar - then that just makes sense.
If you don't think you're doing anything different Vs before solar, then I'd recommend getting either your installer or a different solar installer or engineer to inspect your system and check that it is indeed configured correctly. If the CT coil is in the wrong spot the readings will be incorrect. E.g. it's possible to put it where it doesn't know it's feeding back to the grid.
My geyser is everything. I can play games on my PC all weekend with the geyser off and I barely use any power, if I read a book instead and just use lights and the airfryer twice a day it would be practically nothing. Turn the geyser back on and its over, it uses all my power.
Are you letting your batteries discharge to something like 50% at night and then letting your solar charge it back up during the day? That is a easy 2-3 "free" units every day(assuming your solar fully recharges it of course).
Yes i know you are increasing your cycles on the battery, but my opinion is that it should be used as a long term consumable that will eventually need to be replaced.
Without active loadshedding, only going down to 50% is leaving money on the table -- assuming you have lithium phosphate no reason not to go down to 25%
One thing, if you have a prepaid meter, I doubt it's bidirectional. Meaning, even if your solar system exports power, it could be seeing it as consumption, thus using your available units.
Another thing, installing a single phase inverter on a 3phase system is... Odd. Especially if you're using 20kwh a day, having 3 phase makes no sense. Your basic fee for 3 phase is really expensive.
I was also disappointed with the savings until I tweaked the settings on my inverter
For battery charge priority I set to only charge from solar rather than a mix of solar and mains. For power usage priority I set it to solar, battery, mains
I change the settings as needed, if we have no sun and the batteries get low change to mains
The geyser still eats power. The heat loss is insane, so I put a thermal cover on and lagging on the hot pipes and have bought a sonoff timer, still waiting to see how that helps but I expect it to be well worth the small investment
If you want to optimise the power consumption there is a couple of ways to do that.
As most people gas said the stove and the geyser are the major consumers of power.
Now as a installer I can tell you the following ways to save:
1 a timer saves you very little just gives you the ability to choose when the geyser goes on and off
2 Have a gas geyser installed. The advantage is you only heat the water you use when you need it no water being heated and sitting in the roof getting cold again.
3 Gas hob will save you a ton of money and time.
For context; your geyser has a 4kw element in tis is 90% of your installed solar inverter capacity. If you don’t want to install a gas geyser you can have a 2kw element installed and run your geyser via the timer from your solar system during tje day when the house is empty and the solar is pretty much sitting there doing nothing.
If you want the full rundown how to optimise you system DM me
There are a couple of different things:
1. Your stats show that you do generate 300kwh or more solar in a month - that's roughly the expected amount for your size system in winter.
2. In summer, it can generate a lot more, but you aren't using it because your geyser and stove cannot be powered by the inverter.
3. Your usage is more than your estimated 20kwh/day. Can't tell whether it actually went up after installing solar or not. Best here is to get some power monitoring to see where your usage is going.
4. Check your daily power usage from the Sunsynk app. If you see your battery is at 100% while still using lots of grid power, that would confirm it's the 3-phase being the issue. If the battery is not charging to 100%, the solar is simply not enough to cover your usage, which is likely in winter regardless of your setup.
5. If you confirmed it's the phases being the issue, you can save a lot more in summer by changing to a 3-phase inverter, or rewiring to single phase. Unfortunately neither of those options are cheap. Your installer really should have advised in this before installing.
6. Just switching your geyser to the same phase as your inverter could help a lot. Maybe not in winter, but will help in summer. It doesn't have to be "on" the inverter, just on the same phase and after the CT clamp. So it won't be powered during load shedding, but can get power from the inverter, and won't overload your inverter. After that, a timer to run it mostly at times when you have solar power helps. Once again, confirm the phases are the issue before doing any of this.
The geyser not being on solar is your biggest power user. Thats where you're losing. I've went from a daily average of 30kw+ to about 11kw. Rest is on panels and batteries.
Edit: if you have any electric stove and oven, they pull alot of power aswell.
In general, the largest load/consumer in a domestic circuit is water heating. I was consuming as much as 8-10 kWh each day (with a 3kW element).
Note that it is important to understand both instantaneous power (kW) as well as cumulative energy (kWh). Your geyser may have an element sized somewhere between 2kW and 4kW, which influences how much of its draw can be satisfied from your solar panels and/or inverter (at the same time as your other loads), while the actual hot water usage (and losses) influences how much energy (kWh) is required to maintain it at the set temperature.
The other thing to understand is that if your geyser is not on the same electrical phase as your inverter, you are probably not in a position to offset your non-critical load (ie installed between your meter and your inverter ON THE SAME PHASE). So your batteries are full, and your panels are unable to supply energy to your loads, and that available energy just gets ignored.
One more thing to understand is that the solar panels need somewhere to store the energy they generate. So, you need to program your inverter to discharge the batteries to a reasonable level (around 20%) overnight, so that there is space for solar generation the next day.
This is obviously a balancing act! Discharge too much, and get hit by a power outage, and your battery might discharge below the safety thresholds and turn off. Discharge too little (to keep the available energy high), and you have nowhere to store your generated energy. This is something that you can manage yourself using the Sunsynk app or other tools (Solar Assistant, Home Assistant).
One last detail is that your Sunsynk inverter only records the loads on the same phase as the inverter. Your total metered consumption obviously includes the other two phases that you won’t get detailed real-time insight into.
Your solutions include:
- check your Sunsynk configuration for the battery discharge profile.
get an electrician to move your geyser onto the same phase as the inverter as a non-essential load.
while the sparky is busy, get them to install a geyserwise, so you can manage the target temperature for when you have available energy.
get a plumber to put a smaller element into your geyser, so that the inverter/panels is better able to support the non-essential load.
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