CliveSA

As the inverter is attached to the buildings it should be covered under buildings insurance - and the rates will be a lot lower. All risks is effectively meant for items you can carry around - and get stolen (lost) easily. A rule of thumb, if you turn your house upside down does the risk stay behind. For an inverter the answer is yes so it is covered under buildings insurance.

The insurance  industry is "struggling" with inverters and their risks - it is only very recently that lots of people have installed inverters. Policy wordings (and procedures) ae not always up to speed. Most insurers are now insisting on a CoC.

I would make sure that you keep the communication with your insurer - in case their are any issues at claim stage. I would keep a record of:
The invoice The exact items installed; The CoC that was provided. With load shedding and the rise in claims many insurers have removed cover for power surge - or limit cover. It poses a risk to you as an inverter system could easily be worth R100k+. Whilst the risk of a power surge is really limited, it could be a financial mess if your system is wiped out by a power surge and your cover is limited to R10k. Be very careful here.
Some insurers have also required surge protection (arrestors)  - and this protection to be checked regularly - for their to be cover. Surge protectors are usually installed with an inverter - don't think many people think of maintaining them.

As the inverter is attached to the buildings it should be covered under buildings insurance - and the rates will be a lot lower. All risks is effectively meant for items you can carry around - and get stolen (lost) easily. A rule of thumb, if you turn your house upside down does the risk stay behind. For an inverter the answer is yes so it is covered under buildings insurance.

The insurance  industry is "struggling" with inverters and their risks - it is only very recently that lots of people have installed inverters. Policy wordings (and procedures) ae not always up to speed. Most insurers are now insisting on a CoC.

I would make sure that you keep the communication with your insurer - in case their are any issues at claim stage. I would keep a record of:
The invoice The exact items installed; The CoC that was provided. With load shedding and the rise in claims many insurers have removed cover for power surge - or limit cover. It poses a risk to you as an inverter system could easily be worth R100k+. Whilst the risk of a power surge is really limited, it could be a financial mess if your system is wiped out by a power surge and your cover is limited to R10k. Be very careful here.
Some insurers have also required surge protection (arrestors)  - and this protection to be checked regularly - for their to be cover. Surge protectors are usually installed with an inverter - don't think many people think of maintaining them.

Hi @Scorp007,
Very valid calculation - and don't disagree. A bit of an overly blunt (generalized) statement from my side.
My argument was based on:
There is currently PV installed - likely producing excess electricity There is a geyser installed - changes which heat pump to buy. A heat pump will probably cost R17k today - there is no Eskom rebate and there are also installation costs. The excess electricity from the PV, assuming there is some excess, costs R0. The batteries will have a useable capacity of about 9kwh. The average solar production maybe sits somewhere around 18kwh. Some of that will be solar production will support the daytime usage but I suspect - on a normal day - there is a lot of excess solar that is going to waste.
If I look at a family of 4, mainly showering, you should average 240kwh for the geyser in a month - 8kwh per day. At current electricity prices (JHB, prepaid, worst block) of  R2.54/kwh, it will cost R7.3k over a year. But if majority of the electricity comes from PV then the savings reduce significantly - could be 30% (or less) of the figure.  With a solar system I would expect most houses should fall into a lower tariff block. The heat pump should theoretically cost nothing to run as the excess solar should cover the heat pump electricity usage - but the timing of the heat pump could create some 
Biggest differences between my (and your calculations):
I worked on my average hot water usage which is lower - about 50%. How much electricity is sourced from PV vs Eskom - impacting the unit cost. What is the return you need, what are your usage patterns, are you going to stay in the house for 12 years, what will Eskom prices do, ... so many assumptions.

I guess we all have to be comfortable with the decisions we make, knowing the you will be wrong - just how wrong.

Don't know the Deye inverter very well but I believe you have a non-essential load. The Sunsynk has this functionality. Your stove & geyser should be on the non-essential load - so when you use the devices they make use of the excess solar.
As a first step I would place the geyser on a timer switch. Run the geyser at about 1/2pm. This should mean you get an immediate saving - but some of the power may be drawn from the grid. Using a 2kw element will double the time your geyser runs for - but then most of the power will be pulled from solar. With 4.5kwp, a 4kw geyser will exceed what can be provided by PV - along with the load for the rest of the house.
If you don't use a huge of hot water you won't see the impact of a 2kw element. The reality is that the geyser only runs for brief periods of time. For example:
You use 100l of (pure) hot water in a day, The incoming water temperature is 15C You heat your water to 65C. You need approximately 6kwh to heat the water, heat losses (for modern) geysers is minimal.  A 2kw element means your geyser needs to run for 3h whilst a 4kw geyser would only need 1.5h.
You can increase savings by heating your water up - to say 70C. It will avoid running the geyser at night. Maybe have a look at the GeyserWise smart system - that works with Wifi to optimise your geyser.
A heat pump will save more electricity but the ROI doesn't make sense to replace your geyser.
I am doubtful on claims on more efficient geyser elements - any waste will be converted to heat which will be released into the geyser anyway.

Almost certainly overkill but Revov has designed a ‘cube’ that could work, it comes with a lot of the necessary wiring and circuit protection built in.
https://revov.co.za/wp-content/uploads/2022/12/9-REVOV-CUBE_SpecV2-Refresh.pdf

I would save up and get an Efergy (or other brand) monitor. They use a (CT) clamp that goes around the input wire on your DB board - so no cutting. It's a lot easier than installing a smart DB switch. Data gets uploaded to the cloud so you can monitor your peak usage and when you use electricity. It does monitor total demand but you get an idea of which devices (circuits) are using electricity quickly - and can focus on finding inefficient devices. Check your draw, switch on a device, wait 30s and then check the app again.
From experience, it's a very good way to save electricity quickly. You can comfortably say goodbye to tumble dryers, halogen lamps, large pool pumps,3 geysers, etc.
It will also be really helpful to help size your solar system as you have a far better idea of your power usage. Batteries are expensive and to get the most ROI you will want to maximize your power usage during the day.

IF you need to you can take it a step further. A kill-a-watt meter can also help to look at specific devices that operate off a plug. You can also make a power monitoring device using a Sonoff/Shelly/Tuya smart switch. Many of them have power consumption meters and will give more detailed data than a kill-a-wat - just a bit of DIY. I would use a Sonoff IP66 box and you can make a mini extension lead to see the demand profile over a period. Make sure you keep your load (well) below the rated maximum. 

I would save up and get an Efergy (or other brand) monitor. They use a (CT) clamp that goes around the input wire on your DB board - so no cutting. It's a lot easier than installing a smart DB switch. Data gets uploaded to the cloud so you can monitor your peak usage and when you use electricity. It does monitor total demand but you get an idea of which devices (circuits) are using electricity quickly - and can focus on finding inefficient devices. Check your draw, switch on a device, wait 30s and then check the app again.
From experience, it's a very good way to save electricity quickly. You can comfortably say goodbye to tumble dryers, halogen lamps, large pool pumps,3 geysers, etc.
It will also be really helpful to help size your solar system as you have a far better idea of your power usage. Batteries are expensive and to get the most ROI you will want to maximize your power usage during the day.

IF you need to you can take it a step further. A kill-a-watt meter can also help to look at specific devices that operate off a plug. You can also make a power monitoring device using a Sonoff/Shelly/Tuya smart switch. Many of them have power consumption meters and will give more detailed data than a kill-a-wat - just a bit of DIY. I would use a Sonoff IP66 box and you can make a mini extension lead to see the demand profile over a period. Make sure you keep your load (well) below the rated maximum. 

I would save up and get an Efergy (or other brand) monitor. They use a (CT) clamp that goes around the input wire on your DB board - so no cutting. It's a lot easier than installing a smart DB switch. Data gets uploaded to the cloud so you can monitor your peak usage and when you use electricity. It does monitor total demand but you get an idea of which devices (circuits) are using electricity quickly - and can focus on finding inefficient devices. Check your draw, switch on a device, wait 30s and then check the app again.
From experience, it's a very good way to save electricity quickly. You can comfortably say goodbye to tumble dryers, halogen lamps, large pool pumps,3 geysers, etc.
It will also be really helpful to help size your solar system as you have a far better idea of your power usage. Batteries are expensive and to get the most ROI you will want to maximize your power usage during the day.

IF you need to you can take it a step further. A kill-a-watt meter can also help to look at specific devices that operate off a plug. You can also make a power monitoring device using a Sonoff/Shelly/Tuya smart switch. Many of them have power consumption meters and will give more detailed data than a kill-a-wat - just a bit of DIY. I would use a Sonoff IP66 box and you can make a mini extension lead to see the demand profile over a period. Make sure you keep your load (well) below the rated maximum. 

Not 100% ideal from a safety perspective if something goes wrong with the lithium battery. I know that some electricians have refused to sign-off a CoC if the battery is installed indoors. However, this is the arrangement I and my parents have - two independent parties were OK with a battery indoors in a room. Mine has been running for a couple years with no issues.
From a safety perspective I would argue that a fully compliant inverter, with a lithium battery, is probably the safest option - a lot better than extension cords, batteries, SLA batteries, et al.
I have this setup and load shedding is (basically) a non-event. I don't connect my stove, geyser & dishwasher. Everything else runs off the battery. Other household members have shown that it works well with hairdryers & and irons. We have had no power for about 12 hours and comfortably remained working from home, having tea, lunch & dinner. The batteries dropped to 20% on that occasion.
I can cook with the microwave oven function. Only once had a warning light when using the microwave oven & an induction plate at the same time - for a while.
You don't need to worry about the geyser as water will remain hot for 4 hours. Connecting the stove will be problematic as you could easily forget and overload the inverter - and battery.
The advantage of going complete overkill is that it will be very difficult for something to trip or go wrong - and the resulting panic that it could cause. A hairdryer and kettle being used at the same time. An inverter with a passthrough function will also help - as it reduces the likelihood of tripping further. You really want something that is simple and can be left alone. I wouldn't bother too much with remote monitoring - you won't be able to do much. Trying to troubleshoot over the phone will be difficult.
You will need to check this. Some inverters need a lot of clearance which can be difficult in a smaller room. My Victron clearance limits meant this was fine - a story for another day on why that inverter, it was a long time ago. But is does occupy a fair section of the wall - as it had to be positioned away from the wall.
I close the bedroom door if there is load shedding. That switch from inverter to grid can be heard. You also hear the inverter when the batteries are charged - but that lasts a couple minutes. You also hear it if there is a large load for a while - but nothing irritating. Some inverters will be a lot noisier - unfortunately price will play a part here.
Cheaper Solution
If you have the budget, that would be an amazing solution. 👍 I would say go for it @MdF 
Unfortunately, not everyone has those resources. I have found that sometimes a simpler solution can do the trick. A repeat of @Bobster.'s views, largely. It's a little bit of DIY & no where near the inverter option but could be something to consider. 
Most people are happy with a few basic essentials - lights & entertainment. A trolley inverter can be setup in a corner - not to be moved. It can be used to run all those devices. A simple 12v transformer can then be used to supply LED strip lighting throughout the house. If you get a slightly larger (1.5KW) inverter, you get those portable 650W 1 cup kettles - and a cup of tea can be made.
Alternatively you can use an alarm power supply to give lighting to different rooms. A 2m strip (18w of COB LED strip) will comfortably light a room. An RF transmitter switch works really well.
A couple emergency backup bulbs, I like Aurora, and it ensures you can see where you are going at night.
 

I currently run a Victron 5kw with an FreedomWon 5/4 battery and it works well for me. But the reality is that I hardly ever use the full 5kw. It is used for very brief periods close to it's maximum. If you use 5kw for a decent period of time then I would (absolutely) look for 10kwh of batteries. A single 10kwh is usually cheaper than 2 x 5kwh. You also don't need to worry about matching cable lengths and communication between batteries - usually not an issue.
 
 

I rate the homework youve done here. Good on you. The bms/litthium combination looks after itself, it will cutoff regardlessly at specified low voltage. It will also protect against over discharge, and high chargevoltage. You must just make sure you stay within goid charge voltage limits. 
Fusing is totally important. 

And dont be shy to also add a fuse as close the the battery positive terminal as you possibly can. Rate that fuse twice the size of the greatest of the maximum charge or discharge current. 
Dont wire this fuse in a disconnectable cartridge, hardwire it. 

Thinking of a bit of a hack to provide some lighting during load shedding - using 12v led strip lighting. I would appreciate criticism/suggestions to improve my idea.
The Lights
A couple websites advertise 12v led strip lighting. There is a 'continuous' light option. These use 9w per metre and provide 1000 lumens per metre. These can be mounted in an 'A13' corner mounting profile which fits nicely along the ceiling in most houses. You can also get a RF remote to control the lights. In my view 2m is more than enough to light most rooms.
The Battery
I rate the BlueNova batteries very highly but they are expensive. However, Securi-prod make a 20ah lithium battery that can (supposedly) output 20a. I wouldn't want to push the battery that hard but 8m of led strip lighting (4 rooms) would only need about 6a. Which means that for 2.5 hours of load shedding - and all lights running - you would run a discharge of 75%. I think that should be ok. I don't know if there are other battery brands that anyone can recommend?
The Power Supply - Alarm Power Supply
Sherlotronics make a 6.5A alarm power supply. This power supply can fit a 20ah lithium battery. It provides 6 outputs of about 1a each. Now 2m of led strip light require 1.5a. So the solution is to group the output together to create a single supply of 6a which will supply the led strip lights. I might want to drop the 8m to 7m to include a little bit of margin here. The buzzer can be disabled. The built-in switchover circuitry is also nice.
My only concern is the low battery cut-off is too low for a lithium battery so I am relying on the BMS of the lithium battery. I would also prefer a power supply with a single output - and maybe a 10a rating.
The Power Supply - Solar Charge Controller
This appeals to me as many of them come with a USB charging port, have a programmable low battery cut-off, charging algorithms for lithium batteries and a higher current rating. I am thinking of using a 20a charge controller - to include some additional margin. I would need a DC power source but you can find those very easily. A 10a 12v dc power source should be sufficient - and wouldn't overload a 20a charge controller. The area of concern is that no manufacturer suggests using their device with a non-solar power source - but people are doing it. Are there charge controllers designed/advertised to work with other 12v sources?
Will need to add a fuse on the input in case something goes wrong. From what I understand the charge controller always charges the battery and the demand is always drawn from the battery but these circuits will only be used during load shedding so not too worried about a switch over circuit.
Wiring
Each set of lights would run of their own length of lighting. From my research, 1mm sq ripcord should comfortably handle the 1.5a each circuit will use. The concern would be the voltage drop but a 10m cable length will result in voltage drop of about 0.55v so that won't cause an issue. If I run 20m then a thicker cable would (perhaps) be needed. The voltage drop increases to 1.11v which will slightly impact the brightness of the strips. For safety I should probably add a fuse to each circuit in case there a short-cuit. 
Questions
I would appreciate suggestions/criticism of my idea. It is a bit of a hack to provide some lighting during load shedding. I have seem some circuits for charging, low voltage cut-off and switchover but using an already assembled device seems like an easier (safer) solution.
Thanks