Hi everyone,

So been reading (mostly on this forum which is amazing) and want to confirm a few things and validate my understanding. We're looking at getting some solar in both to combat load shedding as well as start saving on the Eskom bill.

Consumption

We use about 650 kWh in summer, and around 850 kWh in winter. I did a quick walk around the house and would put the below as my consumption

1. Essentials at 3.1kW - Plugs in lounges (PC, laptops, screens, modem/routers, TVs, sound systems) + lights (LEDs) + fridge
2. Security system in place, plugged in socket in baby's room (don't know how much it uses)
3. 200L Kwikot with 4kW element on a timer
4. Regularly used - 1kW dishwasher, washing machine, 1.5kW Air fryer, Nespresso, 1.5kW fin oil heater in baby's room at night (not on max though)
5. Gas hob in place. Electric oven but very rarely used - the air fryer is usually used

The Plan

Currently looking at getting a 5kW hybrid, a 4.8kW battery, and solar panels (max possible) if budget allows. If budget doesn't allow then we'll put in the panels after 6 months - 1 year

Ideally looking to have the geyser on the same system. Don't want to have a separate project on the geyser (heat pump, etc), and happy to change timer. Alternatively I can look into a lower kW element. Logic says it will simply take longer to heat up

Dishwasher, washing machine can be used at appropriate time as well.

Fin oil heater from what I read use the 1.5kW to heat up the oil to set temp then go off till oil temp drops. In general these don't use 1.5kW constantly so can see how long it survives off battery

So bedrooms, lounges, fridge socket on essential load, the rest on non-essential

Clarifications

First of all, does the above plan make sense and is it feasible?

And for some of the more specific questions

1. The kW rating on the inverter e.g. 5kW, 8kW is the power is able to convert from DC to AC i.e. the total solar power or battery power is can use?
2. So above means I should ensure the essentials are below the inverter rating AND any battery output limitations?
3. During none-load shedding situation and peak sun, the excess solar energy can be used on the geyser/dish washer/washing machine with any shortage pulled from Eskom?
4. If set up batteries to be prioritized at night (except for when load shedding is expected), they will be used first and only switch over to Eskom once minimum set charge is reached?
5. Would a lower kW element assist in spreading out the energy by lowering power requirement, so during peak sun it would make use of solar (assuming other loads are also low at the time)?

Thanks

 

 

Your 3.1kw surely must be maximum draw at a point in time? - reason i say this is because i have a similar setup and our baseload is about 700w when TV, Fridge, all computer items etc are on. Load goes up by 800w when pool pump goes on and then fluctuates between 1.4kw to 5kw if both washing machine and dishwasher are on at the sametime - we manage the whole house on a 5kw Sunsynk.

The battery draw will depend on the batteries chosen, most are 0.5c so you'd only get half the rated output, so 2.4kw on a 4.8kwh battery. If you get 1C batteries (hubble) then you can get the full amount

During non-loadshedding your assumptions are correct and you can change this logic on the fly

If the sun is out you can run the whole house on panels (depending of course on your kwp rating) - if your CT coil is setup correctly then yes any excess can power the geyser and other non-essentials

 

@josievich, I have a 5 kW Sunsynk, 6.4 kWp of panels and a 4.8 kWh Pylontech, my load parameters are essentially the same as yours, plus I have 2 geysers and pool pump and the system works beautifully.

If you are located in Cape Town, you are welcome to come and check out my installation

22 minutes ago, mzezman said:

Your 3.1kw surely must be maximum draw at a point in time?

Correct, that is the peak and would likely never reach close to that. But sounds like the 5kW is more that enough for my situation then

 

24 minutes ago, mzezman said:

The battery draw will depend on the batteries chosen, most are 0.5c so you'd only get half the rated output, so 2.4kw on a 4.8kwh battery

And if I add additional batteries in the future I take it the output will go up appropriately? So 4.8kW total out if 9.2kWh batteries in total?

 

24 minutes ago, Tariq said:

@josievich, I have a 5 kW Sunsynk, 6.4 kWp of panels and a 4.8 kWh Pylontech, my load parameters are essentially the same as yours, plus I have 2 geysers and pool pump and the system works beautifully.

If you are located in Cape Town, you are welcome to come and check out my installation

That's great to hear - I'm looking at a similar system. In Joburg, but I appreciate the offer

Yup - 5kw should be enough. Correct on the additional batteries - i recently added a second 4.8 (9.6 in total) and can now pull just under 4.8 from the batteries

Also happy to share any charts / experience with you - even a site visit (in PTA)

1 hour ago, mzezman said:

Yup - 5kw should be enough. Correct on the additional batteries - i recently added a second 4.8 (9.6 in total) and can now pull just under 4.8 from the batteries

Also happy to share any charts / experience with you - even a site visit (in PTA)

Thanks, and charts you can share will be great. Been having a look at some of the charts on the forum as well

Solarman Charts

 

Solar Assistant Charts

 

 

Delete this please

Edited March 14, 20224 yr by zsde
forgot the quote

3 hours ago, mzezman said:

Yup - 5kw should be enough. Correct on the additional batteries - i recently added a second 4.8 (9.6 in total) and can now pull just under 4.8 from the batteries

Also happy to share any charts / experience with you - even a site visit (in PTA)

Can I ask you how long you had your first battery for before adding the second?
I am considering a second battery too but am hesitant in terms of the elapsed time and cycle difference between the current and a new battery.
How long did you have your first one before adding the second and what is the cycle count difference?

1 hour ago, zsde said:

Can I ask you how long you had your first battery for before adding the second?
I am considering a second battery too but am hesitant in terms of the elapsed time and cycle difference between the current and a new battery.
How long did you have your first one before adding the second and what is the cycle count difference?

In terms of lithium batteries it makes no difference when you add a second or more batteries ,unlike lead acid.

17 hours ago, zsde said:

Can I ask you how long you had your first battery for before adding the second?
I am considering a second battery too but am hesitant in terms of the elapsed time and cycle difference between the current and a new battery.
How long did you have your first one before adding the second and what is the cycle count difference?

I added the 2nd battery 3 months after the 1st. To @Nexuss's point - its less of an issue with Lithium compared to LA. I do not have the cycle numbers on me unfortunately - waiting on Solar Assistant team to get a Dyness battery integration going but the BMS reports a good SoH

22 hours ago, josievich said:

Hi everyone,

So been reading (mostly on this forum which is amazing) and want to confirm a few things and validate my understanding. We're looking at getting some solar in both to combat load shedding as well as start saving on the Eskom bill.

Consumption

We use about 650 kWh in summer, and around 850 kWh in winter. I did a quick walk around the house and would put the below as my consumption

1. Essentials at 3.1kW - Plugs in lounges (PC, laptops, screens, modem/routers, TVs, sound systems) + lights (LEDs) + fridge

That seems high. I run a similar amount of gear at nights, and we don't get above a kw. That's two fridge/freezer combos, a deep freeze. Usually only one TV actually on at a time. No decoders (I recently cut the cord). OK... so if you have multiple TVs on and multiple PCs as well then that's going to push the total up a bit. But you'll be OK I should think.

In fact you can back up a TV, decoder, a couple of lights, wifi and charge phones with a UPS for costing 10 grand max. I understand you are working towards something greater, but I think you are overestimating the load here.

22 hours ago, josievich said:

Ideally looking to have the geyser on the same system. Don't want to have a separate project on the geyser (heat pump, etc), and happy to change timer. Alternatively I can look into a lower kW element. Logic says it will simply take longer to heat up

4Kw is too much. You geyser is running, somebody turns on the kettle or the microwave... bingo! You are exceeding the 5kw limit on backed up circuits. I am famous on this forum for recommending a heat pump (less draw for less time to heat a geyser), but this is not the only way. 

 

22 hours ago, josievich said:

Dishwasher, washing machine can be used at appropriate time as well.

Unless you're using cycles which heat the water, the washing machine won't draw that much. A dishwasher doesn't draw that much MOST of the time, but it will heat the water up at some points of it's cycle, and although this doesn't take long, it's another thing that can add up with other loads to put you over the 5Kw limit.

Remember that the system is effectively backing up the backed up loads all the time, it doesn't switch them to grid when times are good. So even on a bright day when you have lots of juice in the batteries, you can overload the system.

What one needs to do when converting to backup or solar systems, is to have some kind of tool that will show you not just total load for the day, but also when the electricity was used. You can even play games, like let the graph settle down and then go turn on the pool pump and observe the difference. If you watch the chart closely at first, you will soon learn what is turning on when and how much it is drawing and can start moving loads around so that everything runs, but the 5kw limit is never used.

To maximise the benefits of the system you will need to have some discipline and change your routines a bit. You have to literally make hay while the sun shines.

22 hours ago, josievich said:

Fin oil heater from what I read use the 1.5kW to heat up the oil to set temp then go off till oil temp drops. In general these don't use 1.5kW constantly so can see how long it survives off battery

So bedrooms, lounges, fridge socket on essential load, the rest on non-essential

Clarifications

First of all, does the above plan make sense and is it feasible?

And for some of the more specific questions

1. The kW rating on the inverter e.g. 5kW, 8kW is the power is able to convert from DC to AC i.e. the total solar power or battery power is can use?

Usually it refers to what the inverter can deliver from the battery pack.

22 hours ago, josievich said:

 

1. So above means I should ensure the essentials are below the inverter rating AND any battery output limitations?

Yes

22 hours ago, josievich said:

 

1. During none-load shedding situation and peak sun, the excess solar energy can be used on the geyser/dish washer/washing machine with any shortage pulled from Eskom?

Depends on the inverter. My Goodwe behaves as you describe if I run it in the default mode. Most hybrid inverters will do this. 

22 hours ago, josievich said:

1. If set up batteries to be prioritized at night (except for when load shedding is expected), they will be used first and only switch over to Eskom once minimum set charge is reached?

Most good hybrid systems will allow you to have a rule something like "allow the batteries to discharge to 40% left, if there is grid available, then draw from grid." That gives you something in reserve if there is an outage at any time.

22 hours ago, josievich said:

1. Would a lower kW element assist in spreading out the energy by lowering power requirement, so during peak sun it would make use of solar (assuming other loads are also low at the time)?

Thanks

As stated above, that 4Kw element has to go, or it has to be put on the non-backed up circuits, or you need to find another way of heating water.

My house used to draw around 450 kw/h a month. With 10Kw/h of batteries, on a sunny day, we use less than a kw/h per day from the grid. We have a full gas stove. What isn't backed up is the outbuildings, so when there's an outage we loose the appliances in the scullery, the pool pump, and the 2nd geyser. Everything else (including electric fence) is backed up.

So you can have quite a low degree of interruption in your life, AND save money.

In terms of the latter: You say you are in Jhb. What tariff are you on? Remember that on the default post-paid tariff you are paying flat fees every month, even if you use no power. If you want to maximise your savings then consider switching to pre-paid. At your level of usage you would save money on pre-paid anyway. It is expensive for a couple of months because you have to pay off the post-paid account whilst feeding the meter, but after a couple of months when the post-paid account is finalised you will be saving. 

@Bobster Thanks for the comprehensive response. A couple of notes from my side

1. The 3.1kw is the absolute max, based purely on looking at the power ratings of the devices and assuming all are on once. Definitely will not need that at once
2. The plan with the geyser (for now at least) is to have it on the non-essential and supplement with Eskom when required. I gather a decent hybrid inverter would blend that properly (Sunsynk, Dewe, etc)? Maybe later on I can look at changing that up, but from a priority perspective, having the backup for essentials (with solar as a bonus) is a priority. I don't mind losing the geyser during load shedding. Can always manually turn it on later when power is back
3. Already on prepaid - spending about R1.5k/month now in summer, typically R2.2k last winter