Hi everybody

So the time has come that I have become pretty fedup with a R2k-R3k per month electricity bills and am now seriously considering solar but would like to get as much independant advice as I possibly can. I reside in Bloemfontein. Still have electric geysers, 2 in fact. One for my main house and one for the currently unoccupied granny flat. I have a 1.1kw borehole pump which is used for about 1.5 hours per day to fill my Jojo tank. Then I have a 2kw water pump for my irrigation system which sees about 1 hours worth of usage a day. Then I also have a 750w pool pump which sees about 2-3 hours worth of usage which I know is too little, but I have become like a electricity scrooge so save as much as I can where I can. Stove is gas, but oven is electrical. All lights in the house are LED. Still have a plasma TV in the lounge which almost never gets used, and then an LED in the bedroom which sees almost constant usage while we are home. I also have quite a monster PC, but prefer PS4 just because its lighter on electricity. 

I use anywhere from 30kwh-50kwh per day. 

The two suppliers in Bloem I am looking at for quotations are these two:

Unilec

Olivia

and I am considering the 15KVA systems from both. I know the pages I linked to are not very specific, but I would just like to know if the prices are ballpark more or less OK?

Step 1 is to replace your geysers with solar geysers. That is an easy win, and you should save 30-40% of your power bill.

What is your cost per kWh of electricity (with fixed costs included), and monthly usage? 

From your total monthly usage you can work out an daily average usage and from there you can size a solar system appropriately. 

Domestic High Winter (ex vat)

Block 1(0-350kWh) - 180.17c per kwh

Block 2(>350kWh) - 218.59c per kwh

Domestic High Summer (ex vat)

Block 1(0-350kWh) - 145.73c per kwh

Block 2(>350kWh) - 168.24c per kwh

Use approximately 30kwh-50kwh per day. Thus 900kwh-1500kwh per month. 

Start with the solar geyser, you should be able to drop 10+ kWh/day from that alone. 

11 minutes ago, DeepBass9 said:

Start with the solar geyser, you should be able to drop 10+ kWh/day from that alone. 

really?  surely this is at a medium to high usage?

I'm with @Pietpower's view. With or without feedback, use the power you are generating.

I comfortably run 2 x electric geysers with timer's to ensure enough hot water for showering 4 people early evening and early next morning. 7.2 kW of panels, so 15 kW is ample/over designed.

Get your timing wrong, and then suffer the consequence.😂

3 hours ago, Dex_ said:

really?  surely this is at a medium to high usage?

How do you manage to use up to 50kWh per day if it is not the geyser?

54 minutes ago, DeepBass9 said:

How do you manage to use up to 50kWh per day if it is not the geyser?

i just meant that can a geyser really use so much power, say it has a 3kw element, 10+ kwh/day would mean it was running constant for over 3 hours? a geyser from what i understand takes around an hour to heat up (this is an assumption i get, it depends on things such as the water starting temp, capacity, the insulation and the end goal temp) - that means it completely heats the water 3 times per day? 

please note I don't want to derail or argue, i am really also just trying to understand.

Step one: Get a the geysers sorted with some "lifestyle" changes that they only have to come on once a day.
Step two: See what loads are on when and see what must be and and when, switch the rest off. Most wastage is when people are asleep.

Now you will have a very good idea of what is left and WHY!?

Keeping SANS and NRS regulations in mind with your local Municipality, go hybrid grid tied. You save THE most this way.

Once you have addressed step one and two and intimately know what is left, you may find that a hybrid grid tied NRS approved 3kva inverter can be added to make a massive dent on your that what is left of your electricity costs - each and every month.

It is not complicated but it is a painful process to first lower consumption to "Need's" level and THEN go grid tied on a 3kva.
Vs
"Want's" level needing a 15kva inverter with the resultant battery bank (ouch) and the huge array (if you have space). We are talking very serious money.

My 2 cents.

Drop me a PM if you want me to first talk you out of solar and then when you understand, I'll talk you back in. 🙂 

6 hours ago, Pietpower said:

Jip it does.  
But heating time and energy use is highly dependent on water use rather than number of geysers and geyser size or temp settings.
Four shower in our house takes 3 hours to heat back up with a 3kW element.  Then some dishes and stuff also takes energy. 
Easily over 10kWh every day.  Probably about half our energy usage.

Other things that adds to energy consumption:
Oven, hair dryers, microwave, aircons, dishwasher, clothes washer if you use hot water, pool/water pumps.

PS Whether it is cost effective or not to add the geyser to the pv system vs replacing it with a solar geyser I don't know.
My reasoning was that adding 6-8 pv panels to the system to cover the geyser load would be easier and cheaper than a proper solar system which still needs electrical backup.

I hear you, I am strongly considering putting my geyser onto my system but i need to work out a way to have it not operate if it is not sunny and there is no mains

Just a titbit. My EV tubes where installed in wot, 2010.

This year it all came tumbling down. I had to:
1) Some tubes needed replacement and guess what? Correct! They are now made anymore!
2) The pump started whining.
3) Geyserwise got damaged with power failures.
4) Geyser - Durathem - started to leak and guess what? Correct! That 10 year warranty ... yea right.
5) Services was done every 2-3 years at about R1k.

So a got a few quotes, about R30k to fix it all.

Don't get met wrong, over the past 9 years we saved a TON of money on the EV tube system. Geez, in +-24 month, with lifestyle changes, we recouped the R24k initial install after Eskom subsidized about R8k.

It just galled me to spend R30k AGAIN and who knows how long it will last this time. Will it last 9 years again? I'm not betting on that no.

So I promptly invested in 4 more panels.
Got a new B rated Kwikot geyser installed outside the house.
Installed a cheap model Geyserwise timer.
And set the timer to go on when I have spare solar - times I alter manually or set for the seasons on the geyserwise.
Plug and forget.

16 hours ago, Dex_ said:

i just meant that can a geyser really use so much power, say it has a 3kw element, 10+ kwh/day would mean it was running constant for over 3 hours? a geyser from what i understand takes around an hour to heat up (this is an assumption i get, it depends on things such as the water starting temp, capacity, the insulation and the end goal temp) - that means it completely heats the water 3 times per day? 

please note I don't want to derail or argue, i am really also just trying to understand.

Heating water is the most power hungry thing that is commonly done. So to raise a 200 litre geyser by 30 degrees is 4.2 x 200 x 30 = 25.2 kJ of energy /3600 seconds = 7kWh. So factor in inefficiencies, heat loss from the geyser and pipes etc etc. and there you have 10kWh. A bigger geyser or more frequent use will only get worse.

Low pressure tube geysers are really cheap, so for R5000 you can get a 200l one. R5000/(10kWh * 30days * R2) = 9 months payback. It will also heat your water much hotter than 30 degrees.

People who are grid tied like TTT are just spoilt. 

Edited August 6, 20196 yr by DeepBass9

1 hour ago, The Terrible Triplett said:

Just a titbit. My EV tubes where installed in wot, 2010.

This year it all came tumbling down. I had to:
1) Some tubes needed replacement and guess what? Correct! They are now made anymore!
2) The pump started whining.
3) Geyserwise got damaged with power failures.
4) Geyser - Durathem - started to leak and guess what? Correct! That 10 year warranty ... yea right.
5) Services was done every 2-3 years at about R1k.

So a got a few quotes, about R30k to fix it all.

Don't get met wrong, over the past 9 years we saved a TON of money on the EV tube system. Geez, in +-24 month, with lifestyle changes, we recouped the R24k initial install after Eskom subsidized about R8k.

It just galled me to spend R30k AGAIN and who knows how long it will last this time. Will it last 9 years again? I'm not betting on that no.

So I promptly invested in 4 more panels.
Got a new B rated Kwikot geyser installed outside the house.
Installed a cheap model Geyserwise timer.
And set the timer to go on when I have spare solar - times I alter manually or set for the seasons on the geyserwise.
Plug and forget.

I'm with you on this one even though i have not tried the EV Tubes, it was just a lot more cost effective to shower in the evenings around 6PM and heat both my geysers again during the day when there is ample PV.

The only change i made was change my elements to 2kw elements to make sure i do not overwork the inverts. these now run from 10am-1pm and the other from 1pm -3pm.

I have an extremely dedicated wife that manages this though. I had it on timers, but she seems to enjoy monitoring and flicking the switches  

 

The EV tubes are just way more efficient, and cheaper than trying to do the same thing with PV.  To get 10kWh per day from PV you will need 1500W to 2000W of panels. 

Edited August 6, 20196 yr by DeepBass9

At my workshop I installed a bath and a low pressure EV tube geyser without any backup element. (The Mrs doesn’t want me coming home in dirty overalls) 

It cost around R3500 back then, and I have to say there is almost always hot water. Sometimes if there are two or three cloudy days, the water will only be warm, but that has happened very few times. The water stays hot for more than 24 hours. 

That geyser is one of the best investments I have ever made. 

So I got my first quote today. 

15KVA Victron inverter with MPTT

20x345w solar panels (brand not mentioned on quote)

2x7.5kw litium batteries. 

R281k excluding installation. 

7 minutes ago, Pietpower said:

Sounds very expensive.   What are the high cost items?
Batteries are probably around R100k?
Solar panels R40k?

Would a 10kVA inverter not be enough? Not sure how Victron work with grid tied vs off grid.

This is acutally my problem with the quote. Nothing is itemised in the quote. Just the total amount of R281k. 🤨

Granted these were the ONLY people in Bloemfontein who respond to email enquiries and actually came out to do a site visit and provide a quote so on that front I do like the service I am getting. 

Regarding the 10kva inverter, I am sure it will work for now, I am just worried it may not be enough when I have a tenant for my granny flat which also has airconditioning. 

Also regarding the grid-tied/off grid comment, I must be honest I havent a clue. I was told the system will be hybrid. 

Edited August 6, 20196 yr by profa

11 minutes ago, profa said:

Regarding the 10kva inverter, I am sure it will work for now,

This guy have quoted you for 6900wh of panels, you can only expect 80% of that after losses. That is 5520 wh. The victron Quattro 8000va (6000w) will allow pass-though current of 100amp plus its own rating. So you can connect any normal 60A or 80A single phase house to it and "add" the 5520wh unto the AC to reduce your bill. With the current planned 6900wh PV array the 15kva 12kw unit will have no benefit over the 6kw unit. 

2 minutes ago, Jaco de Jongh said:

This guy have quoted you for 6900wh of panels, you can only expect 80% of that after losses. That is 5520 wh. The victron Quattro 8000va (6000w) will allow pass-though current of 100amp plus its own rating. So you can connect any normal 60A or 80A single phase house to it and "add" the 5520wh unto the AC to reduce your bill. With the current planned 6900wh PV array the 15kva 12kw unit will have no benefit over the 6kw unit. 

Would it make a difference if I said I planned on installing another 6900wh of panels in the future?

5 minutes ago, profa said:

Would it make a difference if I said I planned on installing another 6900wh of panels in the future?

Yes, now the big inverter makes sense. 

 

1 hour ago, stoic said:

I have an extremely dedicated wife that manages this though. I had it on timers, but she seems to enjoy monitoring and flicking the switches  

Same here, mine just want to not think.

Since day one I made sure the geyser is rated to be outside and not in a box. So we heat during the day, 2kw elements on at set times, and shower the next morning. Temp from 65 down to next morning to 60 or 55. O, the kitchen, that one is on a 50l geyser, no holds barred. That was the biggest saver on keeping the main geyser on high temps during the night.

1 hour ago, DeepBass9 said:

The EV tubes are just way more efficient, and cheaper than trying to do the same thing with PV. 

I agree BUT the 2kw element schedule to set times of the day, I have spare power, is cheaper. On cloudy days the EV do much better yes, but I will not recoup the R30k this time around. So there is that. First time users, form them EV tubes generates a HUGE saving. 

1 hour ago, profa said:

15KVA Victron inverter with MPTT

Would you get it past the SANS and NRS regulations?
3kva gets you damn far if you manage it right, and cost a fraction of that R281k quoted.

8 minutes ago, profa said:

6900wh of panels in the future?

You can do this one day ... IF you can use the power and have the batts to match.

O, as @DeepBass9 said, those low pressure flat panels system, now that is a serious consideration yes.

Me being being spoilt 😂 with grid tie and all that, naaa, I did not want to change piping that works all over the house, for me that was just too much "effort".

1 hour ago, Pietpower said:

You have to compare apples with apples. Different people work with different budgets.
If you go with an off grid system and want to save on capital expenditure then low pressure evacuated tubes is probably the answer.
Persons with grid tied systems aimed at electrical saving and for back up power will most likely prefer high pressure hot water systems at a premium price.

Something else to keep in mind is that an existing pv system would probably not need an extra 1500W of panels but maybe half of that and the other half will come from optimising daytime solar production.

Hmm, the physics don't really add up, unless you are doing little else with the panels in the day, in which case you heating water by the most expensive means possible.

It sounds a bit like my neighbour who decided to get some cows. So he hasn't sorted out his fences, and has no grazing to speak of and it is July. He only needs to put in one farm gate and the cattle will stay on his place, without wandering around all over the place. He has spent the last four weekends building an electric gate so he doesn't have to get out of his car to enter the property. In the meantime one of the cows wandered off somewhere and broke its leg and had to be slaughtered. The point of the story is that instead of going the simplest and most cost effective route, the other route is chosen for reason of convenience, or something.

Edited August 6, 20196 yr by DeepBass9

Because if you think about it, profa is paying R2500-R3000 pm, norrmally about 50% of that is geyser. So install a R30000 super duper solar geyser, save R1200-R1500 per month, you are now paying about half of what you were paying previously and the payback is about 2 years.

The alternative is to pay almost R300 000 for a solar system, to achieve probably an 80% saving with a payback of 8 or 9 years. 

Does not compute.

1 minute ago, DeepBass9 said:

Because if you think about it, profa is paying R2500-R3000 pm, norrmally about 50% of that is geyser. So install a R30000 super duper solar geyser, save R1200-R1500 per month, you are now paying about half of what you were paying previously and the payback is about 2 years.

The alternative is to pay almost R300 000 for a solar system, to achieve probably an 80% saving with a payback of 8 or 9 years. 

Does not compute.

30 000 BTU aircon (and the other smaller ones in the home) is my vice. I like my home being comfortable in terms of temperature.