Approximate Solar Savings

[onlyonekenobie]

Hi all

Considering that we might be close to getting a rebate when installing a solar system, the convenience of not having to worry about level 6 load shedding, coupled with the +-30% electricity price hike in the next 2 years, I am tempted to get solar installed.

My question for those with a solar system, is how much money do you actually save (I know this will vary depending on various factors, I'm looking for a ballpark)? My current electricity usage per month is on average 1000kWh (about R3000).

The system I am looking at would include:

- 8kW Sunsynk or Deye inverter
- 2 x 5kWh batteries
- 8 540W panels

I get mixed estimates from the installers regarding the amount that I will save, and hence what my electricity bill would be at the end of the month, with some saying I would save about 60% (R1800), and others saying 80% (R2400) or more. I have the extra capital sitting in my flexibond, and would like to make sure that the higher bond repayment due to using some of the capital is offset by the savings that I would make.

Any advice would be appreciated!

Thanks

[GCE]

It is very dependent on your daytime usage and setting the system up correctly to utilize the maximum amount of energy produce from the panels and stored in the battery

Don't load your essential side to heavily, to avoid reserving a big portion of battery for load shedding - rather use the battery to feed night time loads

Basic calculation = 8 panels x 540W x 5,5Hrs = +/-23units per day on average
Summer will be more , winter less , dark cloudy days almost none

The 5,5 hrs kinda allows for the non producing days - So the system you are looking at should give you around 690 units per month in summer - During winter it could drop to as low as 300units per month mainly in June , July and Aug

To give you an idea - I have 1 kw of panels facing north and 1kw facing east , so not ideal but it gives 307Kwh in Dec and 111Kwh in June - if it all faced North my winter production would increase by 10 or 20%

Generally Pv with batteries is between 8 to 12 year payback depending on how you manage it - If you actively mange it you will get the payback to 8 years -

[Justloadit]

My experience with a Deye 5.5kW, 10kW battery, and 2.7kW PV panels, set up pool to run from 10H00 to 15H00 daily, wife does washing cloths during the day when sun shines, and I save in Summer approximately 10 to 12KwH and winter 7 to 9KwH.
So I save a third of my bill. I can not save more because I do not use more power during the day when the sun shines, so the panels do stand idle.

I have contemplated getting more batteries and run the load after there is no sufficient sun, but the cost outweighs any saving that I will get.

It is all a balance.

Aaah yes I forgot to mention, my 2 geysers totaling 300 litres run off my own product design, which I sell under the Usedasun Solar geyser name, which is also an extra saving between 7 and 13KwH depending on usage. My website is currently down but is www.usedasun.com. Did I mention most days I get 300 litres of 65 Degree water off the solar. Hopefully in about 2 months it will be up and running again.

It is all about balancing your loads, if you have the geyser element running, that is usually 3Kw off you supply, this becomes a major issue where the whole house is fed through the inverter.
I suggest that the element be changed to 2Kw to reduce this load so that you can used other equipment.

[Isetech]

There is no one size fits all.

The saving will depend on the way you mange your load.

I have one custoer with a 5 kva unit a, a 5kwh battery and a couple panels on the roof, he uses less than 100 kwh of power per month.

Anotehr custoer with the same sytem, they use around 700 kwh per month.

We use ASC's in the DB and ASP's around the house to mange loads.

There are so many factors that determine your saving or usage.

Do you work from home,

do you have ahome executive who uses the washing machine and iron all day, or do you do the washing in the evening and use a tumble drier to dry clothes,

do you run your aircons during the day and night,

Do you have an electric or gas stove,

Do you have an electric or gas geyser,

So many questions.

[onlyonekenobie]

It is very dependent on your daytime usage and setting the system up correctly to utilize the maximum amount of energy produce from the panels and stored in the battery

Don't load your essential side to heavily, to avoid reserving a big portion of battery for load shedding - rather use the battery to feed night time loads

Basic calculation = 8 panels x 540W x 5,5Hrs = +/-23units per day on average
Summer will be more , winter less , dark cloudy days almost none

The 5,5 hrs kinda allows for the non producing days - So the system you are looking at should give you around 690 units per month in summer - During winter it could drop to as low as 300units per month mainly in June , July and Aug

To give you an idea - I have 1 kw of panels facing north and 1kw facing east , so not ideal but it gives 307Kwh in Dec and 111Kwh in June - if it all faced North my winter production would increase by 10 or 20%

Generally Pv with batteries is between 8 to 12 year payback depending on how you manage it - If you actively mange it you will get the payback to 8 years -

Thanks GCE, that is a big difference between winter and summer. Using your formula if I got 10 panels (+- 29kWh) that would get close to my daily consumption which is +-30kWh per day (in summer, maybe a bit less because I'm actively trying to manage usage better). So in summer I guess that would cover most of my bill if my understanding is correct. In winter my consumption last year went up as high as 38kWh per day, if I approximate your power generation loss that would mean I cover about 13kWh per day of that bill in winter - not that great , but still around a R1000 saving I guess.

Man, hard decision. Being partially rid of Eskom would be great, especially as they apparently shed 7MW today without informing anyone that they had officially moved to stage 7. But a R170k investment is a boatload of money. If the monthly saving is good enough I could probably justify it, but there are so many variables...

[GCE]

Thanks GCE, that is a big difference between winter and summer. Using your formula if I got 10 panels (+- 29kWh) that would get close to my daily consumption which is +-30kWh per day (in summer, maybe a bit less because I'm actively trying to manage usage better). So in summer I guess that would cover most of my bill if my understanding is correct. In winter my consumption last year went up as high as 38kWh per day, if I approximate your power generation loss that would mean I cover about 13kWh per day of that bill in winter - not that great , but still around a R1000 saving I guess.

Man, hard decision. Being partially rid of Eskom would be great, especially as they apparently shed 7MW today without informing anyone that they had officially moved to stage 7. But a R170k investment is a boatload of money. If the monthly saving is good enough I could probably justify it, but there are so many variables...

The 29kwh produced is during the day and depending on your usage at night would need to come from stored power - or move night time usage to day , geysers , dishwasher , wash machine

We have found that most systems outperform the assumed calculation method that I gave above depending on angle and direction
My panels facing East hardly produce during winter which is why I drop so low
I have attached another site that I have data for from July which gives you another set of data - This site feeds house , 15KWH of battery and grid for credits so the system utilizes everything that can be produced vs not feeding grid and throttling back in the afternoon which happens on some sites.

With solar and having an App that you can see hourly usage there is a mindset change which relates back to savings in electricity .
People suddenly realize that leaving the heater on for the dogs all night costs money and so they dogs learn to sleep without a heater , baby rooms with heaters on full vs turned down to half or fitting a panel type heater at 500w vs leave 2kw running all night .
Geysers on timers heating in the afternoon vs at 18h00 and again in the morning after showers leaving the geyser off until later in the day when solar can feed the geyser.

If the system is set up correctly and you can monitor and adjust usage, the savings will outperform conservative calculations - Feeding back to the grid after you have utilized also produces savings - Then using time of use settings to your advantage produces further savings