Using more pre paid electricity after installing an inverter battery combination, no solar 

Yes

There are power losses between charging and discharging,and the inverters also tend to have a % of power loss over direct use. 10% tends to be a fair average from my experience

Specifically for me I had a week period where I only had an inverter and batteries (waiting for panels) And yes I also was surprised on the amount of "overhead" this introduces and my electricity usage went up +-2.5kwh units per day. I have a SunSynk 8kw inverter and it uses +-100W at a time even with trickle grid feed set to zero as luckily I still have an old analogue meter and not prepaid.

Retrospectively, thinking about it makes a lot of sense, but rarely one thinks about this "tax" before getting a system. I think its something that needs to be made known beforehand by installers/distributors to educate people and allow them to budget for the +-10-15% electricity usage increase. I understand there are a lot of reasons why one can not add solar panels to a system (costs, building laws, etc), but ideally a system should have some sort of PV input to complete the picture.

 

Definitely noticed an increase my side too. When we moved onto a Prepaid meter over a year ago, I started tracking my daily unit usage - and it was around 7-8 units for the house per day. The DAY we had our inverter and battery installed, it's gone up by the same +-2.5 units a day. I've set my inverter to only charge the battery at midnight for a few hours, but it's for sure that extra power needed to charge the system. Looking forward to the reduction when panels are in

2 hours ago, willem olivier said:

Using more pre paid electricity after installing an inverter battery combination, no solar 

yip, that's to be expected as you have no "free" power to charge up the batteries.
So you effectively paying to charge up the batteries for the time they were used to cover loadshedding and this usually comes with a bit of losses which is where that extra cost is coming from.

2 hours ago, jgdt said:

Specifically for me I had a week period where I only had an inverter and batteries (waiting for panels) And yes I also was surprised on the amount of "overhead" this introduces and my electricity usage went up +-2.5kwh units per day. I have a SunSynk 8kw inverter and it uses +-100W at a time even with trickle grid feed set to zero as luckily I still have an old analogue meter and not prepaid.

Retrospectively, thinking about it makes a lot of sense, but rarely one thinks about this "tax" before getting a system. I think its something that needs to be made known beforehand by installers/distributors to educate people and allow them to budget for the +-10-15% electricity usage increase. I understand there are a lot of reasons why one can not add solar panels to a system (costs, building laws, etc), but ideally a system should have some sort of PV input to complete the picture.

In Jan 2023, SunSynk released some new firmware that allows the inverter to enter a "low power mode".
This low power mode is designed for countries that have little sunlight in winter.
When in low power mode the +/- 100W decreases to a few watts to save the batteries end enters a bypass (straight through) mode.
The downside is that in the event of an outage (load shedding), it takes the inverter a few minutes to wake up.

Not sure this new "low power mode" would be of any benefit with South African regular load shedding.

Check the SunSynk youtube channel for details.

 

Edited February 28, 20233 yr by system32

The inverter definitely consumes power on its own. There is two losses, the standby losses just to have the inverter on and the charger maintaining the float charge for the batteries. And the "efficiency" losses of energy that is converted (charging/inverting). Standby seems to range between 30-100W, depending on the brand and size of the inverter. And efficiency loss 3-10%, in the inverter. Your battery chemistry will have its own cycle losses.

So for a fairly low consumer like @ShanoMac, the standby loss of 100W x 24h works out to 2.4units extra on the 8kWh prior. That's about a 30% increase! That's without any loadshedding charging/discharging at all - just owning the system.

For heavier consumers, the standby dilutes away and you are left with the much lower percentage of inefficiencies.

These losses are still there if you have solar. But since the panels don't send you a monthly bill, it's not that noticeable 😉