To be honest I strongly doubt the surcharge or connection fee is anywhere near high enough. The connection fee is the actual cost of sustaining and upgrading the network and if you think 1 million customers in SA paying $200-300 a year cover's it you misguided. The actual unit charge should be basically applied to the generation only, not distribution. Also if you think a network built decades ago doesn't need more investment, you are misguided. After 30-40 years much of it will need replacing or major upgrades.
20 years ago in Tas, the govt switched to a system from where you were only charged by the kW/h to a mix of connection fee and kW/h. In return the unit charges were reduced significantly. You could reduce your connection fee, back then basically $1/day/house by 2/3 or 1/3 by getting a device installed that limited the maximum amperage draw by the house via switching off major loads. ie fixed heating and hotwater. The idea being to reduce the variation demand on the grid and reduce grid costs.
The ALP/Green's stopped the scheme on election as it was deemed unfair to low power users with people complaining about why they need to pay for power when they don't use any Read "I want to be subsidised by others". And the weak excuse it doesn't encourage people to reduce energy and hence needs to be more expensive so make get more money out of wealthy.
What makes the grid expensive and much of the major upgrades needed in recent 15 years year the demand by house holds to use AC at will as AC is almost standard in Australian houses these days. In 1990, the average house would draw around 10amps tops on a non-winter night. A few amps for TV, lighting other items and random minor use of stove, kettle, vacuum cleaner, hair drier etc. Most rooms in the older house would be lucky to have two single outlets per room and usually one vacant. Now while some things have improved in efficiency, AC's are pretty standard and you can see this on SA's daily load variation in summer with houses now pushing 20-25amps. 1200MW to 3300MW in 8hr, far greater swing than any other state. This is a WTF situation. So you need a grid that can take a minimum 3 x increase in demand over nominal plus a buffer so the ever complaining voters don't go black.
Even today SA is going from 1100MW to 1700MW 155%, meanwhile NSW is 140%, other states less.
I'm also sure the connection fee is being used to recoup funds from those cutting their energy demand to offset rising prices.
The good news is for those wanting to go stand alone, the higher the connection fee, the more viable it is to disconnect when the technology catches up.