Tracking rising electricity costs in Modbury, South Australia

Info

These are the prices listed on my electricity bills, and are before GST has been added to them (+10%).  Since it's next to impossible to get any electricity costs from a website without also giving them your address, it's a fair bet that they charge different prices per district (i.e. not the same price for everyone in the whole state, perhaps not even the same pricing for the metropolitan area).  And as our consumption has gone down (with more efficient electrical devices, and home solar power generation) the costs have gone up, as they still want to earn x millions of dollars per year, regardless of our actual usage.

Electricity usage costs are in cents per kilowatt hours (the prices they gave, as typed above, are before tax has been added).  For example, a price of 50 ¢/kWh means it costs 50¢ for 1000 watts for an hour.  It would cost half that to use half the amount of power, or for half the amount of time.  Or double that for twice the amount of power, or for twice the time.

The supply charge is a fixed cost per day.  It is charged whether or not you use any electricity.

Pricing changes are taken from the amounts listed on each bill, and letters received between bills informing me of price changes.  Although I'm billed quarterly, some bills had one or more price changes in the middle of the quarter.

Before 15 March 2022 there were only two electricity prices:  One for all day, every day, for anything and everything using electricity in the house.  And another for a timer-controlled loads (usually, for hot water heating overnight).

After that date, the day got split into timezones with different pricing.  Supposedly to encourage you to use your power during the cheaper periods, instead, when the power network was under-utilised.  But more likely to make you pay more for when you have to use your electricity.  You don't really have much choice if you have to run the washing machine before you leave for work, and what time you cook your dinner.  I'd hazard a guess that most houses are empty during the day, when you're at work or school, so you can't really take advantage of the slightly cheaper middle-of-the-day “shoulder” rate.  About the only thing that can have its time of electricity use moved around is a hot water heater, if can store enough hot water for a whole day's use.  You're probably going to be using the most power during the afternoon, evening, and overnight (cooking, heating, air-conditioning).

Controlled load is for things like water heaters running on a timer controlled by the electricity meter to run at a time the supply company wants it to run at.  They offer a discounted rate for this in an effort to try balancing the load on the power network across the entire day.  Industry is their greatest load, and that's mostly throughout the day, but night-time has very little load (home electricity usage is miniscule in comparison).  Traditionally this was a night-rate for running your hot water storage heaters, which relies on them being able to heat up the water in the allotted time, and not lose too much heat during the rest of the day.  Other countries also use this for house central heating.  In December 2022 AGL expanded it to also include another operating time during the day, supposedly to counteract home solar power generating more electricity than was being used (instead of remotely turning off people's solar power invertors, which caused protests).  Although there will be an element of doing this to make you use more electricty so they pay you less for generating it (as more people had alternative power sources to use, they were selling less electricity).  They'll also push their prices up to make up for those sales losses.

The controlled load time can be varied (remotely) by the supply company at any time (by sending control signals).  And the electricity meter might not correct its clock when daylight savings is in effect, so it's idea of the current time may be an hour wrong.  Not correcting its clock for daylight savings will affect all of the different time-of-day zones that the meter charges for, making it even harder for you to plan cheaper use of power.

Generally speaking, the power companies only allow things like storage water heaters to be a controlled load device.  It's something that's a high current use, and has to be okay for it to be switched off for long periods of time.

Loads

42 inch Plasma TV:  Average 100–150 watts, so using 125 watts for this calculation.  Not used every day.  Average 3 hours when it is on at night, at the most expensive electricity rate.  The (3 hours per day) daily running cost is about 18¢ plus GST.

Basic personal computer:  Running 24 hours, about 60 watts nominally, around 100 watts occasionally, so using 80 watts for this calculation.  It's not a high-powered gaming PC, and most computers do not consume the amount of power that their supply is rated at being capable of producing (so ignore the power rating on its supply for calculating its power consumption, you'll have to actually measure it).  The daily running cost is about 78¢ plus GST (approx 86¢).

Delongi (HM4K TRD41200MT) oil-filled radiator:  Marked as 1100–1200 watts, but measured as actually drawing 2 watts (off, with only its timer-clock motor running), 1100 watts (on power setting 1), 1400 watts (on power setting 2), 2500 watts (on power setting  3).  It has a thermostat, and spends most of its time off, with the thermostat only kicking in to warm it up again every now and then.  The maximum power is well in excess of what you expect it to draw based on the rating label.  Those are rounded-off figures, and heaters can use more power than they're labelled at (supply voltage will affect power draw).  This can overload a circuit, especially when several are in use.  If you have an older house where several power points are on the same fuse or circuit breaker throughout the property, you have to use less power on each heater to avoid tripping them, or risking starting an electrical fire in the wiring.  Mainly used evening and overnight in winter only, with some use in mornings, and some use all day during very cold weather.

That's for a heater with no thermostat, or the thermostat turned all the way up (it will run continuously using the same amount of power all the time).  But If you had a heater with a thermostat that switches the heater on and off to maintain the temperature, and it only spent a third of its time with the heater powered on (for the sake of an example), then the cost would be a third ($3.41 + GST = $3.75).  And it'd cost even less if you weren't running it all day.

This is amongst the various reasons I don't like portable fan heaters.  When their thermostat switches off you feel a significant temperature change, so people turn it right up to run constantly.  And they clog up with dust and become a nuisance for asthmatics.  Whereas an oil heater has thermal mass, giving a more consistent heating effect where you don't really notice it cycling on and off.