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It's pretty easy to check that . . . 2 ways, depending if you are on old analogue metering, or digital smart metering and have been on it for at least 2 years . . .
Analogue meter
Get your last 4 Origin bills (to get a year round view of usage)
Find an AGL plan that best suits your homes power usage, time of day you use power especially, HWS, etc
Compare tariffs for all your various times of use (as applicable)
Compare daily supply charge
Maybe jot this all down on paper in 2 (or more) columns, then use a calculator or brain power to work out based on what your usage is in kwh for each season (quarter or monthly), to compare with the AGL best plan tariffs / supply charge, you should then be able to see if the comparison is more or less.
Digital meter, with more than 2 years data
Go to energymadeeasy.gov.au
Type in your address and click it as it comes into the automatic listing
(You might need your NEM number fro your bill, can't remember.)
Compare your rates / charges with other plans with AGL and / or other suppliers
Make sure you at least look at the various tariffs and supply charge to ensure you know what is cheaper, but this at least uses your actual data figures from the past 2 years to compare, if it is available.
You could probably call AGL on 131245 and they should be able to use your NMI number on the bill, or your figures with usage, and offer you the best plan for your needs, give you a comparison price, or at least tell you the tariffs and supply charge to see how they compare to Origin.