The Electricity Plan Comparison settles the teaser-rate trap: two plans, each with a per-kilowatt-hour rate and a fixed charge, compared at your actual usage, with the break-even usage where the cheaper plan changes places. Enter your usage and both plans' rates and fixed charges (monthly figures are annualized for you), and it names the cheaper plan and the size of the saving.
How It Works
Each plan's cost is usage times its rate plus its fixed charge. The comparison reports both costs, the difference, the cheaper plan, annualized costs and savings, and the percentage saving. The break-even solves the equation where the two cost lines cross: usage equals the difference in fixed charges divided by the difference in rates. Below that usage the low-fixed-charge plan wins; above it, the low-rate plan wins, because the rate advantage compounds with every kilowatt-hour while the fixed advantage does not.
Parameters
| Input | Required | Meaning | |---|---|---| | Usage | Yes | Consumption in kWh for the period (monthly usage is annualized in the outputs) | | Plan A rate and fixed charge | Yes | Per-kWh price and the fixed (supply) charge | | Plan B rate and fixed charge | Yes | The competing offer | | Plan names | No | Labels for the comparison |
Worked example
At 900 kWh of monthly usage: Plan A charges 22 fixed charge, costing 900 x 0.28 + 22 = 0.24 plus 254. Plan B is cheaper by 240 a year, a 7.3% saving. But the break-even is (38 - 22) / (0.28 - 0.24) = 400 kWh: a household using only 300 kWh pays 110 on B, and A wins. The "cheaper plan" is a function of your meter, not of the advertisement, which is why the comparison must run on your usage and not on the retailer's assumed household.
Reading a real electricity offer
Translate the offer into the two numbers this calculator eats. The usage rate may be tiered (a cheaper first block, then a higher rate), time-of-use (peak, shoulder, off-peak prices), or paired with a controlled-load rate for hot water; collapse a tiered or time-of-use tariff into a single effective rate by dividing a recent bill's total usage charges by its total kWh before comparing, and re-run the comparison at your summer and winter usage, since air-conditioning can double consumption and flip the winner. Fixed charges appear as a daily supply charge: multiply by the days in the period to match the usage period you enter. Discounts ("20% off if you pay on time") apply differently by retailer, sometimes to usage only, sometimes to the whole bill; apply the discount to the relevant components before entering them, and treat conditional discounts you might miss as absent.
When the plans tie or never cross
If the rates are equal, the plan with the lower fixed charge wins at every usage and there is no break-even. If one plan has both the lower rate and the lower fixed charge, it dominates outright and the comparison is a formality; the interesting cases, and most real marketing, trade one against the other. The calculator reports a break-even only when the lines genuinely cross at a positive usage, and says so when they do not.
Limitations
The model uses a single flat rate per plan over one period. It does not model tiered blocks internally, time-of-use windows, solar feed-in tariffs, demand charges, green surcharges, or sign-up credits, though feed-in income and credits can be netted into the fixed charge (as a negative) for an approximate comparison. Prices exclude or include taxes exactly as you enter them; keep both plans on the same basis (both with GST or both without) or the comparison inherits the difference.
Frequently Asked Questions
Should I enter monthly or annual usage?
Either, consistently: the cost lines scale linearly, the break-even is identical either way, and the tool annualizes monthly inputs (multiplying by 12) for the annual figures. Enter the period that matches the fixed charges you have.
Why does the cheaper plan change with usage?
Because the two cost components scale differently: the fixed charge is constant while the rate advantage grows with every kilowatt-hour. At low usage the fixed charge dominates the bill; at high usage the rate does.
How do I compare a time-of-use plan?
Compute your effective average rate from a real bill (total usage charges divided by total kWh) for each season, then run the comparison per season. A time-of-use plan can win in summer and lose in winter for the same household.