A power bill is two numbers: a daily charge you pay whether the house is empty or not, and a rate per unit. Two plans with those in different proportions are two straight lines, and two straight lines cross exactly once.
So “which plan is cheaper” has no answer until you say how much you use — and the plan with the lowest advertised rate is routinely the more expensive one for a household that does not use much.
The other half is that your usage is not a number, it is last year's weather. A difference smaller than the range your own usage moves through is not a saving, and this page will say so instead of naming a winner.
Nothing is uploaded. The arithmetic runs here for one request and nothing is written down.
At 7,000 units a year, which is inside the range your own usage moves through. Two plans that swap places when the weather changes are one plan.
Cost against usage
One line per plan. The shaded band is the range your usage moves through from year to year; if two lines cross inside it, the ranking between them is weather, not a decision.
The bills, side by side
Split into the part you pay for existing and the part you pay for using. The last two columns are the same bills at the bottom and top of your own range.
| # | Plan | Daily | Rate | Fixed part | Units part | A year | At 6,300 | At 7,700 |
|---|---|---|---|---|---|---|---|---|
| 1 | Standard | 145.0c | 28.0c | $529 | $1,960 | $2,489 | $2,293 | $2,685 |
| 2 | Low daily, higher rate | 69.0c | 32.0c | $252 | $2,240 | $2,492 | $2,268 | $2,716 |
| 3 | Low rate, high daily | 220.0c | 24.5c | $803 | $1,715 | $2,518 | $2,347 | $2,690 |
Standard comes out $3 a year ahead of Low daily, higher rate — but they swap places inside the range your own usage moves through, crossing at 6,935 kWh a year. Pick either one on something else: the fixed term, the exit fee, whether the retailer answers the phone.
Low rate, high daily has the lowest rate at 24.5c a unit and costs $2,518 a year — $29 more than Standard. Its daily charge is 220c against 145c, which is $274 a year before a single unit is used. It would take 7,821 kWh a year to be worth it.
The Low Fixed Charge regulations capped the daily charge for households under 8,000 kWh a year (9,000 in the lower South Island). That cap is being phased out, so the daily charge on a low-user plan rises each year on its own. Nothing here assumes a schedule for that — the daily charges above are the ones you typed in — but it is why last year's comparison does not settle this year's.
Where they cross
Two plans are two straight lines, so each pair meets at exactly one usage. That number is the whole comparison: it does not depend on you, only on the two plans.
- 6,935 kWh a year — below that Low daily, higher rate, above it Standard
- 7,349 kWh a year — below that Low daily, higher rate, above it Low rate, high daily
- 7,821 kWh a year — below that Standard, above it Low rate, high daily
What it does not know
It does not know about time-of-use. A plan with free hours, a night rate or an off-peak window is not two numbers, and pretending it is would flatter it or damn it depending on when you run the dishwasher. Those plans need half-hourly data, which is a different tool.
It does not know about prompt-payment discounts, sign-up credits or exit fees. A $150 joining credit is a real $150, and it happens once; the daily charge happens 365 times a year forever.
It does not know about your lines company. Distribution charges differ by network and are usually inside the numbers above, so plans from two regions are not comparable even when both are on this list.
It assumes next year looks like last year. A new heat pump, a baby, or somebody moving out moves the usage further than any plan difference on this page, and the crossover numbers are the only figures here that do not care.