Swell Sport · Practical guide

Comparing two sauna bills fairly after changing your routine

A lower bill does not automatically prove a better sauna routine, and an unchanged bill does not prove nothing improved. Compare cycle energy and price separately.

Swell Cedar Cube 2 in a home setting.

Define what changed

Write down the old and new routine, the dates and the question you want answered. Perhaps there are fewer reheats, a different household slot or fewer cancelled cycles. Keep the comparison about those practical changes rather than trying to infer health benefits from frequency or duration.

For each period, record complete heating cycles, metered sauna kWh, powered-stage boundaries, starting conditions, equipment settings and unusual events. Count a continuously enabled window as one cycle even when several people use it separately. Do not switch between counting people and counting heating starts halfway through the exercise.

Use two normalisations

First divide total sauna kWh by complete cycles. Then reprice both periods at the same comparison rate, or at the same time-band schedule if suitable interval data exists. Government guidance distinguishes fixed charges from variable use charges and explains that time-of-use prices change by period. These bill structures make a raw dollar comparison incomplete. ^[1] ^[2]

Use a separate row for grid-import energy if solar or batteries are involved. Total circuit consumption is not interchangeable with grid purchases. Government guidance distinguishes on-site solar use and exported surplus credited to the bill. A changed export/import pattern can affect dollars without showing a more efficient cabin. ^[3]

An unchanged cost can conceal lower consumption

Suppose the first invented period has 7 complete cycles using 42 kWh, or 6 kWh per cycle. The second has 6 cycles using 30 kWh, or 5 kWh per cycle. At illustrative rates of $0.30/kWh and $0.42/kWh respectively, both usage totals cost $12.60. The unchanged amount alone would hide changes in both cycle count and average energy.

At a common illustrative $0.30/kWh, the second period would instead cost $9.00. This repricing helps explain the arithmetic; it does not establish what caused the lower consumption. These are invented readings and rates, not current retailer prices or evidence that a particular routine saves energy.

Keep confounders in the conclusion

Compare similar starting conditions, selected settings and complete powered windows where possible. If one period included different weather, guests, interrupted starts or missing readings, keep those notes beside the result. Exclude incomplete records only with a stated reason and show how many remain. Do not remove an expensive cycle merely because it spoils the average.

Finish with a narrow conclusion: ‘In these logged cycles, energy per complete cycle was lower, while the tariff increased.’ Avoid ‘the new routine caused a permanent saving’ unless the evidence genuinely supports it. Continue recording if the sample is too different to answer the original question. The useful deliverable is an honest comparison sheet, not a claim that fits a preferred outcome.