The honest answer is “it depends how long you run it”, which is true and useless. So here are the actual numbers for our two machines, worked through into evenings and pennies, with the assumptions shown so you can adjust them for your own house.
Both Wisp machines cycle on and off rather than spraying continuously, and the figures below are averages across that normal cycle, not a continuous-spray rate.
Most people run a bedroom or living-room machine for three or four hours in the evening, not all day. On that basis:
| Bottle | Running hours (Mini) | At 3–4 hrs an evening | Cost per evening |
|---|---|---|---|
| 10 ml (£12) | ~10 hours | ~3 evenings | ~£4 a night |
| 50 ml (£21) | ~50 hours | ~2 weeks | ~£1.50 a night |
| 125 ml (£45) | ~125 hours | ~5–6 weeks | ~£1.10 a night |
The 10 ml is really a sampling size — enough to live with a fragrance for a few nights before you commit to a larger bottle. The 125 ml is where the cost per evening settles down to about a pound.
A Fragrance System running eight hours a day, five days a week, uses roughly 90–100 ml a week. A 125 ml bottle is therefore a bit over a week of trading; most businesses keep two or three on the shelf and rotate fragrances by season. Because the machine covers 430–500 m², one unit usually does a whole floor, so the per-day cost of scenting a decent-sized retail space works out at a few pounds.
A good scented candle burns for 40–50 hours and costs £30–£60, which is roughly £1 an hour, and it only scents the room while it is lit and you are watching it. A plug-in refill lasts a month or so at around £5, but the fragrance fades week by week as the heat cooks the lighter notes off. A 125 ml bottle of fragrance oil at £45 gives 125 running hours — about 36p an hour — and the last hour smells the same as the first.
Start with 10 ml if you are new to a fragrance, 50 ml if you already know you like it, and 125 ml for the fragrance you reach for every night. All three sizes are on every fragrance page; the Fragrance Finder will help if you have not chosen one yet.
About 10 hours of running time in the Wisp Mini — roughly three evenings at three to four hours a night. It is intended as a sampling size.
Around 125 running hours in the Mini, which is five to six weeks of evenings at home. In the larger Fragrance System, running eight hours a day, it is a little over a week.
At home, with the 125 ml bottle and a three-to-four-hour evening, about £1.10 a night. In a shop running the Fragrance System all day, a few pounds a day for a whole floor.
No. Cold-air diffusion does not heat the oil, so the scent in the last millilitre is the same composition as the first. Fading over time is a plug-in and candle problem, not a cold-air one.
