The cheapest way to keep a room smelling good

These five formats are usually compared on shelf price, which is meaningless - they last for wildly different lengths of time and two of them draw power.

So: cost per hour of use, computed the same way for each. Consumable price divided by its usable life, plus electricity where there is any.

Not a judgment about candles, just arithmetic. A candle is consumed as fuel. Every hour it burns, some of it permanently ceases to exist.

A wax melt is not consumed - only the fragrance leaves. The wax is still in the dish, and while that does not make the fragrance free, it means you are buying only the scent rather than the scent plus its container plus the fuel to release it.

There is a third option people miss: a candle warmer lamp warms a jar candle from above without burning it. The candle releases fragrance and is not consumed, so the same jar lasts far longer than it would burned. If you already own candles you stopped burning, that is the cheapest use of them available. See candle warmer lamps.

Worth saying on a page whose commercial purpose is to sell wax: ventilation and cleaning are free, and they work better than any of the five.

Most rooms that need scenting have a source. Bins, a litter tray, damp laundry, an old rug, last night's cooking, a closed-up room. A fragrance product laid over an active source produces two smells rather than none, and the brain keeps separating them.

Open a window for ten minutes. Deal with the source. Then a modest amount of fragrance does something achievable, and you will need less of it. That is not us being high-minded - a warmer that works properly on one cube costs half what one fighting a bin costs on three.

For odor specifically, a melt formulated to neutralize rather than mask is a different product from a fragrance melt. See wax melts for pet odor.

If wax melts are the format you want, this is how to run them for as little as possible.

• A low-wattage plate warmer with no bulb. The 10 W model we index costs about $3.72 a year at six hours a day, and there is no consumable to replace. A 25 W bulb warmer is roughly two and a half times that plus bulbs.
• A timer, built in or a plug-in outlet timer. The cheapest durability upgrade available, because a warmer running while you are asleep or out is spending wax for nothing.
• The largest pack of a scent you have already tested. Cost per hour falls with pack size where hours are published. Test small first - a large pouch of something you dislike is not cheap fragrance.
• Buy from a brand that publishes hours. Otherwise you cannot tell whether you got a bargain.
• Store it sealed, cool and dark. Fragrance evaporates from solid wax at room temperature, so a badly stored bulk buy loses the saving. Storage and shelf life.
• Do not overfill. More wax gives a cooler pool and less fragrance. Using three cubes where two would do is paying 50 per cent more for a worse result.

Buy unbranded bulk wax with no maker named. It looks unbeatable per ounce and it fails the actual test: with no published hours you cannot compute cost per hour, so "cheap per ounce" is being compared against a different measurement. A weak melt at half the price that needs twice the dose is not cheaper.

The stronger objection is that you cannot see an ingredient list. If there is a cat in the house, that means you cannot check the product against the Pet Poison Helpline or VCA lists of oils toxic to cats - for the sake of a few dollars on a product you vaporize into a room the animal lives in. See wax melts and cats.

Run a warmer continuously to avoid switching it on. Wax is spent within hours; the rest is heating an inert disc. It is the single most expensive habit in this category and it buys nothing.