The short answerSpray is cheaper, takes two or three visits over four to six weeks, and works well for a contained infestation in a house. Heat costs three to five times more, is done in a day, kills eggs, and suits severe infestations, cluttered rooms and anyone who cannot wait. In a flat, neither works for long unless the neighbours are checked too.
Every firm has a preference. Firms that have invested in heaters sell heat. Firms that have not sell spray. This post sets the two side by side so you can decide for your own situation, not theirs.
Prices below are from published UK price lists, autumn 2026. Your quote will differ.
Side by side
| Spray course | Heat treatment | |
|---|---|---|
| Typical cost, one bedroom | £150 to £350 | £500 to £900 |
| Typical cost, whole two-bed flat | £300 to £600 | £900 to £1,800 |
| Visits | Two or three, about two weeks apart | One, sometimes with a short check visit |
| Time to completion | Four to six weeks | One day, then a few weeks of watching |
| Kills eggs | Not reliably; follow-ups cover hatching | Yes, if target temperature is reached everywhere |
| Residue left behind | Yes, by design; it keeps working | None, unless the firm adds a light spray |
| Preparation | Strip beds, clear floors, wash bedding | The same, plus removing heat-sensitive items |
| Main failure mode | Missed hiding places; resistance; skipped follow-ups | Cool spots; re-entry from a neighbouring flat |
| Best for | Contained, early infestations; houses; tight budgets | Severe or long-standing infestations; cluttered rooms; flats where time matters |
How spray works, and where it fails
A technician applies a residual insecticide to the bed frame, mattress seams, skirting, furniture joints and other harbourages. Bugs that walk across treated surfaces pick up the product and die over the following days. The residue keeps working for weeks.
Eggs are the weak point. UK professionals do not have a product that reliably kills them, which is why BPCA’s advice describes repeat visits as standard. The second and third visits deal with nymphs that hatched after the first. Skip a follow-up and you have paid for a treatment that was never finished.
Resistance is the other problem. Bed bug populations in some areas tolerate the pyrethroid insecticides most firms use. A good firm rotates products or adds a dust in voids. A poor one sprays the same thing again and blames your housekeeping.
Spray also depends on reach. Behind a fitted wardrobe, inside a divan base, under a laminate floor: if product cannot get there, bugs survive there.
How heat works, and where it fails
Heat treatment raises the air and contents of the room to a temperature that kills bed bugs at every life stage, eggs included. Industrial heaters and fans run for several hours while technicians move air into corners and check sensors placed in the places bugs hide. BPCA’s heat treatment guide explains the method; our heat treatment page covers what the day looks like.
Done properly, heat is finished in one visit. There is no chemical residue and nothing to wait for. For a severe infestation, or a room full of belongings that cannot be bagged and washed, it is often the only realistic choice.
The failure mode is cool spots. A thick mattress, a stack of books, a deep sofa or an external wall in January can stay below the kill temperature while the air around it reads fine. Experienced firms probe these places and run longer. Inexperienced ones pack up when the air sensor says done.
The other failure mode is not the treatment’s fault. In a block of flats, heat clears your flat completely and bugs walk back in from next door a fortnight later. Because heat leaves no residue, there is nothing to stop them. That is why many firms follow heat with a light spray at skirting and entry points.
When spray wins
- The infestation is recent and limited to one bed or one room.
- You live in a house, not a flat, so re-entry is unlikely.
- You can follow the preparation and aftercare for six weeks.
- Budget is the deciding factor.
- The firm is on the BPCA or NPTA register and includes all follow-ups in the price.
Most firms on the Leeds list, the Sheffield list and firms covering Newcastle offer a straightforward three-visit spray course for terraced and semi-detached houses, and for a contained problem it is the sensible buy.
When heat wins
- The infestation is severe or has been going on for months.
- The room cannot be cleared: a hoarded room, a bedsit, a child’s room full of soft toys.
- You need it done now: a tenancy ending, a baby due, a guest house with bookings.
- Previous spray treatments have failed.
- Someone in the home cannot be around insecticide residue.
Heat is more widely available in cities. Firms on the London page, the Leicester list and the Birmingham page offer it routinely. In smaller towns a firm may travel in, which adds to the price.
The honest answer for flats
In a block of flats or a converted house, the method matters less than the scope. If the flats either side are not inspected, both spray and heat are treating a symptom. The best firms ask about the neighbours before they quote and will speak to the managing agent or landlord. Our guide to what happens during treatment describes what a proper inspection covers, and our guide to bed bugs when you rent explains how to get the landlord to coordinate.
Combined treatments
Many firms offer heat followed by a residual spray, or a spray course with a steam pass on the mattress and frame at the first visit. These cost more than spray alone and less than full heat, and for a mid-sized infestation in a flat they are often the best value.
What we would book
For a single bedroom in a house, found early: a three-visit spray course from a registered firm, with a written guarantee.
For a flat with bugs in two rooms and a neighbour who has also seen them: heat for the whole flat with a residual spray at entry points, coordinated with the neighbour’s treatment, booked through the landlord or managing agent if there is one.
For anything that has already had one failed treatment: heat, from a different firm, after a proper inspection.
Whatever you choose, the firm matters as much as the method. We check that every listing is trading, covers the town and whether it is on the BPCA or NPTA register: see how we check. Then find firms on the Glasgow page, the Bristol page or in the A to Z of towns. We never see or pass on your details; you contact firms on their own websites.