⏱ Read time: 6 min 📊 Difficulty: Beginner 🔧 Setup time: 15 to 30 mins 👷 Manpower: 1 person
There are two types of cooling equipment hire that come up in almost every summer conversation at HSS DIY. The evaporative cooler, which uses water evaporation to cool air and costs very little to run. And the portable air conditioner, which uses a refrigerant circuit to genuinely bring the room temperature down and needs a duct out of a window. They both cool spaces. They both hire easily with next day delivery. They are emphatically not the same thing, and using one when you need the other is an experience that does not end with a cooler room.
This guide covers what each machine actually does, where it works well, where it does not, and which one HSS DIY recommends for different space types. It also covers the cost comparison, the setup, and the one question that determines everything: is the space ventilated or sealed?
At HSS DIY - The Home of Great Projects - both evaporative coolers and portable air conditioners are available to hire online 24/7 with next day delivery. Buy the materials. Hire the tools. One order. All in one place.
How Each Machine Actually Works
Evaporative Cooler - the water way
An evaporative cooler draws warm air over water-saturated honeycomb cooling pads. As the water evaporates, it absorbs heat from the air - the same principle that makes you feel cold when you step out of a swimming pool in a breeze. The cooled air is then pushed into the space by a fan. It adds a small amount of humidity to the air and works best where there is airflow through the space to allow the moisture-laden air to escape. In a ventilated workshop with the door open, or in a marquee, or in a warehouse with loading bay access, the cooling effect is real and measurable.
Portable Air Conditioner - the refrigerant way
A portable air conditioner uses a refrigerant circuit to extract heat from the room air and exhaust it outside via a duct. The process is the same one that powers a domestic fridge - compression and expansion of refrigerant gas. The room gets cooler because the heat has genuinely left the room through the duct. This works in a sealed space with no natural airflow, which is precisely where the evaporative cooler does not. The trade-off is higher energy use and the need for somewhere to route the exhaust duct.
Why Cooling Equipment Is No Longer an Optional Extra - The Climate Data
Hotter UK summers are not an anomaly anymore. They are the new pattern, and the data from the Met Office makes that very clear.
According to the metoffice.gov.uk - 2026 global temperature outlook , published in December 2025, 2026 is forecast to be the fourth consecutive year in which global average temperatures exceed 1.4°C above pre-industrial levels. The central estimate is 1.46°C - just below 2024's record of 1.55°C, which was the first year to temporarily breach the 1.5°C Paris Agreement threshold. Professor Adam Scaife of the Met Office noted that prior to this surge, global temperatures had not exceeded 1.3°C. The pace of change has accelerated significantly.
For anyone making a hire decision right now, the context is this: UK summers are trending hotter, and the Met Office data confirms that trend is accelerating rather than levelling off. The question of whether to hire an evaporative cooler or a portable air conditioner has become less about comfort and more about whether a space is going to be usable or productive through the summer months. Both machines exist to answer that question. This guide helps you pick the right one.
- More frequent heat events: extreme heat days that were historically rare are projected to become considerably more common across the UK as global temperatures rise
- Longer hot spells: extended periods of heat above 30°C in summer are expected to increase in both duration and frequency, affecting construction programmes, warehouses, offices and domestic living spaces alike
- Higher baseline temperatures: even average summer temperatures are trending upward, meaning spaces that were manageable in previous decades are now regularly exceeding comfortable or safe working limits
Source: Met Office - 2026 Outlook: Likely Another Year Above 1.4°C
For Home Workers and Domestic DIY Readers
If you are an employee working from home, your employer still has a duty of care under the Health and Safety at Work Act 1974. If your home office regularly exceeds comfortable working temperatures, providing cooling equipment is a reasonable and proportionate response. If you are self-employed, the NHS guidance recommends keeping occupied spaces below 26°C during hot weather - that is the practical standard for domestic settings.
The Decision That Changes Everything - Ventilated or Sealed?
The single question that determines which machine you need
- Ventilated space (open doors, windows, large airflow): evaporative cooler. More energy efficient, no exhaust duct, works outdoors, lower hire cost per week
- Sealed or enclosed space (bedroom, office, site cabin, server room): portable air conditioner. Requires exhaust duct, uses more energy, but the only machine that genuinely cools a sealed room
- Mixed building with both ventilated and sealed areas: use both. Evaporative cooler in the workshop or open area; portable AC in the office or sealed welfare room. This is covered in the case study below - it is a common scenario and a sensible solution
The HSS DIY Cooling Hire Range - Products for Both Technologies
Evaporative Cooler (Medium - up to 40m²)
Specs: Up to 40m² | 3 fan speeds | 60L tank | Wheels
Best for: Workshops, garages, smaller warehouses, DIY sheds with open access
Fan-assisted cooler using water evaporation over honeycomb cooling pads. Three fan speeds. 60L water tank. Ready to cool in minutes. Carbon dust filter prevents particles circulating. Wheels for repositioning. For optimum performance, use in well-ventilated, lower-humidity spaces. Not suitable for fully sealed rooms. Average hire from approx. £72
Industrial Evaporative Cooler (up to 150m²)
Specs: 380W | 8,000m³/hr | 60L tank | 7-day minimum hire
Best for: Factories, warehouses, large workshops, marquees and outdoor events
380W axial fan with three-blade impeller delivering 8,000m³/hr of cooled air. Covers spaces up to 150m². 60L tank - fill via hose for continuous use. Three speed settings. Carbon dust filter. Works on-site outdoors and in well-ventilated large spaces. 7-day minimum hire. Average hire approximately £96.
Hire Industrial Evaporative Cooler
Portable Air Conditioner (Compact 3.5kW - up to 25m²)
Specs: 3.5kW | Up to 25m² | 55dB | Wheeled | Exhaust duct included
Best for: Bedroom, home office, site cabin, sealed rooms up to 25m²
Refrigerant-based cooling for sealed spaces. Genuinely reduces room temperature by extracting warm air via exhaust duct. Quiet at 55dB - suitable for sleeping and working environments. Wheeled castors for repositioning between rooms. Exhaust duct and window seal kit included. From approximately £60.
Hire Compact Air Conditioner 3.5kW
Commercial Portable Air Conditioner (5kW+ - up to 40m²)
Specs: 5kW+ | Up to 40m² | 3m ducting | 360° directional outlets
Best for: Larger offices, meeting rooms, retail spaces, server rooms up to 40m²
For rooms too large for the compact 3.5kW. Three flexible directional cold air outlets with 360° swivel and 150° vertical adjustment. Spot cooler mode for directed cold air. 3m ducting included. General AC or spot cooling. Wheeled for repositioning. From approx £66.
Hire Commercial Air Conditioner
Cooling Fans (Office and Warehouse)
Specs: From compact office fan to 25,000m³/hr warehouse fan
Best for: Any space needing airflow - complements both evaporative coolers and portable AC
Cooling fans do not reduce air temperature but create airflow and wind-chill that significantly improves perceived comfort. The warehouse fan at 25,000m³/hr is the industrial scale option; portable office and commercial fans suit smaller spaces. Use alongside an evaporative cooler to distribute cooled air more efficiently, or independently for airflow-only applications. From £30.
Hire or Buy? The Summer Cooling Calculation
For a two or three week hot spell in a UK summer, hiring is almost always the right call. An evaporative cooler starts at around £100 to buy - a reasonable consideration if you use it every summer in a workshop. A portable air conditioner starts at around £250 for a basic domestic model. If you are going to use it for three or more weeks every summer, the buy calculation starts to make sense over a few seasons. For the majority of homeowners and most trade applications, hire wins on cost, storage and the ability to get a professional-grade machine for the duration.
Evaporative Cooler (medium, up to 40m²) | Hire: From approx. £72 | Buy: £100-£300+ | Verdict: Hire for a warm spell. Worth owning if you use it every summer.
Industrial Evaporative Cooler (up to 150m²) | Hire: From approx. £96 (7-day min) | Buy: £500-£1,500+ | Verdict: Hire. Used seasonally - ownership rarely justified.
Portable AC (compact 3.5kW, up to 25m²) | Hire: From approx. £60/week | Buy: £250-£600+ | Verdict: Hire for a heatwave. Buy if you use it every summer for 2+ months.
Commercial Portable AC (5kW+, up to 40m²) | Hire: From approx. £66 | Buy: £500-£1,200+ | Verdict: Hire. Overkill to own for 2-3 hot weeks per year.
Cooling Fan / Warehouse Fan | Hire: From approx. £30 | Buy: £80-£800+ | Verdict: Either - buy a domestic fan; hire for industrial-scale airflow.
Prices are estimates. Verify current rates at hss.com before budgeting.
⚠️ Safety and Practical Notes
- Exhaust duct is mandatory for portable AC: a portable air conditioner without a properly routed exhaust duct recirculates the warm air it extracts and heats the room rather than cooling it. The duct must exit through a window, ceiling void or suitable gap. Gap around the duct should be sealed to prevent warm air returning
- Evaporative cooler water hygiene: the water tank on an evaporative cooler should be filled with clean tap water and emptied if the machine is not used for more than 24 hours. Standing water in the tank can allow bacterial growth. Industrial and large models from HSS DIY include a carbon dust filter that also manages air quality
- Do not use evaporative coolers in fully sealed rooms: the humidity from continuous evaporative cooling can build up in sealed rooms. This is not dangerous but is uncomfortable - sweating in a damp room is not an improvement on sweating in a dry one. Evaporative coolers need ventilation to perform correctly and safely
- Extension cable rating for portable AC: portable air conditioners draw more current than most domestic appliances - typically 5-12 amps. Use only extension cables rated for the appliance load. Avoid daisy-chaining extension leads and check the cable is not coiled when the unit is running, as coiled cables under load can overheat
- Condensate tray on portable AC: most domestic portable AC units collect condensate in an internal tray that needs emptying - daily in humid conditions. A full tray causes the unit to shut off automatically. Check the product manual for your specific model
Which Cooling Hire Is Right for Your Space? The 5-Question Decision Guide
Q1 - Is the space sealed or ventilated?
Sealed room, no natural airflow: go to Q3 (portable AC).
Ventilated space with doors, windows or open sides: go to Q2
Q2 - Is it indoors or outdoors?
Outdoor or marquee: evaporative cooler. Open-sided indoor (warehouse, workshop, large shed):
evaporative cooler. Go to Q4
Q3 - Is there a window or ceiling void available for an exhaust duct?
Yes: portable air conditioner.
No: evaporative cooler with improved ventilation, or consult HSS DIY live chat for alternatives
Q4 - What is the space size?
Up to 40m²: medium evaporative cooler.
Up to 53m²: large evaporative cooler.
Up to 150m²: industrial evaporative cooler.
Smaller sealed rooms: compact 3.5kW portable AC.
Larger sealed rooms up to 40m²: 5kW+ commercial portable AC
Q5 - Is energy cost a factor?
Evaporative cooler uses roughly 380W (industrial model) - similar to a vacuum cleaner.
Portable AC typically uses 700W-1,500W.
For sustained summer-long use, the evaporative cooler running cost is significantly lower
Sealed or Ventilated. That Is the Question.
The evaporative vs portable AC decision is not complicated once you know which category your space falls into. Sealed rooms need the portable air conditioner and a window for the duct. Ventilated spaces - workshops, warehouses, garages with open doors, marquees - are exactly where the evaporative cooler thrives and the portable AC would be fighting a losing battle.
Both machines are available from HSS DIY with next day delivery. Both set up in under 30 minutes. And both make a genuine and immediate difference to a space that was previously best described as unworkable in July.
Pick the Right Machine. Feel the Difference by Tomorrow.
Browse the full cooling hire range - evaporative coolers, portable air conditioners, fans and industrial cooling - online 24/7 with next day delivery. Full cooling hire range
Buy the materials. Hire the tools. One order. All in one place.
Get DIY Happy.
Frequently Asked Questions
Does an evaporative cooler actually cool the air or just move it?
It genuinely cools the air - by passing it over water-saturated honeycomb pads, the process of evaporation removes heat from the air and reduces its temperature. The industrial evaporative cooler from HSS DIY produces 8,000m³/hr of cooled air. The key limitation is that this works best in ventilated spaces. In a sealed room where humidity is already high, the evaporation effect diminishes and the cooling performance drops. In an open workshop, garage or warehouse with airflow, the temperature reduction is real and significant.
Which is cheaper to run - an evaporative cooler or a portable air conditioner?
The evaporative cooler is significantly cheaper to run. The industrial model uses approximately 380W - comparable to a large fan. A standard domestic portable air conditioner typically uses 700W to 1,500W. Over a sustained summer programme, the difference in running cost is meaningful. The trade-off is that the evaporative cooler needs water (8-10 litres per hour for the industrial model on continuous use) and works best in ventilated rather than sealed spaces. For a sealed office or bedroom, you need the portable AC - but in a ventilated workspace, the evaporative cooler is the more cost-effective choice.
Can I use an evaporative cooler indoors?
Yes, with the right conditions. Evaporative coolers work best indoors in spaces with natural ventilation - a workshop with an open roller door, a warehouse with loading bay access, a garage with the door open. They should not be used as the primary cooling solution in fully sealed rooms because the humidity builds up and the evaporation process becomes less effective as the air becomes saturated. For a fully sealed room with no natural airflow, a portable air conditioner with an exhaust duct is the correct hire.
What size evaporative cooler or portable AC do I need?
It depends on the space size. For evaporative coolers: the medium model covers up to 40m², the large model up to 53m², and the industrial model up to 150m². For portable AC: the compact 3.5kW covers up to 25m², and the 5kW+ commercial model covers up to 40m². For south-facing rooms or spaces with significant heat sources, increase capacity by 10-15%. If in doubt, the HSS DIY cooling calculator on the air conditioning category page helps you calculate required cooling capacity.
Can I hire both an evaporative cooler and a portable air conditioner at the same time?
Yes - and for mixed-use buildings this is often the right approach. A workshop or warehouse runs well with an evaporative cooler; the office or welfare area inside the same building benefits from a portable AC. You can add both to the same HSS DIY hire order. This is exactly the scenario covered in the case study in this article. One booking, two different technologies for two different space types.
What is the difference between portable air conditioner hire and portable air conditioner rental?
Nothing - they are the same thing. Hire and rental both describe short-term use of equipment for a daily, weekly or longer fee. HSS DIY uses the term hire, but if you search for portable air conditioner rental you will find the same range and the same service. The key features are next day delivery, flexible hire periods, and the option to return the unit when the weather breaks rather than storing it for eleven months of the year.
Useful External Sources
NHS - Heatwave: How to Cope in Hot Weather: nhs.uk/live-well/seasonal-health/heatwave-how-to-cope-in-hot-weather - NHS guidance on keeping cool during hot weather, including recommended indoor temperature ranges for health
Energy Saving Trust - Cooling Your Home Efficiently: energysavingtrust.org.uk/advice/cooling-your-home - Practical guidance on the most energy-efficient ways to cool different types of domestic and commercial spaces
Met Office - UK Heatwave Advice: metoffice.gov.uk/weather/warnings-and-advice/seasonal-advice/heatwave - Heatwave warnings and seasonal advice for the UK. Sign up for alerts to book cooling hire before demand peaks
HSS DIY YouTube: youtube.com/@HSSDIY - Equipment guides from The Home of Great Projects
Prices shown are indicative hire and buy rates as of 15 May 2026 and subject to change. Always check hss.com for current pricing. HSS ProService Ltd.
