Working from home in the heat wrecks your focus: above 27-28 °C you think more slowly, sweat and make mistakes. The office or work corner then becomes the room to cool first, often all day long. But an office has its own demands: quiet for video calls, appliances that give off heat, long hours of use. This guide covers how to cool it well without breaking the bank or deafening yourself.
The right power for an office
A home office is often 8-15 m². By the ~340 BTU per m² rule, a 7,000-9,000 BTU unit (2.0-2.6 kW) covers most cases. But an office holds heat sources people forget: computer, monitors, printer, router. Allow a little headroom for that internal load.
If the office gets afternoon sun or sits in a loft, add 10-20%. Conversely, do not over-size a small room: a unit that is too powerful will switch on and off constantly, which is also the most distracting thing for concentration.
Quiet, essential for video calls
In an office, noise is not just a comfort issue: a monobloc at 55 dB(A) is heard on every video call and wears on you over the hours. The mic picks it up, the people on the call notice, and you end up switching it off for meetings — so back to working in the heat.
A split-type portable such as the Midea PortaSplit sits around 39 dB(A) because the compressor is outside the room. At that level it goes unnoticed on a call and lets you work cool without cutting the cooling every time the phone rings. For daily professional use, this factor weighs heavily.
The running cost of continuous daytime use
An office is often cooled for eight hours straight, which changes the sum compared with evening use. A 3.5 kW unit draws 1.0-1.3 kW; eight hours a day works out at roughly £1.80-£2.90 a day at about 28p per kWh, depending on how the inverter modulates.
- Set the target at 25-26 °C: enough to stay sharp without over-using power.
- Draw blinds and curtains on the sunny side before midday.
- Switch off appliances you are not using: every lit screen heats the room.
- Close the office door to concentrate the cold on the one useful volume.
- An inverter model with a good energy rating smooths the cost over these long days.
Special case: sensitive kit and a 'server corner'
Some home workers keep a small rack, a NAS or a compute box that runs hot and needs to stay cool continuously. There the priority is no longer human comfort but a stable temperature, including when nobody is in the room.
A portable can help, but aim for a programmable model that holds a set temperature, and watch the condensate in prolonged use. For genuinely critical kit a portable is a stop-gap: size it generously and keep an eye on the water-tank safety cut-out so it does not shut down unnoticed.
Frequently asked questions
What power do I need to cool a home office?+
For an 8-15 m² office, allow 7,000-9,000 BTU (2.0-2.6 kW) by the ~340 BTU per m² rule. Add a little headroom for the computers and monitors that give off heat, and 10-20% if the room gets sun or sits in a loft.
Which portable AC is quietest for video calls?+
A split-type portable, whose compressor sits outside the room: it runs around 39 dB(A), versus 50-65 dB(A) for most monoblocs. At that level the mic does not pick it up in a meeting and you do not have to cut the cooling every time you take a call.
How much does it cost to run a portable AC all day?+
A 3.5 kW unit run for eight hours works out at roughly £1.80-£2.90 a day at about 28p per kWh, depending on how the inverter modulates. Setting the target to 25-26 °C and closing the office door cuts that noticeably over a season.
Can a portable AC cool a small server room?+
As a stop-gap, yes, provided you pick a programmable model that holds a set temperature and you watch the condensate in prolonged use. For genuinely critical kit, size it generously and treat the portable as a backup rather than a permanent solution.
Should I switch the AC off when I leave the office?+
For a short break, no: letting it hold the set temperature costs less than cooling the room from scratch on your return. For a long absence, switch it off or set a timer. Never leave it running flat out in an empty room all afternoon.
Read also
- Quiet portable air conditionerWhat dB(A) to look for, and why design beats any night mode
- What BTU do I need for my room sizeWork out the exact BTU for your room without going under or over
- Portable air conditioner running costsWhat it really costs to run, and how to read the label to pay less
- Cooling a bedroom in a heatwaveThe full bedroom set-up for getting through hot nights cool
Know what you want? Find it in stock
We track the Midea PortaSplit's availability in real time across the UK retailers that actually sell it. Check the stock radar or set an alert and we'll email you the moment it's back.
Get alerts · From £4.90