Do I Need a Bigger Air-Con To Cope With a Gaming Computer?

We have evaporative cooling on the second story of our house in Melbourne. However, my daughter’s bedroom is on the ground floor and she has an illness that makes her ultra-sensitive to temperature so, we are looking at a small split system for her bedroom on the south side of the house. The room is 23 m square & has approx 2.5 m high ceilings. One article I read on Choice stated that in Melbourne you would only need about 2.3 kW of cooling for a 30 sq m room. Elsewhere they say you need approx 2.5 kW for a 20 sq m room. Then, there is the fact that my daughter has a gaming computer that generates approx 300 - 400 W of heat. The house is 4 years old 6 star energy rated with double glazed windows.

Would a 2.5 kW unit be sufficient?





Being on the Sth side will reduce significantly the heat transmitted through the walls as it is shaded from the sun (assuming it isn’t the Sth West room and thus might get the afternoon sun heating), the ceiling heat load will depend on the insulation you have or haven’t got, and any shading of the walls and roof that exist. Add in the heat generated by the computer (and how often and when it is running) and that might give you a better idea of the capacity needed.

Cycling rather than full time on cooling is important. The AC should be big enough but not too big to cool the room down to the selected temp then cycle off (just circulating the air mostly…cooling is at a very low level) until the temp rises enough to start more active cooling again. Erring on the side of a little more cooling capacity is probably a good idea if you don’t get a professional assessment of needed capacity.


Welcome to the community @brettsh,

The computer is probably noise in the equation excepting your daughters susceptibility to temperature variations. I presume you mean it has a 400W power supply, that is on the modest side as power supplies go? Under full chat maybe a bit of warm (not hot) air blowing out, but shouldn’t be concerning for the room.

I presume you mean 23sqm? It turns out I have a similarly sized bedroom facing south with a large single pane aluminium framed window.

I installed a 3.5KW Daikin last year, sized on recommendation. Based on my experience a 2.5KW might do it, but you will probably be happier with the headroom of a 3.5 and the cost differential should be minimal.


The cost of installing a small size split aircon including the electrics is often greater than the purchase cost of the air con. Being too small or overloaded, it is expensive to remedy.

The latest quality inverter models are more efficient. Whether the last few cents of running cost are a concern, we made the call to ensure that the new MHI inverter air cons we purchased were on the up side of what the room calculator said. They adjust to the load really well. We also sized for modest cooling and heating outcomes. 26C inside in summer vs 36C high humidity outside and 18-20C warming vs 10C outside in winter. Personal comfort may also be a factor in what you decide. We have also positive experiences with Fujitsu and Daikin brands. Best to read the reviews.

Choice has a guide and product reviews if you have not read them recently:


One of my computers has a 800 watt power supply, that produces a reasonable amount of heat dropping the voltages down, then there is my graphics card, and the CPU and all the board electronics…it produces significant heat loads to the room it is in. A 500 watt supply in itself probably not so much a worry but add the other components in and in the circumstances an under-powered AC will further struggle to cope. I agree a slightly more higher capacity unit is warranted.


Old fashioned cycling can be a furphy. Systems go full on to cool down the furniture and walls, but once cool most modern units don’t use much power to stay cool and the difference in comfort level can be huge.

My expectation is what you are describing as cycling is normal A/C operation where the compressors are controlled to maintain a set temperature +/- . Are there any that do not these days where inverter technology is the norm?

Excellent affirmation :slight_smile:

more than one…


I am lost. If you have an 800W power supply, doesn’t it power the graphics card and everything else in the chassis? 800W heat load full chat?

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Wow, quick responses. Thank you guys :grinning:

Yes, I did mean 23 sq m sorry.

Yep, I’ve read the reviews. I’ve been a member of Choice for years, the subscription is worth every cent.

I was rather taken by the MHI srk25zsxa-w, an extremely efficient 2.5 kW unit. However, I’m beginning to think a 3.5 kW unit is not too large for the room. As you say, the purchase differential won’t be that much.

Thanks again




Yes and inverters can do a great job of maintaining that with modest power usage. But if a room has an under capacity unit the inverter can be as bad as running an old style unit at 100% all the time. This ends up just being a situation of power over use and cooling under performance. Over capacity can be as bad as the old cycling issue.

From a professional AC site:

"An inverter air conditioning unit is perfect for linear temperature control but there are limitations. If the air conditioning unit is undersized for the area the inverter compressor will then operate at a high speed level which in affect works comparably with a fixed speed compressor working at 100% capacity, thus using more power. The flip side to this is, if the inverter air conditioning compressor unit is oversized for the area the unit will not be able to operate within its designated range. Inverter air conditioning units have a working range for their capacity which usually starts at a minimum of 1.0kW on small models. Below is a common operating range of capacities for inverter air conditioning listed by the main manufactures Mitsubishi and Daikin air conditioning:

Typical Inverter Air Conditioning Operating Ranges:

2.5kW / 9000Btu Inverter air Conditioning units (0.9kW to 2.5kW)

3.5kW / 12000Btu Inverter air Conditioning units (0.9kW to 3.7kW)

5.0kW / 17000Btu Inverter air Conditioning units (1.3kW to 5.4kW)

7.0kW / 24000Btu Inverter air Conditioning units (1.9kW to 8.23kW)"

and their final considerations on sizing

" Key Considerations When Sizing Up Inverter Air Conditioning:

Do not oversize the air conditioning unit as it will end up switching off and on like a old fixed speed compressor

Do not undersize a inverter air conditioning unit as it will run at full speed like a fixed speed compressor

Look at the operating range when sizing up your area

Try to match the capacity to the room size to the nearest 500 Watts"

Why I recommend a professional assessment of the need (and as you stated perhaps more than one).


Oh thanks, the operating ranges make a lot of sense :grinning:

Yes, I’m beginning to think that a professional assessment is a good idea. There are several variables to consider.


No the PS has heat from just converting AC to DC whatever it’s capacity to power internal computer components is and that heat can be a bit… Then each component is not perfect in usage, there are heating issues across the board, so add in that so for a 500 Watt unit you could produce from the PC roughly 500 watts of heat plus the added conversion the PS does to produce that 500 watts of DC… That is why some add external power support to the cooling they provide for their machines as the PS cannot provide sufficient (even with 1.2 kW or bigger supply). The fact they have such huge supplies is sometimes mind boggling to me unless they are mining currency with multiple graphic cards. The more efficient PSes are now rated eg 80 plus Gold, 80 plus Bronze etc meaning they can supply the rated power at a “certified” percentage,36721.html


My last ‘real computer’ goes back to 2009 - more accurately my agency’s - only pulled in 1 MW plus another 500 KW for the peripherals. The cooling system was pretty special. The computer was modest among its peers. At the time a ‘proper real computer’ used 3 MW. If you get to visit the Australian Synchrotron it uses 3 MW and the wiring loom is on top, easily visible, and impressive!

Back to topic, without regard to efficiency factors and conversion losses in ratings I try to keep it simple that a 500 W rated power supply does 500 W. Unless someone mentions it, I default to systems that are comparatively simple and not water cooled nor do they have graphics cards that use more power than the CPU and motherboard bits.


Only 1 MW? Many years ago I used to work on a mainframe system that generated 2 KW of heat and I thought that was bad :upside_down_face:

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Did you drop some 0’s? Maybe 20 or 200 KW, era dependent? A modest minicomputer in the 1960’s drew 1,200W.

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You’re right, that was probably a fraction of the overall consumption. It was a Modcomp Bailey 1055, late 70’s technology. I remember the CPU cabinet was supposed to generate about 2kW. There were several other cabinets in the computer room for interface stuff and the consoles were located in another room.


Apologies. I would not have called a Modcomp a mainframe. Modcomp was a very nice minicomputer that essentially ‘owned’ much of the SCADA market in its time. 2KW +/- may well be the right order of magnitude.

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As has been implied, a power supply with a rating of X Watts doesn’t necessarily consume and dissipate X Watts. It depends on your actual PC configuration and your use. The best way of dealing with that is to measure it (on the AC side i.e. before the PSU). A power meter can be had for not much money these days (assuming you only need 10A, which should apply to random ‘gaming’ computers even if not to gas guzzling mainframes).

Don’t forget the monitor(s). Not much point having a zillion Watt gaming computer unless you have a decent monitor/s to go with it - so that’s some more Watts to consume and dissipate.


I recently installed a Mitsubishi Heavy Industries Inverter 3.5 KW cool 3.8 KW heat split system to cool and heat a similar sized area . I was advised a 2.5 KW cool would suffice but am really glad I took the advice of a friend in the industry and went for the more powerful unit .


IMHO it’d be prudent to get three or more professional assessments, as suggested, but stress the primary issue is to keep the temp constant given your daughter’s needs. In other words ask them to solve the problem rather than focussing on capacity. This isn’t a conventional aircon problem so for example it may be better to have a smaller unit that works more often and changes temp more slowly rather than a large unit that makes the temp fluctuate quickly so it’s probably a combo of capacity and sensor activity and will need some thinking outside the box. It might be worth talking to the aircon tech folks at the brand headquarters in Australia rather than retailers as they can sometimes give you detail that retailers won’t have or don’t care about, and also reaching out to any professional bodies or forums that have knowledge of your daughter’s situation as they can sometimes be a great resource.


Thanks Mustang. You make an excellent point about the primary issue being the need to keep the temperature constant. I’ve fired off an email to MHI and will get professional assessments.

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