Because air conditioners are not cheap as chips, the question of how long they last is a pertinent one. However, 'air conditioners' is a word like 'shoes' - because there are a lot of different kinds! There's ducted, split systems, portable air conditioners and many more. But for most quality systems made by reputable manufacturers, the average warranty length is somewhere in the region to 12-15 years - which is a clear indication of predicted longevity.

Realistically, though - and especially if you follow the manufacturers' maintenance schedules strictly - you can expect to get up to 25 years or more from your new unit. To boost your chances of an air conditioner that lasts a quarter of a century or more, get it installed and serviced only by highly reputable and fully licensed air conditioner technicians.

Also relevant for air conditioner longevity are:

• Thermostat settings/general usage
• Climactic conditions and weather exposure (especially humidity, heat & rain)
• Air quality (ie. salty seaside locations).

The short answer is yes - from a legal, safety, warranty-related and investment point-of-view, you definitely need a fully licensed electrician to carry out professional installation and all servicing and repairs on your air conditioner unit.

It's important to note, however, that while electricians possess the basic skills and credentials to get the job done, specialist air conditioner technicians have the hands-on experience, deep technological knowledge and most specialised equipment & tools for true consumer peace of mind.

More generalised electrical appliance professionals are less experienced with dangerous refrigerants and may lack licensing by the Australian Refrigeration Council and the associated accredited training.

It may feel refreshing on a hot day, but that perfectly cooled air definitely isn't cheap. How much it costs per hour, however, depends almost entirely on the air conditioner type, as there are vast running cost differences across the vast technological range.

What is clear is that, for most Australians, cooling and heating the air accounts for about 40% of homeowner's energy costs - and even more for those who are heavy users of ducted reverse cycle systems. More generally, the cost per hour depends on factors including:

• Wattage
• Energy star rating
• Fan/system speed
• Size/characteristics of home/rooms.

For guidance, cooling a small space with a small, efficient air conditioner can be as little as 25 cents per hour, rising to well beyond $3/hour for the aforementioned hefty reverse cycle unit in a bigger home.

With weekly household budgets more stretched than ever, it's tempting to wonder if you can save a few dollars by repairing your own air conditioner. If the 'repairs' involve cleaning or even replacing filters, or maintenance tasks like keeping the area clean & clear around the external unit, the answer is probably 'yes' - you can do some air conditioner repair DIY.

However, it's important not to overstep the mark and damage your system, incur much larger professional repair costs, or even terminally damage your air conditioner whilst simultaneously voiding the warranty. Before considering DIY air conditioner repair, consider:

• Safety: Remember, air conditioners consume high voltage levels.
• Tools: Not using specialised tools could only damage your system even more.
• Incorrect diagnosis: All too often, amateur diagnoses of problems can only exacerbate the real source of the fault.

Air conditioners aren't just expensive upfront, the ongoing costs are significant too - and then, servicing and repairs can cost you as well! It's therefore good to be ready for the most common problems when they crop up.

The most common problem, perhaps unsurprisingly, is that when you press the 'on' button, it simply doesn't turn on. Sometimes, the solution is super-simple - like a new set of thermostat batteries. It could also be another minor problem like a tripped circuit breaker.

The next most common air conditioner problems are:

• Dirty air filters
• Blower/motor issues
• Refrigerant leak
• Damaged compressor
• Electrical control problem
• Blocked drain pipe/other drainage issues
• Sensor failure.

While you should always rely on the fully licensed and experienced services of a professional air conditioner technician, many common problems can actually be diagnosed by the homeowner.

So if you're having an issue with your system, follow these troubleshooting steps to get a head-start as to what the solution might be:

• Is the air filter dirty?
• Is the thermostat set correctly?
• Are the thermostat batteries flat?
• Are the circuit breakers tripped?
• Have you visually inspected the outdoor unit?
• Have you checked the air vents?

We would have also listed 'Are your refrigerant levels too low?', but certain critical issues such as this can only be attended to by a qualified HVAC electrician/technician with specialised tools and experience.