How Does Car A/C Impact The Fuel Consumption?

In a tropical Country and developing country like India, ACs are no longer an optional, but mandatory feature in cars. It not only keeps the interior cool and cozy, keeping the window closed also prevents entry of dusts inside the car. Unlike Home ACs, car ACs run on rotational mechanical power and not on electrical Power. This power is drawn from the Engine itself, thus eating into the fuel efficiency, as a percentage of power generated by the fuel combustion is used in running the AC compressor instead of the wheels. In short, if you can run 16km in 1 liter fuel without AC, with the AC on, you will require more than 1 liter to run 16km.

A simple DIY observation (If your car comes with an rpm-meter).

1. Start the vehicle with your AC off, and wait for a while at idle (few seconds for petrol, about a minute for diesel).
2. Note the rpm (rotations per minute) reading. Should be around 650-1000.
3. Switch On the AC, and you can notice an instant increase in the rpm by about 100-150 units. This is because now more power is demanded from the Engine because the compressor is required to be driven.

One of the primary aim of Auto Manufacturers had always been, increasing of the fuel efficiency i.e. decreasing of the fuel consumption, and this is very much evident from their marketing banners, where the Kmpl. (kilometer per liter) consumes quite high amount of real estate. To supplement this objective, car ACs have had undergone some changes over the years. Though the AC compressor still draws power from the Engine itself, a lot of electronic controls accompanied by sensors, are being used to provide as optimum performance as possible.

The AC compressor has a pulley, which is driven by a belt and powered at the other end by the engine. A clutch is used to engage and disengage the pulley from the compressor. The power consumed by the compressor depends on the load on the compressor. There are certain situations when the compressor clutch is disengaged and the compressor stops working; as in, when the interior temperature becomes too cold or the compressor discharge pressure becomes too high.

It is a noticeable fact that with AC on, in a jam-packed city like Mumbai, you are likely to receive lower fuel average from your car. This is because most of the times the car either stays on idle, or moves in the first or second gear. All the while excess power is being utilized by the AC, whereas the wheels are not rotating at their full-fledged vigor. So, low kilometer (km) run and more fuel (l) utilized, results in lower kmpl or more commonly known as fuel-average. So if your car is providing low kmpl in cities, then probably its inevitable and your car doesn’t require an AC repair yet.

In lower end cars, there can be a noticeable drop in pick up when the AC is switched on, compared to windows-down. It is pretty normal, and no worries there. But if it drops by a substantial amount and along with it, if you are receiving really poor average from your car, it is time to consult a car workshop. Also, if the AC is not providing you enough cold air, again, it is time to get the AC serviced.

For convenience, you can log on to www.carworkz.com and search for the most suitable workshop near you by entering AC service or AC repair as job requirement. This website and app based platform helps you to check the features of a workshop, and enables you to filter workshops by type and compare their features. The platform also enables you to book an appointment online and track real time progress of your car servicing. Also it has a Service cost estimator to provide you an estimate for the service and carworkz-assist to help you in case of emergency breakdowns.