Aircon Myths Busted: Does Leaving it on All Day Save Energy?

Aircon Myths Busted: Does Leaving it on All Day Save Energy? It is one of the most debated topics in the world of home cooling: Should you leave your air conditioning running all day at a steady temperature, or is it cheaper to turn it off when you leave and blast it when you return?

In the UK, where we are increasingly conscious of energy prices, getting the answer right can save you a significant amount on your monthly bills. At OJ Gas & Heating, we’re here to separate the “thermostat myths” from the scientific facts.

The Myth: “Starting Up Uses More Energy Than Running All Day”

The logic behind this myth is that your aircon has to work “extra hard” to cool down a hot room, consuming a massive surge of electricity. People often compare it to a car using more fuel to accelerate than to cruise.

The Reality

While your AC does work harder during the initial cooldown, it is almost always more energy-efficient to turn the unit off if you are going to be out for several hours.

Think of it this way: heat is constantly leaking into your home through walls, windows, and doors. If the AC is on all day, it is fighting a never-ending battle against that incoming heat. If the AC is off, you stop paying to fight that battle until you actually need the comfort.

The “Inverter” Exception

The answer changes slightly depending on the type of technology inside your unit. Most modern systems installed by OJ Gas & Heating use Inverter Technology.

Older Units (Non-Inverter): These are either “all or nothing.” They blast at 100% power until the temperature is reached, then shut off. These are very expensive to leave on all day.

Modern Units (Inverter): These are like a dimmer switch. They can slow down to a very low power mode (e.g., 10% capacity) to maintain a temperature. If you are only popping out for 30 minutes, an inverter unit is efficient enough that you might as well leave it on. If you’re out for a full workday, turn it off.

3 Better Ways to Save Energy

If you want to keep your home cool without the “all-day” electricity drain, try these expert tips:

1. The “Pre-Cool” Strategy

Instead of leaving the AC on all day, turn it on 20 minutes before you get home using a smartphone app or a timer. This way, the house is cool when you walk in, but you haven’t paid to cool an empty building for eight hours.

2. Close the Internal Doors

Air conditioning units are usually sized for a specific room. If you leave the bedroom AC on but keep the door open, the unit will try to cool the hallway and the stairs too. This keeps the compressor running at max power for longer, driving up your bill.

3. Use a Higher Set Point

If you absolutely must leave the AC on (perhaps for a pet), don’t leave it at 19°C. Set it to 25°C. This keeps the edge off the heat and protects your pets, but ensures the unit stays in its lowest power-consumption mode.