Earth Hour may be the most gratuitous environmental free kick ever paid to corporate Australia.

Signing up is easy. Fill out your company details online and voila, you’re one of the more than 18,000 companies, from corner stores to corporations, who will plunge themselves into semi-darkness for an hour on Saturday night, all for the sake of the planet. More than 2,000 companies have joined since yesterday alone.

Now that you’re raising awareness about energy consumption, what are your responsibilities? Well, that’s for you to decide. It’s a bit like APEC’s Sydney Declaration on climate change in that regard. It won’t hurt a bit.

But if you’re looking for some ideas, here’s what some of Australia’s marquee businesses are doing for Earth Hour.

McDonald’s outlets will turn off their golden arches for an hour. Without those beacons lighting a safe path to nourishment, there will be hunger. But if you somehow find your way in the gloom, nary a nugget will go unfried. Nor will the fleet of distribution trucks pull to the roadside. Though in fairness, you will read more about saving the planet on the specially printed tray-mats.

Bob Gardiner, leader of the Australian sustainability program at Pepsico, told Crikey that his organisation would “make sure that the lights and everything else is turned off. But it’s a bit late to do much else. We only signed on a couple of months ago.”

Hewlett Packard told Crikey that concern for the environment “is in its corporate DNA. We are turning off all of our lights in office buildings all around Australia, and where we have the power to do, any outside illuminated signage.” At 8pm. On a Saturday night. It raises the question of why this isn’t standard operation procedure for all Australian businesses. At 8pm. On a Saturday.

BP Australia will also turn off all non-essential lighting, though there’s not much of that on a petroleum refinery. Spokesperson Chandran Vigneswaran told Crikey that BP’s 300 owned and operated service stations would be turning off their streetside signage, before adding that Earth Hour isn’t seen as an environment cure-all at BP, rather a part of its broader commitment to the environment.

James Hardie is taking Earth Hour in its stride, with staff being urged to turn off office equipment when they leave work on Friday. Does the company see Earth Hour as a cost-free way to garner some green love from consumers? “No, we don’t think it’s an easy free kick at all. It’s something we were asked to participate in and we said yes.”

Although the South Australian Police force has joined Earth Hour, local crims won’t find the going any easier on Saturday night. In fact, the SA Police are so focussed on maintaining law and order during the event, a senior media advisor revealed to Crikey that she didn’t know what Earth Hour was. Once Crikey explained the concept, she admitted to having heard something about it from her daughter. A call back later confirmed that SA Police would be turning off unnecessary lighting and appliances “where it wouldn’t endanger public safety”.

Earth Hour sponsor Channel Nine won’t be urging viewers to switch off their TVs for an hour, though it appears someone in programming is sympathetic to the cause. Both Sydney and Melbourne get the Bridget Fonda-vehicle Snow Queen from 8.30pm — a stronger argument for saving electricity is hard to find.

But this is only the tip of the slowly melting iceberg. According to yesterday’s SMH, 92 of the ASX 100 companies will observe Earth Hour. What’s surprising about those numbers is that there are eight companies foregoing the greenie points. Someone’s going to cop it on Monday.