They Are Ways of being eco-friendlier than low power vacuums
Starlightsam - a very good point and I see where you're coming from. However, therein lies the possible factor that a higher powered vacuum will lift far more dust in a shorter time than a low powered vacuum OR dependent on the type used at the time with the same consideration for the type of floor head etc you intend to use.
But what happens if you use a kettle 5 to 10 times a day to make endless cups of tea or coffee - particularly if you like your water to be hot to drink? Counter in the amount of times you use a small appliance like a high energy kettle a day and a high power vacuum cleaner can be used in the same amount of time it takes to boil as many mugs of tea or 1 litre of water. This is where I'm afraid, the question of so-called "Eco" kettles are a full of false promises - if the rating plate reads 3000 watts, it isn't eco friendly, no matter how much you fill the water level up to, even if smaller amounts need less power to boil, they're still using that 3000 watts the moment it is switched on - what buyers don't realise is that they can buy the cheaper 2200 watt kettle but at the expense of less convenient features (a bit like bagged uprights on the market today where features that were once present have now been taken out) such as concealed elements or rotational bases.
My theories surround the amount of energy that is wasted by powering up appliances in the first instance - from dishwashers to tumble dryers, to washing machines and the appliances that are constantly left on like the fridge freezer. Eco branded appliances are not eco-friendly in my experience (see previous thread with my experience of my Bosch dishwasher as a classic example - the Eco setting takes a far longer wash time than the three other programs).
My daily appliances such as the microwave oven is switched off at the wall. I don't take delight in programming the digital clock knowing that the oven is effectively on standby mode, still plugged in and still supplying that small quota of energy before it is actually used.
To some of the younger members on here where mummy or daddy pay the bills in your home, then you don't have to worry your head about energy costs.
However my parents are both deceased and I pay all my own bills being a single adult; i often find myself vacuuming in the early hours as that's when my power goes on half rate! During the day if I need to do a quick clean, the cordless Gtech gets taken out.
The cost of central heating is so high that my heating only goes on three days a week and my parents house of which I inherited has an old boiler system with radiators that can't be switched off individually. Thus I have to use portable convector "pipe" radiators (they're a new range from Dimplex called Eco radiators) just to heat the room I'm in rather than heat up the whole house and waste the energy in rooms I'm not using. Eventually once I've saved up a bit, I'll be installing much better boiler system, but by then I also intend to move out of Scotland once and for all, too.
But then you know what its like if you're a collector. Sometimes for that bit of luxury you can't help but use a vacuum cleaner just for the fun and sheer enjoyment of it..during the day.
Even if brands begin to launch vacuums with lower motors, they still need to address sealed suction and airflow. Some brands are worse than others for this, even for those who produce bagged vacuums.
Interestingly, Alex - can you determine what you mean "decent" from your first post, please? It is nigh difficult to know what you mean, otherwise.