It's getting colder and time to get out the heaters! But if you are buying a heater, here's a few tips when listening to the salesman.
All heaters (except for heat pumps which don't actually convert electricity to heat) are 100% efficient. If a salesman tells you one 2000W heater is cheaper to run than another 2000W heater, they are either lying or don't know what they're talking about. It's like saying one 2L bottle of milk has more milk than the other 2L bottle of milk. The thing you need to base your decision on is what style of heating you want. Fan heaters heat the air in the room more quickly, but the air is then cooled by the floor, walls and ceiling. Convection heaters take more time to heat the air, but at the same time the heated air slowly heats the walls, ceiling. Radiators, like panel heaters and oil heaters take even longer, but they are a more consistent heat since they heat the walls, ceiling etc which in turn evenly distributes the heat throughout the room. Once the room is heated, the ambient temp is easily maintained.
So if you're icy cold and want instant heat, sit in front of a bar heater or fan heater. If you want the room to be comfortable, switch on a convection or panel heater about 20 minutes before you want to use the room (depending on how cold the room is, you may need to give it longer). The more you spend on a heater with a thermostat, the more consistent the ambient temperature.
If you have a heat pump, turning up the temperature doesn't heat the room more quickly. Just set it to the temperature you find comfortable and wait for it to bring the room to that temp. Setting it at a much higher temperature takes the same amount of time to heat the room, but then it keeps on raising the temp until it reaches the dialled temp. Keep curtains closed and keep doors closed that will allow heat to escape, like bathroom, hallway, toilet, laundry doors etc.
Don't heat parts of the house that you seldom use, such as toilet, spare bedroom, etc. Keep those doors closed. Try to localise the heat to where it's needed most. Unless you plan to spend the evening sitting in your hallway, keep the doors closed and retain the heat in your living area.
The most efficient form of heating is the heat pump. Spending a couple of thousand dollars on a heat pump will pay for itself within a few years and you also gain the added benefit of cooling in the hot summer. If you don't want to have a fixed heat pump installed, you can always purchase a portable heat pump (portable air conditioner) for a fraction of the cost. Generally you'll find these portable heat pumps are rated at around 1kw power consumption and they will produce around 3kw of heat. That's like having three 1kw heaters for the price of one!
So at the end of the day, when the salesperson says to you, "This heater is more efficient to run that that heater," what he's actually saying is either a. "I don't know what I'm talking about" or b. "This heater is a lower wattage and will produce less heat than that heater."