I want to heat a largish room (about 8m x 3.5m) with an oil filled radiator. i want to get the balance right between energy efficiency and a large enough wattage to emit lots of heat.; can anyone recommend a rad or even a wattage or brand to give me a starting point? many thanks!
All electric radiators are 100% efficient at converting electricity into heat. There's just nothing else the electricity can do in a radiator than turn into heat. So you don't need to look very far, any oil filled electric radiator heater will give you the efficiency you're after.
Remember though that the heater is using electricity, which if generated from coal, oil, or natural gas, means that only about 30% of the original energy in the fuel gets converted into heat in your home, because 'heat engines' (such as the turbines in power plants) are rarely more than 35% efficient, and there are also transmission losses getting the heat to you.
Look for a heater with a higher wattage given the room size you have. And be prepared to pay a lot to heat the room – the bigger the wattage of the heater, the more electricity you'll use.