Claims oil free is 30% faster warm up, and uses 9% less energy. https://www.amazon.co.uk/dp/B002DGTMJE
Not as cheap, but they do work well. It has a few bad reviews, but they include such gems as 'I bought this as a travel heater to put in my suitcase, and it's too big'. A couple of people burned theirs out by leaving it set to maximum for many hours. And a couple carelessly broke the on off switch. I have three and never had an issue. They are suitable for a bit of extra warmth in a smallish room, not heating a big cold room. Put it this way, I have mine on a Tapo plug, set to 15 minutes. So obviously, 15 minutes is often all I need. And set to about 33%, it generally turns itself off before then anyway, with the thermostat. Typiclly, if left on without the Tapo, it would run for about 7 minutes, three times an hour.