I have a 10 x 12 greenhouse and living in the north of Scotland, frosts can be a problem. I usually start my tenders off in April and are frost free by early May. That leaves four weeks for potential disaster.
Enter the greenhouse heater.
This model has 2 burners and each burner has two independently controlled wicks.
These allow you alter the height of the flame and which flames you have on.
I have tried various combinations and I find that unless the temperature is going to be really severe, one wick in either chimney keeps me frost free on a moderate flame (not too big or smokey).
Filling the can is easy. A lid screws off and you fill. To keep the can clean I would recommend the use of a funnel.
To light the wicks the chimneys are removed (easy) and put back on when lit. I would recommend leather gloves when putting the chimney on when the burners are lit and removing the chimney top in the morning. The wicks can be blown out.
A 4L can of paraffin lasts upto 2 weeks depending on the severity of the
weather.
If want to start your tenders early or keep your tenders frost free, then this comes very highly recommended. Easy to use and economical.