I am hoping someone with far more knowledge and experience than me can help with this one. I fitted two Stelrad radiators in my living room well over 20 years ago, and now want to replace/upgrade them. But I do not know the heat output. I have contacted Stelrad but they say they cannot help, and I threw out the data sheet years ago! They are 12 inch (30cm) high x 57 inch (145cm) long single panel unfinned. How many BTU's (or Watts for those who prefer), that is the question? Any help or advice would be much appreciated. regards, boydell.