Thank you for your question.
The range stated on the Saltfire ST1 stove is like the min - max heating on an electric fire. With a small amount of fuel the ST1 with operate at 2kW but with a full load of seasoned hard wood logs it will produce much more heat equivalent to 5kW.
Some stove manufacturers list a heat output range and some just list a maximum output.
I notice you're asking all the right questions, have you used our stove calculator yet to see the ideal output you need for your room?
Hope this helps?