Thanks for the comments on the Esbit. Testing is scheduled for next week (when I am on vacation). Of course it's summer here in the Southern Hemisphere, so the test results will have to be normalised for other locations and seasons.

References on the web indicate that one tablet will boil one pint of water in 8 minutes. I will try one tablet with 500ml (2 metric cups) of water and no shielding and report here.

A