Hello Lynne,
Our group has used a generator in the past [quite a while ago], but I can't speak for how efficient this was. Gas bottles can be a problem if it is very cold-twice I have had them malfunction in frost, but that was March both times. The other way I have tried is using pump pots, filled at the nearest indoor CP-practical if distances not too great, but the capacity might be a problem with a big event if refilling not quick [could re-fill from on site heated water-keeps things moving a bit].
How about asking Northumberland what they did at their outdoor CPs after Dufton? Those were some cold and exposed places and remote, so they may have a suggestion.

In the past I have only had experience of providing hot water for drinks at an outdoor check point using gas rings and pans/kettle. I am wondering if it might be easier and safer to run my plug in water heater from a portable generator? Thinking ahead to the TP100 for numbers of drinks needed. Rent or buy a generator? what size? still take gas as a back up? All advice and shared knowledge and experiences very welcome, thank you.