Our boat came with 2 CNG cylinders - one larger and one smaller. We go through the larger one about 1 per season. Costs $70-80 to refill locally. Not cheap
but worth every penny in terms of safety
and peace of mind. For now we do short coastal trips and mostly weekends liveaboard
With plans to travel further afield I picked up 2 add'l larger tanks from a marine
for $5 each. Considering they are $250 to first buy for subsequent exchanges not a bad deal. 3 large + 1 medium tank should last us at least 1 full cruising year.
No need to re-certify periodically as you just exchange the cylinders at point of sale
. If you drive to the company owned exchanges it's about $15-20 cheaper to refill. It costs them that much to transport plus the dealer's cut, etc.
We contemplated converting to LPG but since we are not yet ready to cruise
we have pushed that decision down the road, if ever. I am told by several cruisers that in most cities where there are bus/car gas powered fleets one should be able to recharge the cylinders, even if semi-officially. Especially in the poorer regions of the world where one's dollar goes much further then here. Not as easy as the LPG refills but considering safety
I'd rather cook over a charcoal Magma grill
then on an LPG stove
. But that's me.