With the option of portable solar to boost the input the fact they may be only producing 10% of the full output still means something is coming in. Add the vehicle alternator and a 40 amp DC to DC and you have a portable generator already built into the tow vehicle. Sure it wouldn't be as cost efficient fuel wise but for the cost of the generator and the hassle of storing it/servicing it you can buy a lot of fuel. As for the difference between the generator fuel consumption and the vehicle fuel consumption at a fast idle????? Wouldn't be a lot in it. The Honda 1.0i is really only good for 600w continuous, the 40 amp DC to DC @ 14v is 560w, so it is just about apples with apples eh 
Getting the head around the amount of recharge actually needed is the biggest hurdle, you only need enough in the battery to see tomorrow morning with the system still up and running, not back to 100%, that is lead acid battery thinking. What is the over night use when you switch to minimum battery use or just revert back to how you lived when you were still on lead acid batteries? Even 100Ah over night would only mean 2 1/2 hrs of vehicle charging and that could be broken up into 5 x 30 min spells through the day if stuck at base camp. The "Jerry Can" battery in the back of the tug could be as little as a 100Ah LYP battery and a drive into town and site seeing with the return drive to camp would go a long way towards that 100Ah recharge required, transfer it into the house battery and top up with what ever is still required.
T1 Terry
