My answer is "Why would you"? :)
45W is not a charging system, it's a maintainer, for preventing slow self-discharge with loads disconnected when rig is in storage. However, for a maintainer this is overkill, 5W-10W system is enough.
LED lights and pumps will need 7-10 AH a day or more, depending on what lights and how often to pump. The smallest laptop needs at least 4 AH per hour, depending on the task, so let's say 8 Ah for 2 hours. Plus, self-discharge, detectors, occasional radio - 20 AH total. In case you forgot about DC circuit of propane fridge - often there is such a circuit - this is another 10-15 AH a day. Total 30 AH or more.
To collect 30 AH in a sunny weather with a tilted panel, you need 80W-100W panel. 120W with flat panel in summer - this is on a sunny day. Plus 10A controller. Total cost around $200 plus cables. For extra piece of mind, even with such a minimalistic approach, without microwave or any other 120V devices, I would increase the system power by at least 1.5, going for 180W panel, this wouldn't cost much more. Wattage higher than 180 would result in either 2 panels, or expensive MPPT controller.
PS: in Rv solar it's customary to measure panels in watts, and energy needs in amp-hours (AH). So don't get confused.
