I have a couple of 175W models, plus a 70-75W model I keep in the truck glove box for recharging cell phone, all Vectors from Wally. I generally power a laptop, recharge drill batteries and recharge cell phone, plus the occasional light
or small fan, VCR, television set, etc. I don't have anything like a hairdryer or other heat-producing appliance (I do have a heating pad, come to think of it, but never used it with inverter, and I suppose an electric blanket might be useful -- Hmm, a comparison of battery use for elec blanket on inverter vs rv furnace
might be a useful thing to know)
What I usually do with my laptop is plug the inverter into the TRUCK cig outlet and then run my 120VAC extension cable back to the egg, esp if sitting on one site for a while -- That uses power from truck battery, which will be readily recharged, rather than from egg which may not be recharged until I pull it next (being careful, of course, not to actually use a whole lot of truck battery power or I will need a jump-start from the egg!).
A hidden point here is that the higher voltage can be carried much further than the lower voltage, so an inverter of any size should be located as close to the battery as possible and wired ('gator -clipped) directly to it to prevent wiring loss. When I installed a cig lighter outlet in my Egg, I used heavier gauge wire that that for the 12VDC lights
I personally would be inclined to install 120VAC outlets and rig the inverter near the battery to power them (by plugging shore cable into inverter) than use 12VDC outlets with the inverter plugged in unless using a small inverter. This keeps the inverter's 12VDC wiring short to reduce cable loss and also means I don't have to mess with the inverter to use my laptop or whatever. Drawback is I might forget to switch the inverter off when I was finished with my task (This consideration gains importance as I gain age
PeterH is right that a large inverter (and a large load) may drain your battery rather quickly and he's also right that factory-installed cig lighter outlets may be undersized in wiring or construction.
I don't know the relative efficiencies, in terms of inverter overhead, of medium vs small inverters (Doing some research for the generator
thread, I just learned that one Honda inverter-based generator
is 6500W, so I would consider that a *big* inverter!) so don't know if there is a penalty beyond size, price and wiring for having a medium vs small inverter in your system, whether in use or standby.
I'm not convinced that anything but the inexpensive inverters are called for, because while the laptop itself may be sensitive to power problems, it is the the laptop's 'brick' or power adapter that is actually going to see the inverter's output. During the course of nine years of Full Timing, I used a number of laptops, VCRs and a color tv none appeared to be damaged by use with either the Vector or Radio Shack inverters.