There is little point in putting a huge inverter on a small battery.
Its kind of like putting a rolls royce merlin engine from WW2 in a 78 Honda civic to run the quarter mile and allowing it a 2 gallon gas tank. It will run out of gas before it makes it to the starting line.
Many people view an Inverter as a solution to powering all stick and brick luxuries crammed into a box on wheels.
The inverter is most effective as a serious battery depleter.
Think about this, a 200 watt load is right around 16 amps, but add for inverter inefficiency and this is closer to 18 amps.
NOt accounting for the Peukert effect, which basically states that at higher loads the battery has less capacity to give(and cannot be ignored), a hundred amp hour group 27 battery, if it was healthy and fully charged when the 200 watt load was initially powered through the inverter, it could power it for less than 3 hours before the battery dropped below 50% state of charge. Account for Peukert at this load, and this is closer to 2 hours. The higher the load the bigger the toll on overall battery capacity.
About 175 to 200 watts of solar and all day would be required in a sunny environment in late spring summer or early fall for the solar to return the amount of electricity that was removed by that 200 watt load in under 3 hours. Doesn't seem fair does it?
But even an AGM battery needs 105 to 115% of the amount of energy taken from it to return to full charge.
Aged flooded batteries might require up to 150%.
So, just as it is important to match solar wattage or other charging sources to battery capacity, it is also important to match inverter size to battery capacity.
One can always have a huge inverter capacity, but in general a 200 watt inverter powering a 100 watt load is going to be much more efficient than a 1000 watt inverter powering a 100 watt load.
Bypassing the need for an inverter is wise, whenever possible.
I last used mine to power my 60 watt soldering iron, and to also power this laptop, when I was fixing my DC to DC laptop car adapter whose cord was compromised. I was going to just get a small 150 watt PSW inverter to power my Makita Li-ion battery charger for my drill driver but then I looked and saw it required 250 watts. So I got a 400 watt PSW Wagan. It does indeed pull close to 250 watts, cycling between 6 and 20 amps when charging a Li-ion battery pack.
Using an inverter to power USB charged devices might very well be the definition of vandweller wastefullness.
The inverter will likely use more battery power just turned on and powering nothing than the following product would use to charge the device.
http://www.amazon.com/TopG-Apple-Ce...d=1403062695&sr=8-16&keywords=USB+car+charger
A cleaner install is a product like this:
http://www.amazon.com/Blue-Sea-Syst...8&qid=1403065060&sr=8-1&keywords=blueseas+USB
For powering laptops:
http://www.amazon.com/Charger-Latit...=8-3&keywords=dell+latitude+e5500+car+adapter
Just replace 'dell latitude e5500' with your make and model.
Mine uses 15 to 50% less battery power than using my inverter to power the provided power brick. Been going for 3 years now, the only issues are that a Ciggy plug cannot really pass 90 watts for long before getting too hot, but that is another issue.
Some 120 volt TV's actually run on 12v DC and come with the power bricks to convert 120Vac to 12vdc. In such cases one could wire it directly to the 12v fuse block and bypass the inverter and power brick. Many DC to DC converters exist that will take 12v and step them up or down to the voltage required by a device, whether it be 14v or 19vdc or 24vdc. Using an inverter to power the appliance provided power brick which converts 120Vac to 19vdc is just plain wasteful.
Also note that inverters can cause lots of electrical interference when listening to radio, or watching OTA TV. I've heard they can also affect Wifi and bluetooth but cannot confirm or deny this. In Some devices and inverter can cause a 60 HZ buzz in amplified speakers.
Anyone wanting to power a microwave via an inverter needs a Big honking inverter, and a big battery bank, and a serious recharging source. In my opinion this a stick and brick luxury that should be avoided by those living on battery power.
It is possible to negate some of the huge battery bank and recharging sources required by running the engine while running the microwave, but lets do a little more math.
Lets say that at Idle speeds when the engine and alternator is hot, the Alternator can make no more than 50 amps( mine can only do ~32)
50 amp x 14.4v is 720 watts. Even a "700 watt microwave" will actually consume 1000 to 1200 watts, so the battery will still be having to provide ~300 to 500 watts just to feed the inverter to feed the microwave or you can place a brick on the gas pedal and hold the rpms up in the 1500 to 2000 range to bake that potato without depleting the battery. Notice that this math also ignores the additional 15% efficiency penalty caused by the inverter, and also assumes the alternator to battery and battery to inverter cabling is suffering zero voltage drop, which cannot be ignored either.
There are also a lot of reports of Microwaves having very short lifespans when powered by MSW inverters.
I think there are a few 12v microwaves out there, but their performance is not well regarded iirc.
Caseyc, I've said this before, but your chest fridge is designed to work on 12v DC and 120vac. If you are using your inverter to power it, your are simply wasting electricity and battery power. It will not get any colder on 120Vac. It will just use more electricity, about 20% more for no benefit whatsoever.
The Inverter is perhaps a Necessary evil, for some things, but employing it for everything is unwise.
Remember these is no rule that says one Inverter has to be big enough to power every single thing which might be turned on at once.
If you already own the 120vac devices you want to power then look at their power specs listed on back, or on the power brick. This is the Maximum load the device can draw, not necessarily the load the device will always draw.
Powering any device for any length of time, and you better hope it is not much more than 100 watts, unless you also have a fairly large battery bank and significant recharging resources.
Darn the 5 minute editing rule!!
One can use more than one inverter, having a smaller quieter more efficient one to power the low wattage devices, and a Big bragging rights inverter to have, just in case one cannot possibly live without a microwave or Hair dryer.