First of all figure out how are you going to recharge your batteries with no shore power. Running the diesel to recharge batteries at the dock is not a good option for monetary and useful battery life issues. There are generally two types of inverters that are usually used by sailors depending on their needs. One is a rather inexpensive self contained unit which provides from 1 to 3 receptacles in a range of 150 to 1500 Watts depending on their needs. These are either connected with a 12V plug up to 400W or hard wired to the battery bank. Then an extension cord(s) is used to provide power to the individual appliances. The second alternative is a charger/inverter usually upwards of 2000W which is connected to your a/c circuit through a transfer switch. An inverter is not a substitute for shore power. First of all you have to realize that you only have approximately 100a/h (50% of capacity) of usable battery capacity without unduly hurting the batteries. From this you have to subtract your regular 12V usage (cabin lights, AM/FM radio, phone chargers, water and bilge pumps, fans or any other draws). No sense in getting a large inverter unit with limited battery capacity. TVs, computers, DVD players are usually low draw items but anything with an electric motor will usually draw significantly more and would require a larger unit and limits on running time. To place everything into perspective a 40W incandescent light bulb would draw approximately 0.3A at 120V. At 12V the draw would be tenth fold at 3A plus the inverter inefficiency of around 15% you would be looking at around a draw of 3.5A from the batteries. This means you would have enough power to burn that bulb for approximately 28 1/2 hours before it would be wise to recharge. On the other hand some appliances like a 1000W microwave oven can consume when ran through an inverter around 90A but if used for only two minutes the actual draw on your batteries will be around 3A. You would need to calculate the draw on the batteries for each appliance or fixture that you intend to use so that you can figure out in which combination they can be used and for how long. I don't know if you intend to live aboard or just would have a need for occasional a/c usage. Without shore power to keep your batteries charged I would discard the option of a charger inverter and would recommend a 750W inverter hardwired to the batteries. With an extension cord you can run power to where needed. That should provide plenty of juice to run electronics and some power tools. Check installation instructions as you will need a dry ventilated location close to the batteries and will need to add a fuse for safety. Hope all this mumbo-jumbo helps but go ahead and do your homework and read up on the use inverters.
