As fas as saving money, you would be better off though using your stored electricity to power your a/c loads (or replacement d/c appliances) vs using the power for heating. In most places, the energy contained in natural gas is far cheaper and more efficiently used than heating by electricity.

 List of good uses for your RE power would include anything that uses a wall wart, lighting needs, low power a/c devices. Of course having both a/c wiring and a d/c wiring system throughout the house would also increase your costs for wiring them.

 As far as running your frige it does sound as though you have a system big enough to do so, however "10 panels and a dozen marine batteries" isn't enough information to go on, they could be 10 w panels, or 250w panels charging a storage system of any size.

 You would need to know the surge wattage of your refrigerator, and buy an inverter of pure sine wave( modified sine wave inverters do not run motors very well) large enough to handle the load.