Basically, there are 4 types.
1. Top-freezer refrigerators
Top-freezer refrigerators are the most economical to buy and many still find this style of freezer section the most convenient. They are the most popular choice when it comes to capacity ranges.
This model offers a choice of pull-out or door-access frozen food compartment. While some like this style of refrigerator, others do not. This style influences the ticket price considerably and models offering a bottom freezer tend to be in the larger capacity refrigerators.
3. Side by side refrigerators
This type of refrigerator offer lots of convenience when it comes to having more frozen foods easily accessible. They're very affordable, look stylish and the narrow door swing is a good choice for small kitchens. However, they are only available in models with 450L and above.
4. French-door refrigerators
French-door refrigerators will cost you much more but with this style, it's easier to place trays and bulky items and they usually offer lots of cold food storage and an ample freezer compartment. You'll only find this style of refrigerator in the larger capacity models.
Find the best refrigerator and things to consider when buying a new one from Electrolux Refrigerators Buying Guide.
Once you've established installation and type, you can decide on capacity. If this will be your main refrigerator, size this appliance to meet your family's needs. Buying an overly large refrigerator which may remain partially empty will only use more kitchen space and increase purchase and energy costs. If you're buying a spare or beverage refrigerator, a compact model under 300L may be sufficient. A 400L size can be adequate for a family of 4, but a 510 – 620L or higher would be better for a large family.
There is generally no limit to how full it can be. Just take care not to block air vents. For best efficiency, try to keep it at least half full.