That is .3 amps x 1.25 = .375 A, best use a 1 amp fuse if that is the only one on the circuit. As far as a home circuit, they are always 15 or 20A, usually 15A. the reason is that #14 size wire can carry that much (15A) for reasonable home distances, without heating up and resulting voltage drops from the line. A 20A circuit uses #12 unless it is very long, then any long run can be upsized to prevent voltage drops. These drops only reach max at full load, and seldom do we use a full 15A on a home circuit, unless we are growing weed or something like that, lol. A circuit of any kind should be sized to prevent overheating of the wire used in the circuit, any amperage draw greater then the fuse or breaker will shut it down.
A fuse of 1A on a fan motor that is .3A full load, is more than enough protection. Amps X Volts = Watts, further, Watts X 3.41 = BTU, and BTU/12000 = tons (as in 3 ton or 5 ton A/C)
If you use these, you can calculate how much cooling you will need to get rid of the heat from your total power usage in a grow system, ie. lighting, etc. Really, any resistive load. Motors are inductive loads, and more of the energy is taken as horsepower than a plain resistive load, such as an electric heater. the heat from a motor would be less per watt than a heater using the same wattage.