Power consumption of standalone electric fans vary and many have multiple speed settings. They can use anything from 10-250W, but a domestic fan will use about 100W. 

Therefore in an hour a typical fan will consume 0.1 kWh of energy which equates to carbon emissions of:

0.1 x 0.527 = 0.0527 kg CO2 per hour ¹

For a duration of 6 hours through the day, CO2 saved will be:

0.0527 x 6 = 0.32 kg CO2 per day 

 
Air-conditioning units are real energy guzzlers, and can consume anything from around 1000W to 9000W. ² Assuming a typical mid-range air-conditioning unit of 3,000W or 3 kW ³ will result in carbon emissions in an hour of:

3 kWh x 0.527 = 1.581 kg CO2 per hour

or 9.486 kg CO2 for a duration of 6 hours through the day.

Domestic air conditioners are much rarer in the UK than office installations, although sales are beginning to rise as the climate warms. However they are particularly common in some countries like the US, where at least 75% of homes have one.  For this reason we'll take a weighted average of these two figures, giving air-conditioning a 25% weighting, and electric fans 75%.

So average carbon saved by switching off is:

[0.75 x 0.32] + [0.25 x 9.486] = 0.24 + 2.372

= 2.61 kg CO2 per day by switching off fans and air con.