Here we will list a few downside of social events that are often forgotten, so they can be better managed.
Mental capacity: This includes all things associated with the event, from pre- to post event. You will first be stuck planning and thinking about it in general, afterwards the party and its many input signals will have to be processed. Naturally some time will have to be spent evaluating the event, even later with coworkers who consider it essential for them to be informed of the matter.
Electricity: Largely additional light, fridge and entertainment usage (radio/television). Much like above mental capacity, this may start well before the event: A freezer needs filling with food, drinks must be put in the fridge, etc.
Waste: We all like to pretend that this will not happen, but packaging alone could fill an entire dustbin, let alone all that was unwrapped but not consumed. Empty bottles are a guaranteed waste for all events.
Cleaning: This has to be done before and also after, it will use a large amount of either electricity or manual labour. Water is also possible, though this can be replaced by additional general waste of handy wipes or even more power consumption. A large amount of labour should go into tidying the place anyhow. Taking a quick look at how people get to your house may not be a complete luxury, though heavily dependent on how public that space is.
Dishes: It is generally advisable to do these before hand as much as possible, so that you are unlikely to run out during the event, though that is far from guaranteed. After the event a double load of dishes is common, meaning you will have to spend a lot of water and detergent (possible electricity).
Wear and tear: This applies to every bit of your house and garden open to the public; they will use it beyond what you would have done on your own for the evening. The chance of something breaking is also considerably higher as alcohol and crowded areas are both added to the mix. Almost all people will attempt to be attentive of your personal space, just not necessarily in the way that you would like them to be.
Transport: Often overlooked, or lied to about to ourselves as we go get groceries anyhow, but a big event can take two additional trips to the grocery store. Even with that, a last minute run is not out of the picture entirely.
