The cheapy 400 watt foggers are not bad, with a few notations:
• They will not "fog out the neighborhood." I've gotten a very decent show of fog and the yard nicely covered using a 4000 watt fogger. I've used it to make a fogging witch's cauldron, a coffin with a ghoulish green glowing fog and just regular fogging with and without a chiller. It most definitely will produce fog, and I'd think this size works for most smaller haunts and applications.
• It is probably a good idea to pick up the (extra - more money

) remote timer so you don't have to have someone operate it all night (they mostly come with a push button controller - you push and it fogs, but it won't fog on its own) and you can set the length of time between fog blasts and the duration of the fog blast. All foggers require a heat-up time before they'll fog, and the 400 watt means that the heater is not nearly as strong as the bigger ones - therefore it take longer to heat up, and the duration of the fog blast isn't nearly as long. To me, it doesn't take THAT long.
• They tend to be spotty on their reliability. I've had one fogger for years doing nothing special for storage, I've bought one that wouldn't work right out of the box, and I've them crap out on me after 1 or 2 years. There are ways to fix the most likely problems (clogged nozzle/replace dry rotted tubes/gaskets) but
test it well before the big day, and keep in mind that it might not make it to next season.
• using foggers inside may cause a residue on your floor, furniture, etc... anywhere the fog goes. Most foggers use a glycol-based fog juice, and it isn't a good idea to use it any place where you have fancy stuff just to prevent residue. It's also not a good idea to have it in an enclosed space for too long as breathing the stuff isn't something you want to do all night.
• Use decent fog juice. Either the stuff that was made FOR your fogger brand, or upgrade to something like Froggy's Fog Juice. You'll get better results, and less chance of something screwing up the pump system.
• Wind is the enemy of fog. If you have a blustery night, the fog is going to be whipped right out of the area almost as fast as the fogger can make it. Try to have it in a protected area to get the best fogging effect.