Latern oil consumption
 

TFT lanterns burn 16 ounces of oil an hour. (ITL 67)

A sample of modern oil lanterns:

https://www.fireflyfuel.com/lamp-oil...-lamp-oil-last 0.33 ounces per hour.

http://www.alpharubicon.com/primitiv...ilburntime.htm 0.41 ounces per hour.

http://www.preparednesspro.com/tips-tricks-oil-lamps 0.5 ounces per hour.

My fix, on the assumption that the oil isn't up to modern standards: https://www.hcobb.com/tft/house_rules.html#equipment

Re: Latern oil consumption
 

TFT lamps use special fast-burning oil. It's better for the environment.

Re: Latern oil consumption
 

Gotta love the green worlds of fantasy!

Re: Latern oil consumption
 

Light enchantment: $500, lasts forever

Hiring an apprentice for the dungeon just to cast Light once a day: $75/week

24x7 Oil for lantern by ITL 67 numbers: $420/week

24x7 Oil for lantern with my adjustment: $17.5/week

The apprentice can actually cast at least a dozen Light spells each day, but only if he lies around resting all of the time. Two to four Light spells is more than enough and allows him to walk around with the party. (I suspect that "streetlights" are poles in the ground that have non-Wizards ride by in carriages during the day to cast Light on the tops of. Given DX 12 that's 18 successes a day. Say ST 10 DX 12 IQ 9 Light, Driver, Literacy, four other IQ points in talents, $75+$25 a week, plus an equal amount in overhead, management etc gives $11/week for each streetlamp. There is therefore one streetlamp for every $5k in household income around it.)

Note that if you keep the ITL numbers then only the richest households have any internal lighting after dark. With my numbers lower middle class households buy a quart of oil a month for an hour and a half of light each night. Upper middle class households buy a quart a week and run two lamps for three hours each night.

Re: Latern oil consumption
 

* ITL also has "phosphorescent moss" - cost: $0 if it's natural, or see new professional talent and job for moss lighting gardener specialist. (You want green, now that's green!)

* Basically though, I think you're on the right track on this one - TFT oil is expensive, and Light spells or enchantments are cheap, which undermines the "light and darkness game" and the cost effectiveness of non-magic solutions... at least to long-term lighting.

* Real lanterns have different settings. TFT lanterns may be set to give very bright light - a 6 megahex area with no combat penalties for darkness?

* ITL lantern oil also comes in convenient molotails, which are also deadly fire bombs. Maybe your cheap oil isn't so useful for mayhem?

* Hiring an apprentice to only cast Light isn't a very efficient use of a wizard.

* On the other hand, in some culturo-economic situations, training a cheap non-wizard slave to cast Light might be.

Re: Latern oil consumption
 

Modern lamp oil (derived from Kerosene) is way more efficient that plain Kerosene that was used for a few decades, which is better than Whale oil, which is better than tallow or lard or olive oil.

Technology is a wonderful thing.