The Utility properties, like Railroads, cannot be developed by the addition of Houses or Hotels and have incremental value based on the number of utilities controlled by the same player.
Utilities are the only properties without fixed rents, as rent depends on the dice roll which landed the token on the property.
Example:
- Mary's token is on Reading Railroad; on her turn, she rolls the dice and they come up with 7. Counting the spaces, she lands her token on Electric Company, which is owned by Sarah. The dice roll (7) is multiplied by 4, for a total of 28; Mary now owes Sarah $28 rent.
- If Sarah had owned both utilities, the rent would've been $70 (rice roll 7 + x10 modifier = $70)
According The Monopoly Companion's analysis, Utilities rank 10th out of 10 in payoff percentage and 8th out of 10 in visitation frequency.