To answer this question, take a look at chapter 5. In this chapter, Snowball surveys the land and decides to draw up plans for a windmill. This, he says, will make the animals' lives much easier:
This would light the stalls and warm them in winter, and would also run a circular saw, a chaff-cutter, a mangel-slicer, and an electric milking machine.
In other words, by having electricity on the farm, the animals would enjoy a better standard of living. They would have lighting and heating, as well as labor-saving devices to lessen the physical burden of running the farm. In Snowball's opinion, if the animals spend less time working, they can spend more time reading and socializing with one another. These benefits are clearly demonstrated through the slogan that Snowball invents: "Vote for Snowball and the three-day week."
The windmill, therefore, represents freedom and the utopia that the animals have dreamed of. The only problem, however, is that Napoleon is dead set against it.