One way to get consistent power is to have an excess of generating capacity by building
multiple generating units, each charging a smaller battery, all feeding into a larger
battery bank. You then use a little automation to toggle each generator unit on or off
when the attached smaller battery fills or empties. Despite an excess of capacity, because
each generator spends some fraction of it's time turned off, you consume roughly the
right amount of fuel on average (there is a cooldown/re-heating cost on the boiler, but
this is fairly small during constant or near constant operation, and during occasional
use the total cost is so small that even a large fractional waste is negligible)
The same approach can be used to have the enormous multiblock generator efficiently
power much smaller machines - you have the machine draw a small amount of power from
a battery, and use automation to have the generator top the battery back up once it falls
below a certain level.
The key in both cases is to physically and logically decouple the generation and consumption.
All of your generators feed into a central pool, all of your consumers draw from that pool.
Beyond fuel efficiency, the other advantage of this approach is that the same few generators
can power any of the dozens and dozens of machines in your base. This splits the costs
of expansion into two parts: at first you can build a wider variety of machines, to give you
flexibility and efficiency in the components you manufacture; later you can build more
generators to give you improved productivity by allowing you to run more machines