In a 26' boat, you're really limited in your ability to increase the
size of your battery bank too far, space limitations being what they
are. I would try to get at least one more battery though. Even so, you
are going to have to be very frugal with your power usage. Therefo

- Get some LED nav lights.

- Get either an LED anchor light or one of those Davis ones (we found
most people were using the Davis ones during our recently completed 2
year cruise around the Pacific).

- For interior lighting, we found that those 110v energy saving
fluorescent ones for your house were the most efficient, even allowing
for the overhead of the inverter (there are small inverters available
that have a VERY low overhead).

- Get a battery monitor (we have the Link 10). This is a requirement,
not an option. At a glance, it will tell you not only the current state
of your batteries (How many amp hours down from full are they?, What is
the current output voltage?), but also what is happening to them at any
point in time (how rapidly are they (dis)charging?).

Even so, you are going to have to be very careful. If you can do
without refrigeration as we did, this helps a lot. Doing without a
water maker (difficult in a 26' boat) helps too.

You'll find that your computer is a real power hog. Use it sparingly.

My advice would be to get the battery monitor now, then go spend a few
days or a week at on the boat away from the dock. This will tell you
what your actual needs are far better than trying to predict them by
sitting down at a desk and adding up how much each gadget uses and how
many hours a day it will be in use.

Above all, don't get so wrapped up in the details of stuff that you
forget to have a great time.