The best way of not using your stored energy, is simply don't use it. "This guys a nutter I hear you mumble". Maybe, but first consider this. My wife and I lived on our 40foot cat for 4 years and we learnt the hard way about renewable energy.
While a yacht (cruising live-aboard) as at anchor (daytime) it hardly uses any energy, but on windless overcast days the resupply is very limited.
One of the worst scenarios is underway at night. Running
lights can consume quite a lot of power, again with limited re-supply (dont switch the genset on)
So the wife and I sat down and tried to work out how much energy we were consuming in a 24 hr period. One way of saving (while in port or at anchor) was to avoid using house lighting.
In the summer, first light is around 5.00 am and last light is around 8.30 pm. That's almost 15 hours of usable daylight and on a yacht that can be a long day and by 8.30 you are usually very tired and ready for sleep anyhow. You can still have a 9 hr sleep which should be plenty to maintain your health.
So, why not arrange your days around natural light and you will hardly need artificial light.
I know it's easier for us, because we are older and don't have kidlings and are used to retiring/rising early (usually aroung 5 am every day). Sometimes having a drink around the campfire at night is all the light you need.
