When things get tight with power and the sun she isn’t shining as much as you’d like, its the nights that are the killer.
We find, usually during the day we can break even at worse but of course there is no sunshine during the night, evenings and early mornings. So we often focus on how to remove power we don’t need overnight, whilst we are asleep,
There are a number of candidates but the obvious ones are:
- Your inverter – will consume, usually around 30W just to be ready and running. If you don’t need Mains Voltage over night, turn it off (30W = circa 2a which times a 15 hour night of no sunshine = 30Ah)
- We have a separate inverter just for the TV. Smaller but still consumes about 1A or circa 15Ah
- 4G router, Network routers, Iridium GO, Tv in standby, wifi, Radios etc. can all be turned off overnight.
Essential load draws seem to be limited to bilge pumps, anchor watch and significantly the fridges.
We have three fridge/freezers, each of which draw about 2A on average (much higher during compressor load but averages out at about 2A per hour so circa 30AH each or 90AH.
We have found with prudent pruning we can get our over night power consumption from a normal draw of around 300AH down to only 100-150AH or about what the fridges would need + essential systems.
At anchor, fridge/freezer is the big draw. The best you can do there is keep filters and compressor clean (air-cooled), strainers clean (water-cooled), and keel coolers clean (keel-cooled). Upgrading insulation around the fridge/freezer boxes is a big help. While the other loads are relatively small they do add up. You can keep an anchor watch alarm on a phone rather than main navigation and draw less power. Personally I do not turn off the VHF radio but keep it on 16. Usually I do not turn off the HF/SSB either as the overnight weather fax is usually clearest.
Underway autopilot is another big load. Offshore you can adjust the performance parameters (gain, speed, hystersis – different brands call those control settings different names to make them “easier”). You can adjust these for reduced power consumption without measurable impact on VMG. Attention to sail trim to balance forces and reduce average rudder angle also saves power.
In the third to last paragraph you write “2A per hour” which is meaningless (it’s a measure of the acceleration of electric charge). You mean 2A. Note an ampere is a measure of the speed of electric charge: coulombs per second. You got the Ah references correct.