Determining and Understanding the Electrical Power Requirements for Your Boat

In order to determine the ampere draw of your vessel, you need to know what electrical equipment you have and what the 12-volt amp draw is. The following is a list of typical 12-volt equipment aboard most boats and their average amp draw per hour.

12-VOLT ITEM

Bilge Pump (500 gph) --------- 2.0 AMP Draw

Bilge Pump (1000 gph) -------- 2.9 AMP Draw

Bilge Pump (1500 gph) -------- 4.9 AMP Draw

Bilge Pump (2000 gph) -------- 8.4 AMP Draw

Navigation Lights (3 mile) --- 1.5 AMP Draw

Live Well Pump --------------- 7.0 AMP Draw

Fresh Water Pump-------------- 4.0 AMP Draw

Refrigerator (12v) ------------ 6.0 AMP Draw

Ice Maker--------------------- 6.0 AMP Draw

Head (Macerator) ------------- 9.0 AMP Draw

Anchor Windlass (900lb) ------- 75 AMP Draw

12v. Housing Lighting--------- 15 per 10 Watts AMP Draw

Spot Lights (100k cp) --------- 8.0 AMP Draw

Spreader Lights (3k cp)------- 3.0 AMP Draw

Radar (24 mile) -------------- 5.0 AMP Draw

GPS --------------------------- 0.80 AMP Draw

LORAN------------------------- 0.70 AMP Draw

VHF Radio - transmit---------- 6.0 AMP Draw

VHF Radio - receive----------- 0.50 AMP Draw

Depth Sounder (LCD)----------- 1.0 AMP Draw

Depth Sounder (Color)--------- 3.0 AMP Draw

SSB - Transmit---------------- 3.0 AMP Draw

INVERTERS*

SSB receive------------------- 2.5 AMP Draw

Autopilot--------------------- 5.0 AMP Draw

Stereo (50 watt) -------------- 0.50 AMP Draw

Fan--------------------------- 1.0 AMP Draw

TROLLING MOTORS (12VOLT)

24lb Thrust------------------- 27 AMP Draw

30lb Thrust------------------- 30 AMP Draw

36lb Thrust------------------- 36 AMP Draw

42lb Thrust------------------- 40 AMP Draw

55lb Thrust------------------- 55 AMP Draw

*Inverters vary on 12-volt amp draw depending on 115-volt A/C draw. It is generally recommended by the manufacturer's that you have 20% of your inverter's voltage capacity in battery amp hour capacity in battery amp hour capacity. This should provide 1 hour of full inverter capacity. However, be sure to add additional 12-volt amp draws.

Additionally, the above amp draws are for "on-time" while the batteries are being used. Remember, a refrigerator, fresh water pump, head macerator, etc only draws power intermittently.

The information provided here has been reproduced courtesy of the Mercury Marine. Wholesale Marine reproduced this information 08/13/08