Generator Load Management Basics

To understand how battery chargers, automatic generator start systems and other baseloads affect your generator, you need to be aware of three things:

  1. Your generator’s power capability
  2. How to manage electrical loads
  3. Battery charging times

Managing RV Generator Loads

Determining Your Generator’s Power Capability

To determine what your generator can power, use the chart to estimate the total combined watts of all the appliances, lamps, battery chargers, air conditioners and other electrical products you typically use at the same time. (All electrical appliances and lights are labeled with their power requirements expressed in watts or amps). You can use any number of appliances simultaneously, as long as their combined wattage doesn’t exceed the electrical output of your Onan® or Camp Power™ generator, or your RV’s circuit breaker rating.

Appliances Average Required Wattage Amps
Air Compressor (1hp) 1500-2000 9-20
Air Conditioner 1400-2400 9-20
Battery Charger Up to 3000 6-28
Blender 600 5.5
Broiler 1350 12
Broom/Vacuum 200-500 1.5-4
Coffeepot 550-1000 4-8
Compact Disc Player & Speakers 50-100 0.5-0.9
Computer 50-100 0.5-0.9
Converter 500-1000 4-8
Curling Iron 20-50 0.2-0.5
Dishwasher 1400 12
Drill 250-750 2-6
Electric Blanket 50-200 0.5-1.5
Fan 25-100 0.2-0.9
Frying Pan/Wok 1000-1350 8-11
Hair Dryer 350-1500 3-13
Iron 500-1200 4-10
Lightbulbs 40-100 ea. 0.36-0.9
Microwave/Convection Oven 700-1500 6-13
Radio 50-200 0.5-1.5
Refrigerator 400-1000 3-8
Space Heater 1000-1500 8-13
Stove (per element) 350-1000 3-8
Television 200-600 1.5-4
Toaster 750-1200 6.5-10
VCR 150-200 1.15
Washer/Dryer 2000-2250 16
Water Heater 1000-1500 8-13
Water Pump 500-600 4-5

Managing Electrical Loads

If you try to operate too many things at once, you’ll “overload” the generator. You’ll know because your lights will flicker or the circuit breakers on the generator or the main coach electrical panel will trip open, stopping the flow of power. Battery charging loads can also overload your generator and you may not realize this is happening because the charging starts automatically. Be aware of how large this “invisible” load can be.

  • Air conditioners need “reserve” power to start. Too much baseload can prevent air conditioners from starting.
  • Air conditioners typically draw 1400-2400-watts, depending on size and operating conditions (more power is needed at high temperature or humidity). During start-up, air conditioners can draw 3-4 times that amount.
  • Battery chargers come on automatically and can draw a large load (up to 3000-watts). Manage your electrical loads by adjusting battery charge rates to best suit your needs. Consult your inverter/charger manual or manufacturer.
  • If you have an automatic generator stop/start system, learn how to control it. Consult your inverter/charger manual or manufacturer for adjustment procedures. Adjust battery charge rates to best suit your total electrical needs. This system is not part of an Onan® or Camp Power™ generator.
  • Disable auto-start systems while refueling, servicing, storing or long-term parking.

NOTE: The generator will continue to run after a circuit breaker trips. Turn off all appliances and reset the breaker. If the breaker trips again with all electrical loads off, you may have a short circuit in your wiring. Turn off the generator and contact a qualified electrician.

Inverter/Converter Size (Watts) Battery Charger Max Output (14vdc) Amps Required From Generator (at 120VAC) Watts Equivalent Appliance Load Example
1000 50 Amps 12A 1440 Hi-efficiency AC or microwave
1500 75 Amps 16A 1920 Hi-efficiency AC plus microwave
2000 100 Amps 21A 2520 11000 AC plus microwave
2500 120 Amps 26A 3120 13500 AC plus microwave
3000 140 Amps 28A 3360 11000 AC plus 13500 AC

EXAMPLE: Highlighted box shows that a 2000-watt inverter running at 100A battery charge capacity creates the same load as an 11000 BTU air conditioner plus a microwave oven.

Understanding Battery Charging Times

In addition to being aware of battery charging loads, it is important to know that battery charging takes time. The chart below shows how long a 100A charger must run before reaching 100% battery charge.

Battery chargers replenish power drained from:

  • engine starting
  • generator starting
  • appliances working on inverter power like microwave and refrigerator
  • mechanicals like slide outs and pumps

NOTE: Table is for a 100A battery charger (typical 2000-watt inverter) pulling 21A (2520-watts) from generator, depending on battery bank size.

Battery Charging Times
Battery Bank Size (Amp Hours) Hours That A 100A Battery Charger Must Run To Reach Float Rate Starting From This % Of Battery Charge.
80% 60% 40% 20% 0%(11 VDC)
100 0.3 0.7 1 1.3 1.6
200 0.6 1.4 2 2.6 3.2
400 1.2 2.8 4 5.2 6.4
600 1.8 4.2 6 7.8 9.6
800 2.4 5.6 8 10.4 12.8
1000 3.0 7.0 10 13.0 16.0
1200 3.6 8.4 12 15.6 19.2
1500 4.5 10.5 15 19.5 24.0

EXAMPLE: Highlighted box shows that using a 100A battery charger, a 600A/hr battery bank at 60% charge level must be charged for 4.2 hours before it is fully charged.

Conditions that increase battery charge times:

  • If too many DC loads like pumps and fans are applied, the charger may never catch up with the batteries. The Battery Charging Times Chart assumes no other DC loads are operating.
  • 120v air conditioning loads powered through the inverter lengthen charge time due to power sharing. Consult your inverter/charger’s manufacturer manual for charge rate control.
  • Poor batteries, cables, or connections.

Manage electrical loads to get the most from your generator and electrical system. If you need help, ask your coach dealer for training on how to operate auto-starting systems as well as how to adjust battery charger output. If the dealer can’t help, contact inverter/charger or control manufacturer.

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