Sleeper cab power usage calculator: what a night in the bunk draws
Enter your appliances and how long they run. The sleeper cab power usage calculator returns watt-hours for the night, the battery bank that covers it, and what idling or an APU would burn instead.
Watt figures are EXAMPLE label ratings, not a product. Read the label on your own gear; set hours to 0 for anything you do not run.
Night length, inverter and fuel assumptions
POWER TONIGHT
1,148 Wh
about 96 amp-hours from a 12 V bank
- Fridge 500 Wh
- Microwave 196 Wh
- Laptop and TV 212 Wh
- Fan 240 Wh
- Electric blanket 0 Wh
- Bank needed at 50% usable
- 191 Ah
- Your 200 Ah bank covers
- 100% of the night
- Idle all night (10 h)
- 8.0 gal, $49.59
- Diesel APU instead
- 3.0 gal, $18.60
- Batteries alone
- no fuel tonight
Your bank covers tonight with room to spare, which would save about $49.59 over idling.
Formula: watts x hours for each load, plug-in loads divided by inverter efficiency, total divided by 12 V. Bank needed = amp-hours / usable share. Fuel = hours x burn rate x price. Heat and air conditioning draw far more than these loads.
POSTED: DOE Vehicle Technologies Office, Long-Haul Truck Idling Burns Up Profits (2015) · checked Oct 2026
A 1,148 Wh night is easier when the day ends at a stop you trust. Dispatch runs 5% of gross for one truck, and you confirm every load.
By Nathan Beck, Truck dispatcher · Updated October 2026
Every appliance in the bunk runs off your batteries once the engine is off. This sleeper cab power usage calculator adds up a night of use in watt-hours, shows the battery bank that covers it, and compares that with what idling or a diesel APU would burn for the same night. Use the label on your own gear; the defaults are examples.
How it is calculated
- Each load: watts times hours. Minutes are converted to hours.
- Inverter loss: plug-in loads, such as a microwave, laptop or TV, are divided by the inverter's efficiency, because some power turns to heat.
- Amp-hours: total watt-hours divided by 12 volts.
- Bank needed: amp-hours divided by the share of the bank you can safely use.
- Coverage: your bank's usable amp-hours divided by tonight's amp-hours, capped at the whole night.
- Fuel instead: hours parked times the idle or APU burn rate, times your diesel price.
The DOE fact sheet behind the defaults puts heavy truck idling at 0.8 gallons per hour within a range of 0.6 to 1.5 gallons per hour, and a diesel APU at 0.2 to 0.5 gallons per hour (diesel APU). The diesel default is the EIA U.S. average of $6.199 a gallon.
POSTED: DOE Vehicle Technologies Office, Long-Haul Truck Idling Burns Up Profits (2015) · checked Oct 2026
What a good result and a bad result look like
A good result is a bank that covers the whole night with room left over, so you wake up with power to start the day and no idle hours burned. A bad result is a bank that runs out at 03:00, which means a dead fridge, a warm bunk, or idling after all. The fix is usually one of three things: run the big loads, like a microwave or coffee maker, while the engine is on; add battery capacity; or plan nights where you can plug into shore power.
This tool covers the steady loads in a sleeper. Heating and air conditioning draw far more, and most drivers handle them with a diesel bunk heater, an APU or a battery cooling system built for the job. Our truck driver sleeper cab guide covers the setup side, the idle cost calculator shows what idling costs over a year, and the APU payback calculator shows whether an APU earns back its price.
Nights that start in the right place
A good night in the bunk also depends on where you park and how much time you have to rest. Our dispatchers plan loads around your hours and the stops you prefer, so the day ends with time to plug in, cook and sleep. If you are weighing the cost of that help, the dispatcher fee calculator puts it in dollars. Every load waits for your yes, and the rate con comes straight to you. See how we plan long runs on the OTR dispatch page, the HaulStop home page for everything we do, or apply in about two minutes.
Sleeper Cab Power Usage Calculator questions
How many amp hours do I need in a semi sleeper?
Add up the night first. A sleeper running a fridge, a few minutes of microwave, a laptop and a fan can draw around 1,000 watt-hours, roughly 90 amp-hours from a 12 volt bank. Because most batteries should not be drained all the way, you need a bank rated well above that: about 180 amp-hours at 50% usable, or about 113 at 80%.
How much power does a truck fridge use overnight?
It depends on the fridge, the weather and how often you open it. A compressor fridge cycles on and off, so its average draw is much lower than its running draw. Check the maker's label or manual for average consumption, or measure it with a meter, and enter that average in the calculator rather than the peak figure.
Can I run a microwave off my truck batteries?
You can, through an inverter big enough for it, but it draws a lot while it runs and the inverter loses some power as heat. A short run is fine on a healthy bank. Running a microwave or coffee maker while the engine is on, or on shore power, saves your batteries for the loads that run all night.
Is it cheaper to run an APU or idle overnight?
On fuel, an APU usually burns far less. The DOE puts a heavy truck at about 0.8 gallons an hour at idle, against 0.2 to 0.5 for a diesel APU. A battery system burns no fuel at night but needs recharging. Whether an APU pays back its price depends on your hours; the APU payback calculator works that out.
PARK BY: PLANNED WITH YOU
Rest well, then roll
We aim each day at a stop that suits how you rest. You confirm every load.