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RV Power Consumption Calculator: How much power does my RV use per day?

Compressor fridge, lights, water pump, two phones and the laptop in the evening: together that quickly adds up to 500 to 800 Wh a day – and considerably more with a coffee maker through the inverter. This calculator adds up all loads, includes inverter losses and provides the basis for battery and solar planning.

Pick appliances from the presets or enter your own values. Result: Wh and Ah per day plus the biggest loads.

Units

12 V loads

Power per the nameplate; for cycling appliances (fridge, furnace) enter the actual running time per day.

120 V appliances through the inverter

120 V appliances

Powered through the inverter – losses and standby are added.

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Advanced settings

Result

Power consumption per day

567 Wh

Equals
44.3 Ah/day
at 12.8 V
12 V loads
567 Wh
Per week
4 kWh
Biggest load
Compressor fridge (79%)
  • “Compressor fridge” causes 79% of the consumption – optimizing here pays off most.
Show calculation
  1. 1Compressor fridge: 45 W × 10 h = 450 Wh
  2. 2LED lighting ×2: 8 W × 4 h = 64 Wh
  3. 3Charge smartphone ×2: 10 W × 2 h = 40 Wh
  4. 4Water pump: 50 W × 0.25 h = 13 Wh
  5. 5Total: 567 Wh/day ÷ 12.8 V = 44.3 Ah/day

 

How it's calculated

Every appliance uses power times time. For cycling appliances such as a refrigerator or furnace, what counts is the actual running time, not the time they are switched on.

Energy [Wh/day] = power [W] × running time [h/day] × quantity
Example refrigerator: 45 W × 10 h = 450 Wh

120 V appliances are powered through the inverter. Its losses (typically 8–15%) and its idle consumption (5–15 W while switched on) come out of the battery:

Energy from battery [Wh] = appliance energy ÷ efficiency + idle consumption [W] × hours switched on [h]
Ah/day = Wh/day ÷ nominal voltage [V]
At 12.8 V (LiFePO4), 640 Wh is exactly 50 Ah.

Worked example

A couple in a camper van: compressor fridge, LED lights, water pump, two phones, a laptop on a 12 V adapter and a coffee maker in the morning through the inverter, which is switched on four hours a day.

Inputs

  • 12 V loads:
  • Kompressorkühlschrank: 45 W × 10 h/day × 1 ×
  • LED-Beleuchtung: 8 W × 4 h/day × 2 ×
  • Wasserpumpe: 50 W × 0.25 h/day × 1 ×
  • Smartphone laden: 10 W × 2 h/day × 2 ×
  • Laptop 12 V: 60 W × 3 h/day × 1 ×
  • 120 V appliances:
  • Kaffeemaschine: 1,200 W × 0.15 h/day × 1 ×
  • Inverter efficiency: 88 %
  • Inverter idle consumption (no load): 8 W
  • Inverter switched on: 4 h/day
  • System voltage (for the Ah figure): 12 V LiFePO4 (12.8 V)

Result

983 Wh

Power consumption per day

Equals
76.8 Ah/day
12 V loads
747 Wh
120 V appliances incl. losses
237 Wh
Per week
6.9 kWh
Biggest load
Kompressorkühlschrank (46%)

Calculation

  1. Kompressorkühlschrank: 45 W × 10 h = 450 Wh
  2. Kaffeemaschine: 1,200 W × 0.15 h ÷ 88% = 205 Wh
  3. Laptop 12 V: 60 W × 3 h = 180 Wh
  4. LED-Beleuchtung ×2: 8 W × 4 h = 64 Wh
  5. Smartphone laden ×2: 10 W × 2 h = 40 Wh
  6. Wasserpumpe: 50 W × 0.25 h = 13 Wh
  7. Inverter idle: 8 W × 4 h = 32 Wh
  8. Total: 983 Wh/day ÷ 12.8 V = 76.8 Ah/day

The variables explained

Power (W)
Electrical power per the nameplate or a meter. For USB chargers, the actual charging power (phone 5–15 W).
Running time (h/day)
Actual operating time. Compressor fridge: about 30–50% of the time, i.e. 7–12 h; more in high summer.
Inverter efficiency (%)
Typically 85–92% at rated load; much worse at small loads.
Inverter idle consumption (W)
No-load draw per the data sheet while the unit is switched on.

Common mistakes

  • Calculating the fridge at 24 h: it cycles – the running time is what matters.
  • Forgetting inverter idle: 10 W over 24 h is 240 Wh – as much as half the fridge.
  • Overlooking the furnace fan in winter: 20–30 W over 8–10 h is 200–300 Wh per night.
  • Using the rated power of chargers: a 65 W laptop adapter often draws only 30–40 W on average.

Assumptions and limits

  • Presets contain typical values; your own nameplate takes precedence.
  • The inverter efficiency is assumed constant; at partial load it is lower.
  • Cable and fuse losses in the 12 V system are not included (usually a few percent).

Frequently asked questions

How much power does an RV use per day?

Frugal users with an absorption fridge on propane get by with 150–300 Wh. With a compressor fridge most are at 500–900 Wh, with an inverter for coffee, hair dryer or induction at 1,000–2,000 Wh and more.

How do I convert Wh to Ah?

Wh ÷ voltage = Ah. 640 Wh is 50 Ah at 12.8 V (LiFePO4), 53 Ah at 12 V (lead-acid). The Ah-Wh converter does this for any voltage.