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Camper Power Calculator – Battery, Solar, Gas & Diesel

Daily use of your camper’s devices against battery, solar, driving and shore charging – plus how long gas bottles and diesel last.

Your devices

Our list of common camper devices, with what each draws while it runs and a typical day. Change any number, or add a device that is not in the list.

Your own device

Not in the list? Enter what it draws – it is used for this calculation only and not saved.

  • LED ceiling light

  • Dometic CFX3 35 (36 l)

  • Gas hob, one burner (1.8 kW)

  • Smartphone charging

  • Laptop (USB-C, 12 V)

  • Roof fan (MaxxFan/Fan-Tastic type)

  • Water pump (12 V)

  • Webasto Air Top 2000 STC (diesel)

Battery

Charging

Solar panels

Hours of full sun the panels get on average: about 1–2 in a central European winter, 5–6 in summer, 7 in the south. Clouds and shade lower it.

Driving (DC-DC charger or alternator)

A DC-DC charger delivers its rated current (20, 30, 50 A …); a plain split-charge relay gives lead batteries about 10–30 A on average.

Shore power (mains charger)

Gas and diesel

Self-sufficient ∞

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How to use: Camper Power Calculator

  1. 1 Keep, change or remove the example devices and add yours from the list (Dometic, EcoFlow, Vitrifrigo, Truma, Webasto …) or as your own device.
  2. 2 Adjust watts, hours a day and the share of time each device really runs.
  3. 3 Enter your battery: type, capacity and voltage.
  4. 4 Enter the solar panels and sun hours, the charging current and how long or how far you drive, and shore power if you plug in.
  5. 5 Read how many days the battery lasts, the daily balance, and how long the gas bottles and the diesel last.

About this tool

Will the battery keep the fridge cold for three days off-grid? Is 200 W of solar enough in spring? How long do I have to drive to fill the battery again? The calculator answers these with your own setup. Start from the example – a compressor cool box, LED lights, phones, a laptop, a roof fan, the water pump and a diesel heater – and change it until it matches your camper, van or caravan.

The device list holds what campers actually use, with what each draws while it runs and a typical day: compressor fridges such as the Dometic CFX3 and CRX, the EcoFlow Glacier, Vitrifrigo Slim and Engel; absorption fridges on gas; induction hobs, kettles and coffee machines through the inverter; Starlink, routers and laptops; Truma, Alde and Mr. Heater gas heaters; Webasto, Eberspächer, Truma Combi D and TimberLine diesel heaters. Whatever is missing you add as your own device – it is used for this calculation and not saved.

The battery side knows that a lithium (LiFePO4) battery can use about 90 % of its capacity and a lead battery (AGM, gel, wet) only about half. Solar is counted with full-sun hours for the season and the losses of an MPPT or PWM controller; driving with the charging current of your DC-DC charger or alternator over hours or kilometres; and the 230 V devices with the inverter's efficiency and its own consumption. The result is the daily balance, the days until the battery is empty, a 7-day chart, the inverter size you need and how long your gas bottles and diesel last.

Frequently asked questions

How long will my camper battery last?

Usable capacity ÷ daily use. A 200 Ah lithium battery at 12.8 V holds 2,560 Wh, about 2,300 Wh of it usable; with 700 Wh a day it lasts a little over 3 days without charging. A lead (AGM) battery of the same size gives only about half.

How much does a compressor fridge use a day?

Most 40–50 l cool boxes use 0.5–1 Ah per hour – about 150–300 Wh a day on a warm day, more in the heat or when you open them often. The compressor runs only part of the time, which is why the calculator has a “% on” value.

How much solar do I need?

Panel watts × full-sun hours × about 0.8 with an MPPT controller. 200 W gives roughly 880 Wh on a summer day (5.5 h) but only 240 Wh in winter (1.5 h). Size the panels so that the spring and autumn yield covers your daily use.

How much does driving charge the battery?

Charging current × battery voltage × hours. A 30 A DC-DC charger adds about 375 Wh per hour of driving into a 12 V lithium battery; with kilometres the calculator divides by your average speed.

How long does a gas bottle or diesel tank last for heating?

A Truma Combi 4 burns 160–335 g of gas an hour; at half load for 8 hours that is about a kilogram a night, so an 11 kg bottle lasts around 11 nights. Diesel heaters such as the Webasto Air Top 2000 STC use 0.12–0.24 l an hour, roughly 1.5 l a night.

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