Off-Grid Van Life Power Calculator

How large a battery do you need for off-grid van life? What about the DC-DC charger and size of solar panel(s)? Do you need to up-rate your alternator?

Now you can find out!

This calculator assumes that you have no electric hook-up. It does not calculate for a simple split charge relay, but you can probably figure that out from the results it gives you.

You need a browser that supports Javascript for this to work!

The calculator is approximate. Use it as a rough guide only! It may contain errors. A safety margin is added to the results to make it a bit better. Don't add another safety margin yourself!

Your Habits

Pick a typical worst-case day, with minimal driving and lots of time in the van!

How long will you spend inside your van per day (not including sleeping or driving)?

1 hour 2 hours 3 hours 4 hours 6 hours 8 hours 12 hours 16 hours

How many times a day will you drive your van? (pick the lowest that applies)

Once every other day
Once a day
Twice a day (morning and after dinner)
Three or more times a day (morning, after lunch, after dinner)

How long will you spend driving your van per day (total for all trips in a day)?

30 mins 45 mins 1 hour 1 hour 30 mins 2 hours 3 hours 4 hours 6 hours

What times of year will you be camping?

Below-freezing Winter Days Above-freezing Winter Days Spring/Autumn Summer Heat Waves

How many cuppas per day will you make?

None 1 2 4 6 8 12 16 24 512

What sort of meals will you cook in the van?

None Simple heating on a hob or microwave Complex meals or use of an oven

How many people will be staying in your van?

1 2 3 4 5 6 One man, one Karen and 800 kids

How many amps is the alternator in your van? (if unknown, it's probably about 80A for an old van and 180A for a newer one):

80A 90A 100A 120A 140A 160A 180A 200A 225A 250A

Your Van's Accessories

Heating
It's assumed the heater is used proportional to the season
None
Wood burner
Gas catalytic heater (Mr. Buddy etc.)
Diesel or gas blown-air heater (Chinese diesel heater, Webasto, Propex, Truma etc.)
Engine coolant heater with cabin fan (Webasto Thermo-Top etc.)
Electric blanket per-person (12V)
2kW electric fan heater

Air Conditioning
None
Evaporative cooler
Air conditioner

Water system
Shower
Reverse-osmosis greywater system (not a Showerloop / recirculating shower)
Electric water tank heaters (to prevent tanks mounted under van freezing)
No hot water supply
Gas or diesel water heater (including Bobil Vans kit for Chinese heaters)
Electric tank-type water heater
Electric point-of-use water heater

Refrigeration
Use is proportional to weather
None
Ice box
Gas or 2-way/3-way fridge or fridge-freezer
Cheapy 12V cool box (Peltier-type)
12V compressor cool box
12V fridge
Small 120V/240V fridge
Full-size 120V/240V fridge-freezer

Cooking
Gas hob/stove
Electric hob/stove (induction or other type), two rings
Gas oven
Electric oven
Microwave
Electric kettle (1kW travel type)

Ventilation
Roof extractor fan for cooking
12V desk fan for hot days
Continuous ventilation fan
Vehicle cabin blower fan for ventilation on low, on intermittent timer (1/4 of the time)

Loo
None
Chemical toilet
Composting toilet without fan
Composting toilet with fan
Gas incinerating toilet (shit burner)
Electric incinerating toilet (e-shit burner)

Entertainment
A single laptop
One laptop per person
Car stereo (from camping battery)
Small television
Large television
Playstation / Xbox
Commodore Amiga 500
CCTV system (used 24/7)
Mobile router
Smartphone (one per person)
Rail gun
How much will each entertainment device be used while you're in the van?
1/4 the time 1/2 the time 3/4 the time All the time

Results

Solar panel wattage	No solar	100W	200W	300W	400W	500W	600W	700W	800W
Recommended battery size in Ah, lead acid	?	?	?	?	?	?	?	?	?
Recommended battery size in Ah, lithium	?	?	?	?	?	?	?	?	?
DC-DC charger amps, exact	?	?	?	?	?	?	?	?	?
Solar charge controller amps, minimum	None	10	20	30	40	50	60	70	80
Recommended inverter watts	?
Summer idle hours	?	?	?	?	?	?	?	?	?
Spring/autumn idle hours	?	?	?	?	?	?	?	?	?
Winter idle hours	?	?	?	?	?	?	?	?	?

What does this table mean?

It shows you how your component choices will vary according to your solar system size.

The idle hours are very important.

This tells you how many hours you'll need to idle the van's engine every day to replenish the battery.

Ideally you want all 0s here. Otherwise it means you have a shortage of power sometimes.

But I don't want to idle the engine at all!

In this case, go back to the drawing board! You're using too much bloody power.

Alternatively, upgrade your van's alternator to a higher amperage one. Then your battery can charge faster during normal driving.

Or change your habits. Drive more, spend less time in the van.

Why is the amount of idling shown separately for each season?

Most people camp during the summer months. Electrical demand is often lower in the summer (no heaters). Your solar (if fitted) is more productive. You may find no engine idling is required in the summer.

They are shown separately so you can decide whether it's OK based on your habits. You might not mind idling in the winter?

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