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Solar panel and lithium battery calculator for campervans and motorhomes

Tick your appliances, pick the destination and the month: the calculator compares what your panels produce with what you use, shows how many days the battery lasts and what kit you would need — month by month, winter included.

Figures checked on 14 October 2026

Your consumption, your sun

The calculator opens on an example — two people, destination Brittany (France), in July, with 200 W of panels and a 100 Ah lithium battery. Replace every figure with your own.

The twelve months with your current kit

Production follows each month's sun. The chosen month's consumption stays as you entered it; in the other months, lighting follows the season (longer evenings in winter), the default fridge works harder in summer, fan and air conditioning only count in the summer months, and the rest does not change.

Daily production and consumption, month by month, at 48.1° N with 200 W of panels
Month	Production (kWh/day)	Consumption (kWh/day)	Balance (kWh/day)
January	0.3	0.7	-0.4
February	0.4	0.7	-0.3
March	0.6	0.7	-0.1
April	0.8	0.7	+0.1
May	0.9	0.7	+0.2
June	1	1	-0
July	1	1	-0
August	0.9	1	-0.1
September	0.7	0.7	+0
October	0.5	0.7	-0.2
November	0.3	0.7	-0.4
December	0.2	0.7	-0.5

Bar: average-day production. Vertical line: consumption.

Months when the sun does not cover the average day: January, February, March, June, July, August, October, November, December. Total shortfall: 60 kWh, to be made up by the battery, the alternator or a hook-up. Worst month, December: 480 Wh short every day, about 0.7 h of driving a day with a 50 A DC-DC charger. Charging without sun: alternator, shore, generator

Method and limits

One day's production = peak power × the scale's equivalent full-sun hours for the latitude × the month's share × 0.7. That factor covers panel angle, dust, heat, cables and the charge controller — it is the one the Nomad score uses.

Each latitude band spreads its sun differently over the year. At 48.1° N, December gets 0.36 times the sun of an average month and June 1.56 times. South of the equator, the calendar is shifted by six months.

The compressor fridge counts 250 Wh/day in a temperate season (the Nomad engine's value) and 393 Wh/day in summer: the middle of the 22 to 43 Ah a day Dometic publishes for its CFX3 range at 12 V, at 32 °C ambient and 4 °C inside (0.92 to 1.81 Ah per hour, from the CFX3 25 to the CFX3 95DZ). Replace it with your own fridge's datasheet figure. Across the twelve months, the chosen month stays as entered. In the other months, only lighting follows the Nomad score's seasons (×0.85 in summer, ×1 in spring and autumn, ×1.3 in winter, divided by the chosen month's own factor); fan and air conditioning only count in the hemisphere's three summer months; laptop, monitor, phones, satellite internet, induction and "Other" stay constant.

A lithium battery is counted at 85% of its capacity (the Nomad engine's value; our installation guide uses 80%, the depth of discharge at which Victron rates its LiFePO4 Smart battery for 2,500 cycles), an AGM at 50%, the depth Victron considers the most economic for that type of battery. The recommended storage covers the more demanding of two cases: one night (half the day's consumption) or a run of overcast days, when panels give only 45% of their average output.

The sizes offered are the van scale of the Azimut Nomad simulator: 100 · 200 · 300 · 400 · 600 W of panels, 600 · 1,200 · 2,400 · 3,600 · 5,000 Wh of battery. Weight: 0.055 kg per watt (rigid panel), 0.0095 kg per Wh (lithium). Base budget: £0.94 per watt, £0.6 per Wh.

This is neither an ephemeris nor a PVGIS simulation: a latitude band and a monthly share, not your roof. Shade, panel orientation and tilt, extreme temperatures and charging while driving are not modelled. Measure your real consumption before you buy.

Cabling, MPPT charge controller, cable sizes and fuses: Camper Van Solar Setup 2026 — The Complete Guide to Sizing, Wiring and Pricing

Equivalent full-sun hours a day (Nomad scale, annual average)

Latitude (north or south)	Hours
Up to 40°	6.5 h
40 to 45°	5.5 h
45 to 50°	4.5 h
50 to 55°	3.5 h
55 to 60°	3 h
Above 60°	2.5 h

The Nomad score's deliberately coarse scale: 5° bands (a single one below 40°), not a place. These are the scale's hours, before the 0.7 factor: only their product is meant to approach a real yield.

Go further

Frequently asked questions

How many watts of solar panels does a campervan need?

Divide the day's consumption by the month's equivalent sun hours (scale), then by 0.7. In this page's example (two people, Brittany (France), July), 1,008 Wh a day needs 205 W, i.e. 300 W in a common size. In December, consumption drops to 707 Wh a day (fan off, fridge working less), but the sun is missing: it would take 623 W, more than the 600 W at the top of the simulator's van scale.

What lithium battery capacity should I choose?

Enough for the more demanding of two cases: getting through one night, i.e. half the day's consumption, or riding out several overcast days in a row. With 2 days of overcast sky and 300 W of panels, the example needs 811 Wh, i.e. a 1,200 Wh battery (100 Ah at 12 V). A lithium battery delivers 85% of its capacity.

Why are solar panels not enough in winter?

Because output falls. At 48.1° N, December gets 0.36 times the sun of an average month and June 1.56 times. The example's 200 W produce 227 Wh a day in December against 983 Wh in July, 4.3 times less. The shortfall, 480 Wh a day, is mostly made up by driving: about 0.7 h a day with a 50 A DC-DC charger.

Does this calculator replace PVGIS or an installer?

No. It gives an order of magnitude from a latitude band and each month's share of sunshine, not a simulation of your location. A photovoltaic simulator such as PVGIS models a specific site; an installer checks the cabling and protection. The calculation runs in your browser, free, with no account.

What about water, food and safety?

The full Nomad score rates the four pillars of your campervan or motorhome trip — energy, water, food, safety — for your destination and your trip. Free, in two minutes.

Get my campervan autonomy score

Indicative results calculated from averages: they replace neither measuring your own consumption nor an installer's advice.