Overlanding Energy and Water Provision Planner

Plan water and power for overlanding (without guesswork)

Overlanding is a logistics game: you’re intentionally traveling where taps, outlets, and stores are scarce. Good planning isn’t about comfort alone—it’s about safety margins. This planner estimates how much water to start with, whether a planned resupply changes that number, and whether your solar + battery setup can support your daily electrical loads over the whole trip.

The calculator is intentionally simple: it treats water use as a daily average, and it treats energy as a daily balance between what you consume (loads) and what you produce (solar charging the battery). That simplicity makes it useful for early trip planning and for “what-if” scenarios (add a heater, reduce fridge use, increase solar, etc.).

Water planning model

Total water needs are split into two buckets:

• Personal hydration: daily liters per person × number of people.
• Shared cooking/cleaning: a fixed liters-per-day amount for meals, dishes, hand washing, etc.

The planner then subtracts any mid-trip resupply you expect (town stop, cache, reliable stream + treatment, etc.). The result is the starting water volume you should plan to carry.

Water formulas

Total trip water requirement (before resupply):

Where:

• d = trip length (days)
• p = people
• w = daily water per person (L/person/day)
• c = cooking/cleaning water (L/day)

Starting water to carry (after resupply):

W_start = max(0, W - W_resupply)

If you want a quick weight estimate for payload planning, water is ~1 kg per liter (2.2 lb per liter). So 40 L is roughly 40 kg (88 lb), plus container weight.

Electrical planning model (solar + battery)

On the energy side, the calculator compares your estimated daily consumption against the energy you can harvest from solar each day. It also estimates how much usable energy your battery bank holds based on capacity (Ah at 12V) and an allowed depth of discharge (DoD).

Loads: what “daily electrical load” means

The form includes three energy load fields:

• Daily Electrical Load (Wh): use this for everything except the fridge and heater if you want them itemized (lights, fan, chargers, comms, water pump, laptop, etc.).
• 12V Fridge Daily Consumption (Wh): average per day. Fridges swing a lot with ambient temperature, ventilation, and how often you open them.
• Night Heater Load (Wh): typically fan + controller power for diesel heaters (fuel energy is separate). Electric heaters are usually impractical off batteries and will dominate the budget.

The planner adds them together:

L_total = L_base + L_fridge + L_heater

Solar production: peak sun hours and efficiency

Solar array output is modeled as:

E_solar = P_solar × H_sun × η

Where P_solar is your panel watt rating, H_sun is average peak sun hours per day, and η is charging efficiency (losses in wiring, MPPT/PWM conversion, temperature, battery acceptance, etc.). In practice, many rigs see 60–90% of rated energy depending on conditions. Using the efficiency field is a simple way to derate your expectations.

Battery usable energy

The calculator interprets “Battery Capacity (Ah at 12V)” as nominal 12V storage and converts to watt-hours:

E_batt_usable = Ah × 12 × (DoD/100)

This is a planning approximation. For lithium packs, 80–90% DoD is common; for AGM/lead-acid, 50% is a more conservative cycle-life-friendly choice.

Daily net energy (surplus/deficit)

Daily balance is:

If E_net > 0, you have an average daily surplus. If E_net < 0, you have an average daily deficit and you’ll rely on battery capacity (or alternator/generator charging) to make up the difference.

How to interpret your results

Water results

• Total trip water tells you the entire requirement if you carried everything from day 1.
• Starting water after resupply tells you what you need in the vehicle at the start given a planned refill amount.

If the number feels uncarryable due to payload or storage volume, your options are: reduce usage (rationing/hygiene changes), add reliable resupply points, carry additional containers, or bring treatment and plan around known sources (with a safety buffer).

Energy results

• Daily solar energy is the average energy your array can deliver into the system.
• Total daily load is what you expect to consume each day.
• Daily surplus/deficit indicates whether the system tends to recharge or drain on an average day.
• Battery autonomy estimate (if shown by the calculator) is how many days your battery could support the deficit before reaching your DoD limit.

When the results show a deficit, you can usually fix it by (a) reducing loads, (b) adding solar, (c) adding battery (more autonomy, not more generation), or (d) adding another charging source (alternator DC-DC, generator). A helpful rule of thumb: solar fixes daily deficit; battery fixes cloudy-day tolerance.

Worked example

Suppose you’re planning a 7-day trip with 2 people.

• Daily water per person: 4.5 L
• Cooking/cleaning: 6 L/day
• Resupply: 0 L

Water:

W = 7 × (2×4.5 + 6) = 7 × (9 + 6) = 105 L

That’s about 105 kg (231 lb) of water before counting containers—often a major payload and storage constraint, which is why many trips depend on resupply or known sources plus treatment.

Now energy:

• Solar: 200 W
• Sun: 5.5 peak sun hours/day
• Charging efficiency: 90% (0.9)
• Base loads: 1800 Wh/day
• Fridge: 600 Wh/day
• Heater: 400 Wh/day
• Battery: 200 Ah at 12V, DoD 80%

Loads: L_total = 1800 + 600 + 400 = 2800 Wh/day

Solar: E_solar = 200×5.5×0.9 = 990 Wh/day

Net: E_net = 990 - 2800 = -1810 Wh/day (deficit)

Usable battery: E_batt_usable = 200×12×0.8 = 1920 Wh

If conditions match these averages and there’s no other charging source, you’d have about 1920/1810 ≈ 1.1 days before hitting the DoD limit—so this setup would need either much more solar, significantly less load, or alternator charging to be viable for a week.

Quick comparison: common build strategies

Assumptions & limitations (read before relying on this)

• Water needs vary widely with heat, altitude, exertion, illness, and diet. Treat the water estimate as a baseline and add a safety buffer for conditions.
• Resupply is modeled as guaranteed. In reality, sources can be dry, contaminated, frozen, or inaccessible. If resupply is uncertain, plan to carry more and/or have contingency options.
• Solar “watts” are nameplate ratings under ideal test conditions. Real output is reduced by panel temperature, shading, dust, suboptimal angle, and partial shading effects. Use the efficiency field to derate.
• Sun hours are an average. Weather and seasonality can swing actual production dramatically. If you need reliability, plan for worse-than-average days.
• Battery energy is estimated at nominal 12V. Actual voltage varies by chemistry and state of charge; usable energy can differ from the simple Ah×12 calculation.
• Depth of discharge affects cycle life. The “usable DoD” is a planning choice; going deeper more often can shorten battery life (especially lead-acid).
• Loads are user-estimated. Fridges and heaters are especially variable. Measure with a watt-hour meter or shunt monitor when possible to calibrate inputs.
• No explicit time-of-day modeling. The calculator uses daily totals and does not simulate hour-by-hour charging, inverter surge loads, or battery acceptance limits near full.
• Safety note: This tool supports planning but doesn’t replace route-specific risk management. In remote travel, carry extra water and have redundancy for critical power (navigation/comms/medical devices).

Practical tips to improve accuracy

• Log one “typical day” at home: measure fridge Wh/day, heater fan/controller Wh, and your baseline loads.
• Use conservative sun hours for your season/latitude and account for tree cover if you expect shade.
• For water, increase per-person liters for hot climates and high exertion, and consider an emergency reserve you don’t plan to use.