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DO THE MATH BEFORE YOU BUY.

Three simple calculators for sizing water, battery capacity and solar input. No account, no tracking and no personal data sent anywhere.

H2O / HOUSEHOLD

WATER RESERVE.

UK Prepare guidance cites 2.5–3 litres of drinking water per person per day as a minimum survival reference, and about 10 litres per person per day for greater comfort including basic cooking and hygiene.

Household inputs

Pets, infant formula and medical equipment can increase requirements.

RESULT / PLANNING RANGE
18 LMinimum drinking-water plan at 3L/person/day.
60 LMore comfortable planning figure at 10L/person/day for drinking plus basic cooking/hygiene.
2 × 10LApproximate 10-litre container count for the minimum drinking-water figure.
UK PREPARE GUIDANCE ↗OPEN WATER PLAYBOOK →
DC / BATTERY

BATTERY RUNTIME.

Estimate how long a power station could support a steady load. This is intentionally conservative: usable energy is lower than the headline battery capacity.

Battery & load

RESULT / ESTIMATE
7.3 hEstimated continuous runtime at the entered average load.
435 WhApproximate usable energy after the entered efficiency allowance.

High-draw heating and cooking appliances can empty portable batteries very quickly. Check both energy capacity (Wh) and output power (W).

OPEN POWER PLAYBOOK →
PV / PORTABLE

SOLAR HARVEST.

Portable solar output changes dramatically with season, cloud, shading, panel angle and charge-controller limits. Use this only as a sizing estimate.

Panel & conditions

RESULT / ESTIMATE
280 Wh/dayApproximate daily energy from the entered assumptions.
1.8 daysApproximate equivalent days to replace the entered battery energy from empty.

Always stay within the power station's solar-input voltage and current limits. Connector shape alone does not prove compatibility.

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