Methodology

Home Resilience Check is a planning model, not an emergency prediction engine. Every result is derived from the household details, outage switches, stored supplies and assumptions shown below.

Scenario endurance, baseline preparedness and score

Scenario endurance is the primary day-based result: the lowest modelled coverage among consumable resources actually affected by the selected disruption. Communications-only and other non-consumable failures are reported qualitatively instead of forcing a meaningless day count. Baseline preparedness is shown separately and checks a three-day water reserve, three-day usable-food reserve and the core household kit. This prevents a fully powered scenario from hiding a basic food or water gap.

The 0–100 scenario score is secondary. It uses only relevant outage dimensions plus a smaller core-kit component, then applies caps when critical or important gaps remain. A household with no emergency lighting during a power cut, no broadcast fallback during a communications outage, or other critical unresolved dependencies cannot receive a reassuring 80+ score. None of these outputs predicts safety or survival.

Water

Each supported country has a separate official baseline: UK 3 L/person/day within the government’s cited 2.5–3 L minimum range; US 1 US gallon/person/day; Canada 2 L/person/day; Queensland/Australia 10 L/person over three days; New Zealand 3 L/person/day. The enhanced-reserve option uses the UK government’s approximately 10 L/person/day comfort figure in the UK; elsewhere it is a clearly labelled Home Resilience Check planning setting at 2× the official baseline. Pet water is never guessed: users enter the total amount they want reserved for pets per day.

Food

Food is measured in household-days, with a second input for how much of that stock is ready-to-eat or needs no cooking. If the selected cooking method is unavailable, food that requires cooking is not counted as usable. Rather than merely reporting “27 days missing”, the result also converts the gap into person-days and approximate meal slots at three eating occasions per person per day. Meal slots are a scale visualisation only, not nutrition or calorie guidance. Infant feeding remains outside the generic arithmetic.

Stored electrical energy

The basic phone model uses 18 Wh per basic phone charge plus a 20% planning margin. This is a Home Resilience Check assumption, not an official standard. Users can add their own electrical loads using quantity × rated watts × hours/day × outage days. Backup electric heating is calculated separately as watts × hours/day × outage days and then included in the combined stored-energy target when mains electricity is unavailable.

Stored battery capacity is entered as nominal Wh. A separate optional usable-battery/conversion factor lets the user apply their own manufacturer or tested figure; it defaults transparently to 100% rather than assuming an efficiency. Large results are shown in kWh with the underlying Wh retained for precision.

Watt-hours alone do not prove a battery or power station can run an electric heater or heat pump. Continuous output, start-up demand, inverter limits, connection method and appliance/manufacturer requirements must also be checked. The site therefore treats the heating calculation as an energy-budget estimate, not an equipment-compatibility or safety guarantee.

All water calculations are stored internally in litres, then displayed as litres, US customary gallons or UK imperial gallons. Auto mode defaults to US gallons for the United States and metric litres for the other supported countries. Changing display units converts the same canonical quantity; it does not change the country guidance baseline. Electrical energy remains in W, Wh and kWh because those units are universal.

Units and conversion

Dependencies

Electric cooking is treated as unavailable in an electricity outage. Gas cooking is unavailable in a gas outage; during a power cut, some gas appliances may work while others depend on electric ignition or safety systems, so the site flags verification rather than assuming. Gas/fuel boiler or furnace heating is treated as electricity-dependent because modern systems commonly require powered controls, pumps or fans; UK Prepare explicitly states that gas boilers will not work without power.

Safety rules

The model never recommends using a BBQ, camping stove or portable generator indoors. Carbon-monoxide safety is a hard-coded warning, not AI-generated advice.