National guidance is useful for planning, but local authorities may issue instructions that reflect the actual incident, water network, evacuation zone, weather warning or available support. The calculator therefore repeats a local-first rule in its generated guidance and printable plan.

What counts as an official source?

We prioritise national or state government, civil-defence, public-health, food-safety, fire-service and electricity-network sources. Where no official quantity is appropriate, the methodology labels the number as a Home Resilience Check planning assumption.

How sources are used

Official guidance is used for country-specific baselines and safety-critical rules wherever a suitable source exists. The calculator does not assume that a quantity published for one country automatically applies to another. Display-unit conversion is kept separate from the source pack, so switching between litres, US gallons and UK imperial gallons changes presentation rather than the underlying guidance.

Site planning assumptions

Some useful calculations do not have an official household standard. Examples include the simple phone-charging allowance, the optional 2× enhanced-water setting outside the UK and user-defined electrical device loads. Those values are described as Home Resilience Check planning assumptions instead of being attributed to a public authority.

Safety takes priority over arithmetic

Rules involving carbon monoxide, food safety, water-quality notices and essential medical equipment are deliberately conservative. The calculator will not turn an energy total into a claim that a heater, generator or medical device can be operated safely. Where equipment-specific judgement is required, the result tells the user what still needs to be verified.

If a source changes materially, the relevant country pack and methodology should be reviewed together so that the calculation and explanatory text remain aligned.