Self-Sufficiency Calculator
Self-Sufficiency Calculator PRO
Estimate household self-sufficiency for food, water, electricity, heat and reserves. Compare annual demand with your own production, storage, land use and financial value.
Household and planning period
Category weights
Food production and storage
Add crops, preserved food or animal products. Use area-based production or enter a known annual mass.
Food self-sufficiency = edible annual food energy ÷ household annual food-energy demand.
Food energy is a planning proxy. It does not confirm nutritional adequacy, diet quality, food safety or agricultural feasibility.
Water supply and storage
Rainwater volume = roof area × annual rainfall × collection efficiency.
Collected rainwater or private water may require treatment and testing before drinking. Follow local public-health rules.
Electricity generation and storage
Electricity self-sufficiency = annual own generation ÷ annual electricity demand.
Annual electricity balance does not model hourly generation, seasonal solar output, battery cycling, outages or grid-export rules.
Heating self-sufficiency
Heat self-sufficiency = usable own heat ÷ annual heat demand.
Heat demand varies with weather, insulation, ventilation, occupancy and system efficiency.
Other essential reserves
Financial summary
Replacement value and payback are simplified estimates and do not include financing, taxes, grants, degradation or price changes unless entered.
Overall score = weighted average of the enabled category percentages.
Annual supply percentages compare totals over a year and do not prove continuous independence.
Weather, seasons, crop failures, storage losses and timing of demand can reduce practical autonomy.
All calculations run locally in the browser.
Example values only — replace them with measured consumption, local climate data, product specifications and realistic yields.
Results
A self-sufficiency calculator helps a household compare its annual needs with its own food production, water collection, electricity generation, heating supply and stored essentials. The result is not a certificate of independence. It is a structured planning model that reveals where a household is strong, where it remains dependent on outside supply and which assumptions deserve closer checking.
The calculator separates annual supply from short-term resilience. A home may produce as much electricity as it consumes over a year while still relying on the grid at night or in winter. It may collect enough rainwater in total but have inadequate storage during a dry period. Keeping those questions separate makes the result more useful.
What household self-sufficiency means
Self-sufficiency can mean fewer purchases, better outage resilience or greater control over essential supplies. The calculator therefore reports several indicators rather than one unexplained percentage.
- food self-sufficiency based on edible energy;
- annual water self-sufficiency and potable storage days;
- annual electricity self-sufficiency and battery-only hours;
- heating self-sufficiency based on usable heat;
- coverage of other essential reserves;
- a weighted overall score;
- a simple average and the weakest category;
- annual replacement value and simple payback.
FAO’s food-security framework is broader than production alone. Food security also requires sufficient, safe and nutritious food to remain physically and economically accessible. A calorie-based food ratio therefore measures only one part of household resilience.
Start with the household
The food module begins with the number of adults and children and an editable daily energy assumption for each group. These values are planning inputs, not individual dietary advice.
Annual household food demand = daily household food energy × 365.
Actual needs vary with age, activity and health. The calculator does not prescribe a diet; it creates a consistent denominator for comparing scenarios.
Add food items in two different ways
Up to 30 food items can be entered. The area-based mode suits crops with a known growing area and expected yield. The direct-output mode suits eggs, milk, meat, honey, stored staples, preserved food or any product where the annual usable mass is already known.
Area-based production
Gross annual mass = growing area × yield per area per harvest × harvests per year.
The model then applies harvest and storage losses:
Edible annual mass = gross mass × (1 − loss percentage).
Finally:
Food energy = edible mass × kcal per unit mass.
Known annual output
Enter the annual mass directly, then add its food energy, loss percentage and replacement price. This prevents the calculator from forcing every product into a land-area model.
Use reliable food-composition data
Energy per kilogram should come from a recognised food-composition source or a product label. The UK Composition of Foods Integrated Dataset consolidates official composition data for foods commonly consumed in the UK. France’s ANSES Ciqual table provides energy and nutrient information for thousands of foods representative of French consumption.
Match the database entry to the edible product. Raw, cooked, dried and preserved foods can differ greatly in water content and energy density.
Why losses belong in the calculation
Garden and smallholding plans often compare gross harvest with household demand and overlook spoilage, trimming, pests, failed storage or food that never reaches the table. FAO treats food loss and waste as a significant food-system issue and provides household guidance on storage and waste reduction.
Use a low loss assumption only when records support it. Weighing harvest, storage and consumption over one season improves the next calculation.
Food self-sufficiency and reserve days
Food self-sufficiency = annual edible food energy ÷ annual household food-energy demand × 100%.
A result above 100% means the entered annual energy exceeds the planning demand. It does not prove that the diet contains enough protein, fat, vitamins, minerals or variety.
Stored-food reserve days use a different formula:
Reserve days = stored edible food energy ÷ daily household food demand.
This value describes stored energy, not future harvests. It can expose a household that produces well annually but keeps little food through winter.
Land use and additional land
The calculator totals the growing area of area-based food items and compares it with available productive land. It also calculates average edible energy per unit area.
Additional land for the target = missing annual food energy ÷ average edible energy yield per area.
This projection keeps the entered crop mix. It excludes rotation, paths, livestock feed, irrigation, soil fertility and labour, and it says nothing about dietary diversity.
Annual water demand
The water module combines daily use per person with additional household demand.
Annual water demand = (people × daily use per person + other daily use) × 365.
Separate total household use from emergency drinking-water storage. Normal use can be large, while potable reserves are smaller but more critical.
Rainwater collection
In metric units, one millimetre of rain falling on one square metre equals one litre before losses.
Theoretical collection = roof area × annual rainfall × collection efficiency.
The efficiency factor covers first-flush diversion, overflow and other losses. Use long-term local rainfall rather than an unusually wet year.
WHO publishes sanitary-inspection guidance for rainwater collection and storage. Its materials emphasise contamination risks and corrective actions. Rainwater intended for drinking requires suitable system design, treatment or disinfection and compliance with local public-health rules.
Annual water percentage versus stored autonomy
Annual water self-sufficiency = annual own water supply ÷ annual water demand × 100%.
Own supply can include rainwater and a reliable private source such as a tested well. Storage autonomy is calculated separately:
Potable storage days = usable stored water ÷ daily potable-water need.
An annual surplus does not guarantee supply through a dry period. Detailed tank sizing needs a monthly or daily model.
Electricity self-sufficiency
The electricity module uses installed solar capacity, expected annual yield per installed kilowatt and other generation.
Annual solar generation = installed capacity × annual yield per kW.
Electricity self-sufficiency = annual own generation ÷ annual electricity demand × 100%.
The European Commission Joint Research Centre provides PVGIS for location-specific solar and photovoltaic estimates. Use a local result, installer simulation or measured data instead of a broad country average.
Why annual electricity balance is not off-grid autonomy
Annual generation and annual consumption can be equal while their timing remains completely different. Summer exports cannot automatically cover winter imports, and midday generation cannot power a night-time load without storage or another supply.
PVGIS also offers an off-grid tool that uses time-varying consumption and battery storage. That level of modelling is more appropriate when the goal is continuous independence rather than annual accounting.
The calculator therefore reports battery-only autonomy separately:
Usable battery = nominal capacity × usable percentage × battery/inverter efficiency.
Battery hours = usable battery ÷ average hourly electricity demand.
Average demand is not a peak-load test. Starting currents and battery power limits still require technical review.
Heating self-sufficiency
The heat module can use a known annual heat demand from bills or metering. When that value is unavailable, it can estimate demand from heated floor area and an editable energy-intensity input.
Estimated heat demand = heated floor area × annual heat intensity.
Usable own heat = own heat supply × usable percentage.
Heat self-sufficiency = usable own heat ÷ annual heat demand × 100%.
Heat intensity varies with climate, insulation, ventilation and system efficiency. Replace a generic value with measured demand when possible.
Other essential reserves
The reserves section compares available days of essential supplies with a target duration. It can represent hygiene products, lighting supplies, household consumables or another resource the household considers critical.
Reserve coverage = available days ÷ target days × 100%.
Use separate inventories for items with very different shelf lives or failure consequences.
Weighted score, average and weakest category
The weights let the user define priorities. They are normalised automatically, so they do not need to total 100.
Overall score = sum of capped category score × category weight ÷ sum of weights.
Each category is capped at 100% only for the overall score. Detailed results retain a real surplus above 100%. This prevents a large electricity surplus from hiding inadequate water or food.
The calculator also reports a simple average and critical minimum. The weakest category is often the most useful resilience signal.
Critical stored-resource autonomy
The calculator compares food reserve days, potable water days, battery-only days and other reserve days. The shortest value becomes the critical stored-resource autonomy.
It answers which stored resource would run out first if outside supply stopped.
Replacement value and payback
Each food item can carry a replacement price. Water, electricity and heat use editable unit prices. The calculator counts only the portion of own supply that replaces demand, so a large theoretical surplus does not automatically create extra savings.
Gross annual value = food + water + electricity + heat + other savings.
Net annual benefit = gross value − annual maintenance.
Simple payback = capital cost ÷ net annual benefit.
This simplified payback excludes financing, taxes, grants, degradation, replacement equipment and future price changes.
Common mistakes
- treating annual balance as continuous independence;
- using gross harvest without storage losses;
- mixing raw and cooked food energy values;
- counting the same growing area twice;
- using rainfall without a collection-efficiency factor;
- assuming rainwater is automatically potable;
- using battery energy without usable capacity and efficiency;
- ignoring winter heat and solar seasonality;
- letting one surplus category hide a critical deficit;
- treating simple payback as a full investment appraisal.
Frequently asked questions
Can the calculator prove that a household is fully self-sufficient?
No. It compares entered annual supply, demand and storage assumptions. Continuous independence needs seasonal and time-based analysis.
Why does the overall score cap categories at 100%?
The cap prevents a large surplus in one category from compensating for a shortage in another category.
Does food self-sufficiency confirm a healthy diet?
No. The food ratio uses edible energy and does not assess complete nutrition, safety or dietary variety.
Can collected rainwater be entered as drinking water?
Only after suitable treatment, testing and compliance with local health requirements.
Why can electricity reach 100% while battery autonomy remains low?
Annual production may match annual use even when generation and demand occur at different times.
Should I use national averages?
They can support an early scenario, but measured household and local climate data are better for planning.
Official and primary sources
- FAO Committee on World Food Security: Global Strategic Framework
- FAO: Food Loss and Food Waste
- UK Government: Composition of Foods Integrated Dataset
- ANSES: Ciqual nutritional composition table
- WHO: Rainwater collection and storage
- WHO: Household water treatment and safe storage
- European Commission JRC: PVGIS
- European Commission JRC: off-grid PV systems
- International Energy Agency: energy data and statistics
Sources reviewed: 22 June 2026.
