Global Solutions · Calculator Centre
Seven working calculators. Every one shows its formula, its assumptions and its limits. They run entirely on this page — nothing you type is sent anywhere. Prices and tariffs are yours to enter: we invent none.
Assumes rain is spread across the year and the whole roof drains to the tank. Real systems lose water to first-flush diversion, splashing and dry-season timing — size storage for the dry months, and treat drinking water properly.
Wattage is on each appliance's label. Fridges and freezers cycle on and off — count roughly a third to a half of the day as running time. Months are taken as 30 days.
A 1:2:4 nominal mix suits many non-structural and lightly loaded uses in teaching examples — it is NOT a structural design. Foundations, beams, columns and suspended slabs must use the mix and reinforcement your engineer specifies.
Assumes standard 450 × 225 mm block faces. Deduct large door and window openings from the wall area before calculating, or keep them in as your safety margin — say which you did.
Use one currency throughout and one consistent period (usually a month). Break-even is a survival line, not a success line — and it assumes every unit produced is sold.
The 0.75 factor is a common planning allowance for heat, dust, wiring and conversion losses. This is a conversation starter for installer quotations — never an installation design.
Runs only on this page; nothing is stored or sent. Use your real last-month figures — a budget built on wishes fails by February (see the Financial Literacy department).