The problem
Everybody wants to know what an appliance costs to run before they buy it, and every tool that answers it wants a login first. Most also assume one country's tariff and one language.
What we shipped
- A live cost card with no Calculate button: daily, monthly and yearly figures move as the hours slider moves
- 98 appliance presets across 12 categories, plus manual wattage for anything not in the list
- Electricity rate and currency defaults for 47 countries, from Rs 40 a unit in Pakistan to $0.16 in the United States
- An advanced drawer for peak-rate windows, duty cycle, power factor, voltage and standby draw
- Solar sizing against 39 countries' own peak sun hours, system losses and optimal tilt, with a stated global average as the fallback
- Eleven languages including Arabic and Urdu laid out right to left, and a PDF report generated on the device
- The ordinary app business model: free with ads, and one small purchase, priced by region through Google Play, removes them, with nothing else held back behind it
Result
On Google Play, free with ads, with no account and no server. Everything a user enters stays on their phone, which is also why the whole app works with no connection.