Rooftop solar
Turn electricity use into PV capacity, panel count and an indicative roof requirement.
India calculator ↗Dollar-based calculator ↗INDEPENDENT ENERGY PLANNING
Better energy decisions
start with clear numbers.
Work out your solar size, battery capacity or charging needs. Understand the assumptions behind every estimate.
Free to use · No sign-up · Calculations in your browser
THE TOOLKIT
What are you planning?
Start with a question.
Leave with a result you can explain.
Battery sizing
Separate power from energy. Check usable capacity, topology and the voltage window.
Size a battery ↗Start with essential loads ↗Battery dispatch
Test a charge/discharge schedule against a load profile and state-of-charge limits.
Test a schedule ↗Understand energy limits ↗EV charging
Check charging time, connection windows, site power and retail energy cost.
Plan EV charging ↗Will it be ready by morning? ↗FIELD GUIDES
Go beyond the headline number.
Solar · 7 min
Size solar from energy use, not your bill total.
Work from 12 months of kWh, check solar yield, round to whole panels, and test a lower-generation case.
Read the field guide Solar · 6 minWhy 100% solar generation is not a zero bill.
Compare daytime use and exports with an explicit energy balance, and avoid overstating solar bill savings.
Read the field guide Battery storage · 7 minSize backup for the loads you actually need.
A reproducible critical-load example that separates battery energy, inverter power, reserve and ageing.
Read the field guide Battery storage · 6 minA battery can have enough energy and the wrong voltage.
Use a 469-cell example to check the full voltage range, series and parallel topology, and PCS compatibility.
Read the field guide Dispatch · 6 minWhen a battery schedule asks for more than it can deliver.
Follow a one-hour SOC calculation, check the energy balance and understand clipped battery dispatch.
Read the field guide EV charging · 6 minWill your EV be ready by morning?
Translate driving into wall energy and test vehicle, charger, site-power and connection-window constraints.
Read the field guideYOUR PLANNING NOTEBOOK
One assumption can
change the answer.
Try a lower solar yield. Allow for an ageing battery. Check a shorter charging window. Save the cases side by side and take the inputs with you.
Compare your scenarios ↗Same 2.75 kWp solar arrayIllustrative annual output
4 sun hours/day3,132 kWh
5 sun hours/day3,915 kWh
6 sun hours/day4,698 kWh
78% performance ratio · generation, not bill savings
METHODS THAT YOU CAN INSPECT
Useful tools need clear boundaries.
Worked examples distinguish assumed inputs from measured data. Guides explain model limits. Changes are recorded when the content or calculation actually changes.
Read our methods and source notes ↗New: field guides & planning notebook
Six calculation notes, transparent scenario comparisons and links between each guide and its tool.
Read the change log ↗