Power for your needs.
Choose how you’d like to use the calculator.
End-User: a simple estimate for your home or business.
Installer: detailed inputs and sizing assumptions.
Tell us what you need.
No technical knowledge needed. A few details will help us get started.
What would you like to run?
Choose appliances, quantities and hours of use. Tick the ones you want to keep on during an outage.
Suggested watts are examples. If you know the wattage on an appliance label, you can change it below.
Your solar starting point.
Here’s an estimate based on your appliances and selected backup time.
Detailed solar sizing
Enter load characteristics and review sizing assumptions for a preliminary engineering estimate.
Verify equipment limits, site conditions and compatibility before final selection.
Your project
Your appliances
Use electrical input watts from the appliance label. Reference values are examples; replace them with your actual ratings.
Duty (%) is the portion of operating time an appliance actively consumes its running power. Simultaneous use (%) affects peak power, not daily energy.
3 · Review sizing assumptions
These starting values are estimates, not weather data for your site. Confirm with BEECROFT before selecting equipment.
Depth of discharge, discharge efficiency and retention apply to nominal DC battery kWh. PV yield factor excludes inverter and battery losses, which are applied separately. No bifacial energy bonus is assumed.
How the estimate works
Daily energy = quantity × electrical input kW × operating hours × duty factor. If measured daily kWh per appliance is entered, it replaces the hours-based energy estimate.
Inverter continuous kW and kVA use simultaneous loads, growth and headroom. Starting demand adds the largest grouped starting increment to the running kVA. A blank group assumes independent starts; matching groups assume simultaneous starts. Phase results assume three-phase appliances are balanced.
Battery nominal kWh = backup AC energy ÷ (depth of discharge × capacity retention × discharge efficiency × inverter efficiency). Off-grid battery energy also covers the full entered night load, if larger. Module counts are rounded up by energy only; discharge power and compatibility still need checking.
Hybrid/off-grid PV kWp = [day AC kWh ÷ inverter efficiency + night AC kWh ÷ (inverter efficiency × battery round-trip efficiency)] ÷ (peak sun hours × PV yield factor), then PV headroom is applied. This assumes night energy is cycled through the battery. Separate autonomy recovery and charger sizing are not included.
Grid-tied PV kWp = annual load kWh × target generation coverage ÷ annual specific AC yield. Grid inverter AC kW = rounded PV kWp ÷ DC/AC ratio. Direct consumption is only an annual ceiling limited by daylight energy; actual export or curtailment requires hourly modelling.
Protection, cable sizes, string layout, utility approvals, thermal refrigeration design, tariffs and quotations are handled by the engineering team.
Supporting references: PVWatts solar modelling · Manufacturer kW / VA ratings