Calculating what is required.
WHAT TO CALCULATE IN ORDER
Daily energy requirement, from the load assessment Battery capacity needed for the required autonomy Generation capacity needed to replace what is used Inverter capacity for the simultaneous load and surge
WHAT AUTONOMY MEANS
How long the system supplies load without generation.
WHAT TO ESTABLISH
How many days of poor generation the customer needs to survive.
WHY IT MATTERS HERE
Cloudy periods reduce generation substantially and systems sized for perfect days fail.
WHAT TO ACCOUNT FOR IN BATTERY SIZING
Usable capacity, which is less than nominal Depth of discharge limits Efficiency losses Degradation over life
WHY DEPTH OF DISCHARGE
Discharging batteries deeply shortens their life dramatically.
WHAT TO ACCOUNT FOR IN GENERATION SIZING
Realistic sun hours for the location Temperature derating Shading and dirt losses System efficiency losses
WHAT SUN HOURS TO USE
Conservative figures for the worst season, not annual averages.
WHY
Systems must work in the worst month, not the average one.
WHAT TO ACCOUNT FOR IN INVERTER SIZING
Total simultaneous load Starting surge of the largest motor Headroom
WHAT TO ADD OVERALL
Margin.
WHY
Every assumption is optimistic, and losses compound.
WHAT UNDERSIZING PRODUCES
Systems that fail during normal use, damaged batteries, and a customer who tells everyone.
WHAT OVERSIZING PRODUCES
A price the customer will not pay.
WHAT TO PRESENT
The calculation, so the customer understands what they are buying.
