Matching solar to your load profile

A solar system generates power on its own schedule — strongest around midday, nothing at night, less on cloudy days and in the monsoon. A factory consumes power on its schedule — shifts, machines starting and stopping, weekends, holidays. The value of on-site solar depends on how well these two schedules overlap. That's why understanding your load profile is the starting point for sizing a solar system.

What a load profile is

A load profile shows how consumption varies over time:

• Daily — hour by hour through a typical day
• Weekly — weekdays vs weekends
• Seasonal — through the year
• Exceptional — holidays, maintenance shutdowns

The best data comes from interval meter readings (every 15 or 30 minutes) over a full year. Monthly bills give only totals. See reading your industrial electricity bill.

Key concepts

Self-consumption

The share of solar generation consumed on site at the time it is produced. High self-consumption usually means high value per unit, because each unit displaces grid purchases.

Solar fraction

The share of the facility's total consumption met by solar.

Surplus

Generation exceeding on-site consumption at that moment. What happens to surplus depends on the metering and export arrangement — it may be exported for credit, valued at a lower rate, or curtailed. See net metering vs gross metering.

Typical profiles

The sizing trade-off

• Small system — nearly all generation self-consumed, high value per unit, but smaller total savings
• Larger system — more total generation, but increasing share of surplus, possibly at lower value
• Oversized system — substantial surplus, value depends heavily on export rules

The optimal size balances total savings against the value of surplus, within regulatory limits on system size for your connection.

Regulatory limits

Rooftop and on-site system capacity may be limited by sanctioned load, contracted demand, transformer capacity or regulations. Check current rules with the distribution company and the state regulator.

Shift patterns and closures

Count how many days per year the facility is closed or running at low load — Sundays, holidays, maintenance shutdowns. On those days, solar output may largely become surplus. A system sized to weekday load may generate significant surplus on weekends.

Seasonal effects

Both solar generation and consumption change with seasons:

• Solar is typically stronger in clear, dry months and weaker in the monsoon
• Cooling loads rise in hot months
• Production schedules may be seasonal

A month-by-month comparison reveals whether solar and load are aligned through the year.

Improving the match

Load shifting

Moving flexible loads — pumping, batch processes, charging, pre-cooling — into solar hours increases self-consumption.

Storage

Batteries can store midday surplus for evening use, though they add cost. See battery storage for industrial sites.

Orientation

East-west orientation spreads generation across the day, with a flatter profile than south-facing arrays. This can better match some loads.

Off-site supply

If on-site solar can't meet your goals, combine it with off-site renewable supply. See open access vs group captive.

A sizing process

1. Gather a year of interval consumption data
2. Model solar generation for the site, hour by hour
3. Overlay generation on load to calculate self-consumption and surplus at different sizes
4. Value self-consumed energy and surplus under current rules
5. Check regulatory size limits
6. Compare options on savings and investment
7. Choose a size, and plan for future load changes

Planning for change

Facilities change. New production lines, electrification of processes or closing shifts all change the load. Consider:

• Is load expected to grow or shrink?
• Can the system be expanded later?
• How will surplus be handled if load falls?

Common mistakes

• Sizing to annual consumption without checking hourly match
• Ignoring weekend and holiday surplus
• Using monthly bills instead of interval data
• Assuming surplus will always be credited at full value
• Not checking regulatory size limits

An illustrative comparison

Imagine, purely for illustration, two factories with the same annual consumption. The first runs a single day shift six days a week; the second runs continuously. The same solar system on each would perform very differently: at the first, midday generation would often exceed load on Sundays and holidays, creating surplus; at the second, almost every unit would be consumed on site, but solar would cover only a modest share of total consumption. Same annual numbers, different answers — which is why the hourly profile matters more than the total.

How we help

Through our C&I solar work with industrial consumers, we help analyse load profiles, model self-consumption at different system sizes and coordinate EPC partners to design systems that match how facilities actually use power.