A monthly electricity bill cannot show whether solar will meet a facility’s real daytime demand, because it hides the timing of peaks, shutdowns, cloudy periods and process changes. By comparing interval data with modeled solar output, you can choose an array size, operating strategy and system architecture that reduce purchased power without paying for generation the site cannot use.
Key takeaways
- Compare interval demand with simulated PV output before selecting capacity.
- Size the system against peak and daytime demand, not annual kWh alone.
- Match solar generation with shifts, motors, cooling, and other operating loads.
- Verify roof capacity, grid limits, protection settings, and installer calculations.
Start with the facility’s 15-minute or 30-minute load profile
Compare a 15-minute load profile with simulated PV output before choosing system capacity. If only 30-minute interval data is available, use it to map the facility’s kW or kVA demand through each day, not just the monthly electricity bill.
| Data source | What to examine | Why it matters |
|---|---|---|
| Annual electricity bill | Total kWh and billing demand | Two facilities can use the same annual energy but have different solar suitability. |
| Interval meter data | Demand during each 15- or 30-minute period | Reveals operating shifts, short peaks and the minimum daytime load. |
| Solar-hour overlap | Load between expected sunrise and sunset generation hours | Shows how much PV the facility can consume directly. |
| Seasonal records | Daytime demand during summer, winter and monsoon | Prevents a design based on one unusually productive or busy period. |
A strong match exists when the facility’s daytime electricity demand remains above expected PV output for much of its operating schedule. That pattern supports high solar self-consumption because the inverter supplies onsite loads first, reducing imported units before any surplus is exported or curtailed.
Do not treat solar generation as a guaranteed solution for maximum-demand charges. A brief motor start, cloudy interval or night shift can still create the billing peak, even when solar substantially lowers daytime kWh purchases. Mark the highest 15-minute or 30-minute demand separately from the daily energy total; capacity decisions need both figures.
Size solar against demand, not annual kWh alone
An industrial array is correctly sized when its simulated output serves the daytime load without regularly exceeding on-site consumption, inverter capacity or the permitted export limit. Annual kWh alone misleads: two facilities can use the same yearly energy while having different daytime loads, peak demand periods and solar self-consumption.
Use PV production modeling with hourly or sub-hourly weather data, module temperature coefficients and the roof’s mounting configuration. Compare that output with the interval meter profile, then set boundaries for:
- Minimum daytime load: the lowest load the array must serve before excess generation appears.
- Peak demand: the facility’s highest kW and kVA requirement, including short intervals that can affect demand charges.
- Sanctioned load: the utility-approved limit, which solar does not automatically increase or replace.
- Seasonal output: hot modules, monsoon clouds and winter sun alter the power available at the same hour.
- Inverter capacity and export limit: extra DC panels can improve morning and afternoon production but create clipping at the AC limit.
Treat kWh versus kW and kVA as different design questions. Solar reduces purchased kWh, but a brief non-solar load can still establish the billing peak. If storage is proposed, size its power in kW for peak shaving and its energy in kWh for the required duration; charging and discharging losses reduce usable energy.
Choose more panels only when the modeled gain outweighs clipping, exports and unused capacity.
Match generation to the way the facility operates
A facility with a constant base load can use solar directly through much of the day, while a site that runs mainly at night gains less from the same array. Compare interval demand with simulated solar output across operating days, not just annual kWh.
1. Mark the hours when demand is highest. Schedule shiftable loads such as pumping, refrigeration, compressed-air production and water heating into strong solar hours only when product quality, process constraints and restart requirements allow it.
2. Separate batch processes from steady demand. A batch started during a solar peak can consume more onsite generation than a process that finishes before noon, but moving it may increase labour, cooling or restart costs. A short cloudy interval can also leave the utility supplying the batch.
3. Model the monsoon separately from the dry season. Cloud cover reduces production, while high module temperature on a hot industrial roof reduces instantaneous output against the panel rating. Check whether the facility still has enough daytime supply during the months when solar output is weakest.
4. Use a battery for a defined mismatch, not as a substitute for sensible panel sizing. Battery power in kW determines how much demand it can shave; energy in kWh determines how long it can sustain that output.
Include charging and discharging losses, and size both against the billing peak or evening load you want to address.
5. Confirm the export rule before accepting surplus generation. If onsite demand falls below PV output, the inverter must export or curtail power under the interconnection agreement. Solar can reduce purchased units without removing a short maximum-demand interval, so test the design against the facility’s actual billing peak.
Choose the electrical architecture and confirm the grid limits
A behind-the-meter solar array within a grid-connected system is usually the practical arrangement for a high-demand facility: solar serves onsite loads first, while the utility supplies any shortfall. It does not guarantee uninterrupted operation; anti-islanding protection shuts down a standard inverter during a grid outage.
| Arrangement | Supply during normal operation | Outage capability | Suitable use |
|---|---|---|---|
| Grid-connected system | Solar plus utility power | Solar stops when the grid fails | Lowering imported energy and daytime demand |
| Hybrid solar | Solar, battery and utility power | Critical loads continue through an islanding controller | Facilities requiring backup for selected equipment |
| Off-grid system | Solar, batteries and another dispatchable source | Independent of the utility | Sites without reliable grid access |
Before interconnection, obtain written confirmation of:
- The sanctioned load, contract demand, service voltage, phase arrangement and transformer capacity.
- The utility’s application, protection and metering requirements, including net-metering or export limits.
- Whether reverse power flow is permitted; export-limited projects need a power-control meter and inverter curtailment settings.
- Anti-islanding, earthing, overcurrent, surge-protection and automatic-disconnection settings.
- The point of common coupling, short-circuit level and utility-approved single-line diagram.
Keep the facility’s demand charge in view. A brief non-solar peak can still set the billing maximum, even when solar sharply reduces daytime units.
Check the roof, controls and installer’s design evidence
Approve the installation only when the drawings, calculations and control logic show how the system will perform on your roof and against your actual daytime load.
1. Request a stamped roof assessment confirming roof structural capacity for modules, racking, ballast, wind uplift and any local snow load. Check roof penetrations, drainage routes, maintenance walkways, fire setbacks and the remaining waterproofing warranty. A roof that passes today still creates a replacement problem if its membrane expires before the PV system.
2. Review the production model, not just the annual kWh forecast. It should show hourly or 15-minute output, panel orientation, inverter losses, high-temperature derating and monsoon conditions. Compare those results with interval meter data to expose clipping, weak afternoon production or insufficient output during your critical process hours.
3. Ask for the proposed DC-to-AC ratio and the clipping calculation. More panel capacity can improve morning and cloudy-period inverter utilisation, but excessive oversizing wastes module output when the inverter reaches its AC limit. The chosen ratio must fit your tariff, load shape and sanctioned connection capacity.
4. Test the control sequence in writing: on-site loads first, then battery charging or export, with curtailment when required. Confirm the export limitation setpoint, response time, anti-islanding protection, monitoring alarms and what happens during a utility outage.
Ask Ms365 Solar Solution to include these items in the solar installation design review, alongside single-line diagrams, equipment datasheets and commissioning test records.
Related products
 | Industrial power solar system Industrial power solar system View product → |
 | commercial power solar system commercial power solar system View product → |
Frequently asked questions
What load data should you collect before sizing industrial solar?
Collect 15-minute interval data when available. Use 30-minute data to map daily kW or kVA demand rather than relying only on monthly bills.
Why should industrial solar be sized against demand instead of annual energy use?
Annual kWh can hide short, high-demand periods. Compare the facility’s interval demand with simulated PV output to assess how much solar supports daytime loads.
How should solar generation be matched to facility operations?
Compare PV output with operating shifts, production schedules, motors, cooling systems, pumps, and other daytime loads.
What must be checked before approving an industrial solar design?
Check roof condition and load capacity, electrical architecture, inverter and protection settings, grid export limits, controls, and the installer’s design calculations.
Related product
 | Solar Panel System Solar Panel System in Nagpur View product → |
