Site welfare and safety loads usually come online first, followed by lighting and security, communications and monitoring, support loads for tracker and inverter testing, and finally test equipment and tools. That order is a starting point, because sequencing depends on the project, the equipment vendor and the utility. A generator does not energize the array and does not replace the utility interconnection, so its job is to carry the supporting loads around that work. This guide ranks those loads by priority so a diesel generator can be sized, staged and shed in an order the whole crew can follow.
Temporary power also carries a safety layer. OSHA’s 1926.404 standard has employers choose between ground-fault circuit interrupters and an assured equipment grounding conductor program for covered temporary receptacle outlets and cord-and-plug equipment in use by employees. Your safety lead and electrical contractor decide which method applies to each circuit. Settle that question before the first tool is plugged in.
Why Load Order Matters on a Generator
A generator carries what it is given, so the order in which loads are added changes how much margin the unit has at any moment. Starting a large motor load while many smaller loads are already running can stress a unit, and the exact figures come from equipment data supplied by your vendor. Adding loads one tier at a time also makes faults easier to trace, since a new problem points to the circuit that was just connected. The construction site generator sizing and load list guide explains how to build the list that feeds this ranking.
Priority Tiers at a Glance
The table below groups typical commissioning-stage loads into six tiers. The tiers are a planning pattern, not a prescribed procedure, so move items up or down to match your project documents. Tier 1 is the first to be energized and the last to be shed, while Tier 6 is the last to be added and the first to be dropped when capacity runs short. Use it as a draft for the conversation among the commissioning manager, the electrical contractor and the rental provider.
| Tier | Typical loads | Why it ranks here | Shed order |
|---|---|---|---|
| 1. Welfare and safety | Site offices, welfare trailers, emergency and egress lighting | People depend on these spaces every day | Shed last |
| 2. Lighting and security | Work-area lighting, gate controls, cameras, alarms | Crews need visibility and a secured perimeter | Shed late |
| 3. Communications and monitoring | Network equipment, data loggers, monitoring panels | Teams coordinate with the vendor and utility through these links | Shed late |
| 4. Tracker and inverter testing support | Auxiliary and control power the vendor specifies | Requirements come from the vendor, owner and utility | Shed only on their instruction |
| 5. Test equipment | Meters, test sets, laptops and chargers | Needed on the schedule the test plan sets | Shed before Tier 4 |
| 6. Tools and general loads | Power tools, compressors, pumps, welders | Easiest to reschedule | Shed first |
What Sits in the Early Tiers
Welfare and safety loads rank first because people occupy those spaces daily, and losing them stops work for reasons unrelated to commissioning. Lighting and security follow, since commissioning work often runs around energized equipment and crews need visibility and a secured perimeter. Communications and monitoring come next, because teams typically need data links to coordinate with the vendor and utility, although the exact equipment varies by project. These early tiers are often modest in demand compared with later work, which makes them good candidates for a steady base load on the generator.
Support Loads for Tracker and Inverter Testing
This is the tier where project documents matter more than rules of thumb. The equipment vendor sets the auxiliary or control power a given tracker or inverter needs during testing, and the utility and owner set what must be in place before any energization step proceeds. Ask the electrical contractor for those requirements in writing, and add them to the load list as their own line instead of folding them into general site demand. Starting characteristics and duty vary by equipment, so give the rental provider the vendor’s data rather than an estimate.
Test Equipment and Tools
Test equipment and hand tools sit near the bottom of the ladder because they are the easiest loads to reschedule. Many electronic instruments are sensitive to power quality, so ask the manufacturer what supply they expect and keep them on a feeder separate from motor starts. Compressors, pumps and welders belong on their own feeder so they can be shed first.
A Numbered Order for Staging Loads
The list below turns the tiers into a working sequence for one generator. It is a planning pattern, not a commissioning procedure, and it should be adjusted to the vendor’s instructions and the contractor’s plan. Each step assumes the previous tier is running steadily before the next one is added.
- Build the load list with every item labeled by tier and with vendor requirements attached.
- Energize Tier 1 and Tier 2 loads first and confirm they run steadily.
- Add Tier 3 communications and monitoring and confirm the links work.
- Bring on Tier 4 support loads only when the electrical contractor and vendor call for them.
- Add Tier 5 test equipment on its own protected feeder.
- Connect Tier 6 tools last, and be ready to shed them first when capacity is tight.
- Record the final load picture so the next phase starts from known numbers.
Staging Distribution
Distribution is where the tier plan becomes physical. Splitting feeders by tier lets the crew isolate tools without disturbing offices, lighting or data equipment. Stag’s power distribution equipment is the place to start when planning panels, cabling and branch circuits for a spread-out site. Ground-fault protection for temporary circuits should be settled at this stage, as noted earlier.
When one generator cannot carry the combined tiers, paralleling generators for scalable power describes how multiple units can be combined. Stag’s fleet runs from 20 kW to 2000 kW, which gives room to match unit size to the tiers. Whether to use one larger unit or several smaller ones depends on the load list, the site layout and fuel logistics. For the fuel side of a spread-out site, see the article on remote solar site fuel delivery.
What Changes When Permanent or Grid Power Arrives
When permanent or grid power arrives, the load picture shifts and some temporary loads move to the permanent supply. Which loads transfer, and when, depends on the utility, the interconnection agreement and the owner’s commissioning plan, so treat any schedule as something to confirm. Do not retire the generator until the electrical contractor confirms the permanent supply covers what the generator was carrying. A transfer switch can keep a diesel unit in place as a backup path for critical loads if the project calls for one.
The generator never connected the array to the grid. Interconnection and energization remain utility and owner activities, and the temporary power plan should follow the schedule they set. Review the load list at each change, and see the solar farm commissioning generator guide for broader context on temporary power at these sites. For what happens when that date slips, see the article on late interconnection delays on a solar project.
Putting the Load Order to Work With Stag
Stag Power Rentals supplies diesel generators from its Dickinson, TX yard, with a fleet from 20 kW to 2000 kW, and rentals are billed by single, double or triple shift. Shift billing can be matched to how long each tier runs on your site, so tell the team which loads run around the clock and which follow day crews. Bring your tier list, vendor requirements and expected sequence, and the team can help match units to them. Read the construction industry overview for how Stag supports jobsites, then send your list through the quote form.
Frequently Asked Questions
What loads should a generator carry first during solar commissioning?
Welfare and safety loads such as site offices and emergency lighting usually come first, followed by lighting and security and then communications and monitoring. Tracker and inverter support loads, test equipment and tools follow in that order. The exact sequence depends on the project, the equipment vendor and the utility. Confirm it with your electrical contractor before building the load list.
Can a generator energize a solar array?
No. A generator supports the loads around the array, such as offices, lighting, communications and test equipment. Energizing the array and connecting it to the grid are steps controlled by the utility, the owner and the equipment vendor. Your commissioning plan defines how those steps are carried out.
How do I decide what to shed first when capacity runs short?
Shed in reverse order of the tiers, starting with general tools, compressors and pumps. Test equipment comes next, while communications, lighting and welfare loads stay on the longest. Tracker and inverter support loads should be dropped only on instruction from the vendor or electrical contractor. Writing the shed order into the load list before work starts avoids guesswork on site.
Should tracker and inverter support loads share a feeder with site offices?
That depends on the vendor’s requirements and the electrical contractor’s design. Many crews prefer separate feeders so that a tool trip does not interrupt offices or data links. Separate feeders also make it simpler to isolate a problem circuit. Ask the vendor whether any power quality requirements affect how those loads are fed.
Do I still need the generator after grid power arrives?
That depends on the utility, the interconnection schedule and what the permanent supply covers. Some projects keep temporary units in place until the electrical contractor confirms permanent power carries every load the generator served. Others retain a diesel unit as a backup behind a transfer switch. Review the load list at each stage and confirm the plan with the owner before releasing equipment.