Size temporary solar power for construction sites from the loads it must serve, when they run and how the system will recharge. Check daily energy, simultaneous power, starting demand, seasonal solar yield and the battery reserve window separately. These checks turn a general request for “site power” into a project brief that suppliers can assess.
Solar can support temporary offices, welfare facilities, lighting, communications and tool charging. Large motors, heating and electric plant charging need their own assessment. If the equipment format is still undecided, compare fold-out solar arrays, solar trailers and solar containers alongside the sizing work below.
Define the Project Power Scope
Start with a boundary: the whole site, one compound or selected circuits. Record the location, operating months, shift pattern and expected project phases. Identify loads that must continue during poor weather, equipment faults or quiet hours, and those that can be delayed or supplied separately.
Arrangement | Planning requirement |
|---|---|
Direct solar for flexible daytime tasks | Loads and controls must tolerate changing solar output and agreed interruptions |
Solar plus battery storage | PV production, load timing, battery power and stored energy must work together |
Hybrid solar, battery and generator or grid supply | Confirm input limits, control responsibilities, charging capacity and backup availability |
Suppliers may describe integrated packages as solar generators, portable power stations or mobile BESS. Confirm the included components and ratings when comparing these labels.
A solar array’s kWp DC, an inverter’s kW or kVA AC, and a battery’s kWh describe different capabilities. Keep all three in the specification. Aggreko’s temporary construction power guide also highlights starting loads, project growth and distribution equipment as separate planning inputs.
Build a Construction Site Load Schedule
List each load group, its electrical input, quantity, operating hours and expected duty cycle. Record voltage, frequency, phase and any starting requirement alongside the energy calculation. Measurements from a representative work period give a stronger basis than assumed tool ratings alone.
For a load with a known running draw:
Daily energy (kWh) = aggregate running power (kW) × scheduled hours × running fraction
If the input is already an average over the scheduled period, multiply by time only. Applying another duty-cycle reduction would undercount consumption. For tool-battery charging, use the charger’s AC input energy or measured input profile; an equipment battery’s nominal capacity alone does not establish the charging load.
Worked Example: A Small Construction Compound
The following values are illustrative assumptions, not a measured project or Hinergy equipment specifications. They cover office and auxiliary loads; larger electric plant, welding and other unlisted equipment are outside this example. Each power value is the aggregate draw for its load group, so quantity is already included.
Load group | Running draw | Scheduled hours/day | Running fraction | Daily energy |
|---|---|---|---|---|
Office electronics and communications | 0.60 kW | 10 h | 100% | 6.0 kWh |
LED work lighting | 0.40 kW | 10 h | 100% | 4.0 kWh |
Tool-battery charging | 1.00 kW | 3 h | 100% | 3.0 kWh |
Small pump | 1.50 kW | 2 h | 100% | 3.0 kWh |
Security and network equipment | 0.05 kW | 24 h | 100% | 1.2 kWh |
Cabin HVAC | 1.60 kW | 6 h | 50% | 4.8 kWh |
Total energy delivered to listed loads | — | — | — | 22.0 kWh/day |
Record energy by hour as well as by day. The same 22 kWh can create different storage and inverter requirements depending on when it is used. Include standby consumption, battery cooling, controls and other auxiliaries in the final model. Naman Systems’ construction battery guide provides another example of separating a load schedule from the power and recharge checks.
Check Simultaneous Power and Starting Demand
Map which loads can run together. If every group in the example is running at its listed draw, the steady total is 5.15 kW. The HVAC’s 50% daily running fraction reduces its energy contribution; it does not halve the power required while the compressor is on.
This steady sum is a starting input for the electrical review. Confirm:
Continuous output at the expected ambient temperature and operating conditions.
Motor starting kVA or current, starting method, duration and overlap with other loads.
Power factor, phase balance and the limits of each output and connection.
Battery discharge capability, inverter overload behavior and supported hybrid operation.
Energy monitoring intervals can reveal daily demand patterns, but brief motor-starting events require suitable measurements or manufacturer data. Avoid choosing an inverter from a generic surge multiplier. Caterpillar’s mobile BESS white paper explains why power, stored energy and input or pass-through limits need separate checks.
Size PV for the Operating Season
Use the actual coordinates, project months, array orientation, shading and expected surface conditions. Cranes, scaffolding, cabins and stockpiles can change solar access as work progresses. DEUTZ’s construction BESS guide highlights these site-dependent renewable inputs.
A preliminary solar-energy calculation is:
PV capacity (kWp DC) = target daily solar-served energy (kWh AC/day) ÷ modeled net usable yield (kWh AC per kWp DC/day)
The yield must match the energy boundary. Specify whether it includes PV conversion losses, the share passing through storage and the associated losses. Avoid applying the same loss allowance twice. Peak sun hours describe equivalent solar irradiation; they are not the hours a site is open or simply the time between sunrise and sunset.
For the example, assume a net usable yield of 3.0 kWh AC per kWp DC per day, after the modeled direct and stored energy paths. This is an arithmetic input, not a location-based forecast:
22.0 ÷ 3.0 = 7.33 kWp DC
About 7.3 kWp therefore passes this simplified average daily energy screen. It does not establish continuous supply through cloudy periods. If another 8.0 kWh of AC-equivalent reserve restoration must be achieved on a recovery day, the same assumed yield gives:
(22.0 + 8.0) ÷ 3.0 = 10.0 kWp DC
The project model must test the actual recovery period and weather sequence. JRC’s PVGIS off-grid method simulates changing demand, generation and battery energy, and reports missing energy and battery depletion. This captures information an average-day comparison cannot provide.
Size Battery Storage for a Defined Reserve Window
Define when the battery must supply loads without replenishment and which loads remain connected. In this example, assume the hourly schedule allocates 8.0 kWh AC of the daily demand to a selected reserve window. That is part of the 22.0 kWh daily total, not an additional daily load.
For an initial calculation from nominal DC capacity:
Nominal battery energy (kWh DC) = required load energy (kWh AC) ÷ (usable SOC fraction × DC-to-AC delivery efficiency)
Assume an 80% usable state-of-charge window and 92% delivery efficiency solely for this example:
8.0 ÷ (0.80 × 0.92) = 10.87 kWh DC
This gives approximately 10.9 kWh nominal DC before further allowances for temperature, aging, auxiliary demand and the project’s contingency policy. Confirm the battery can also deliver the required power during that window.
Ask what a supplier means by “usable capacity.” If usable AC energy is already specified at the required conditions, compare it directly with the AC load requirement. If usable DC energy is given, apply only the remaining delivery losses. Do not reduce an already usable rating by the same SOC allowance again.
Check Recharge Time and Backup
A battery needs a repeatable energy source between operating windows. Check solar, grid or generator availability against concurrent site loads, charger limits, battery acceptance, temperature and the available charging period. United Rentals’ equipment charging guide emphasizes that the charger and the receiving machine can each limit charging speed.
For the example’s 8.0 kWh AC discharge, the corresponding DC energy withdrawn is:
8.0 ÷ 0.92 = 8.70 kWh DC
If net power retained in the battery is assumed constant at 2.0 kW, the energy-only recharge estimate is:
8.70 ÷ 2.0 = 4.35 hours
Net charging power here is after live-load demand and charging losses. The actual time must allow for changing solar output, charging taper and other limits. A generator’s or grid connection’s full rating cannot be assigned to charging while the same source also serves the site.
Set the Backup and Recovery Rules
Specify the protected load group, minimum reserve, backup trigger, permitted generator operating periods and recovery target. Identify who responds if charging is unavailable or demand exceeds the plan. Where supported, scheduling tool charging during solar production can reduce the energy that must be shifted through storage.
For hybrid solar diesel power, evaluate fuel consumption against measured load and charging behavior. Fewer engine hours do not guarantee a proportional fuel saving. Power Electrics discusses this sizing issue, together with quiet overnight loads and limited grid capacity.
Put the Results into a Project Sizing Brief
Keep the assumptions together so suppliers can compare the same requirement. For the illustrative compound, the load is 22.0 kWh/day, the all-running steady sum is 5.15 kW, and the selected reserve window is 8.0 kWh AC. The solar and nominal battery figures above are energy-screening results that still require an electrical and chronological operating model.
Information to send | What the project team should specify |
|---|---|
Load schedule | Running input, hours, duty cycle, measured energy and concurrent operation |
Electrical requirements | Voltage, frequency, phase, power factor and starting events |
Site and dates | Coordinates, project months, shading, temperatures and project stages |
Reserve requirement | Protected loads, duration, usable-energy definition and contingency policy |
Recharge and backup | Available sources, net charging window, input limits and recovery target |
Equipment scope | PV array, inverter, battery, controls, cables, protection and distribution |
Deployment | Site drawing, handling equipment, storage position and collection route |
Acceptance | Required documentation, commissioning responsibilities and operating checks |
A Mobile Fold-Out Solar Array System can form the PV part of a temporary solar power system. Confirm the supplied array, base, folding mechanism and connection components, then identify which inverter, battery and distribution items are included or supplied separately. Use our mobile solar array deployment and stowage guide to prepare the handling and site-layout information.
The responsible electrical team should confirm the complete design, protection, grounding or bonding, distribution and applicable site requirements before operation. For U.S. construction projects, OSHA 1926.404 is one relevant reference; local and project-specific requirements also need review.
Frequently Asked Questions
Can solar power run an entire construction site?
It depends on the loads, solar resource, storage, backup and interruption tolerance. Start with a defined load group, then check each project phase. Large motors, electric plant charging and extended heating can change the scale substantially.
How many solar panels does a construction site need?
Determine the required DC array capacity from the modeled energy contribution and site conditions, then select a compatible module and array configuration. Panel count follows that design. Nominal panel wattage alone does not establish daily output or reliable site power.
Should the battery store one full day of site energy?
Size it for the operating strategy. A night reserve, a planned generator-off interval and a full day without replenishment are different requirements. State the protected loads and duration, then compare usable energy and output power under the required conditions.
What happens during several cloudy days?
Model the weather sequence, remaining reserve and recovery time. A grid or generator input, reduced noncritical demand or another agreed source may be needed. A larger array helps only within the available space, electrical limits and actual solar conditions.
Can the same system be used on the next project?
Recheck the next site’s loads, season, phase and voltage requirements, charging sources and deployment conditions. A portable format supports relocation, but the power and energy assessment should be repeated when the operating conditions change.
Request a Construction Site Power Review
Send Hinergy your load schedule, site coordinates, operating months, shift pattern, reserve requirement and available charging sources. Include the site plan and any existing inverter, battery or generator details. These inputs help define the PV array requirement, integration questions and quotation scope for your temporary construction project.