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An off-grid industrial site is not a small version of a grid-tied commercial plant. There is no mains to fall back on, so the design has to hold through the worst hour of the worst week, and the business case is usually measured in generator hours and fuel deliveries rather than in kilowatt-hours.
This page is for operators and EPCs specifying power for remote industrial loads — mining, quarrying, construction camps, remote processing, agriculture at scale — where a generator is currently doing the work. It covers what has to be known before anything can be sized, and where the money is actually saved.
The load profile is the design input
Everything follows from the load profile, and it has to be a profile rather than a single number. Three things matter: the average, the peak, and how quickly the load changes. A site with a flat 200 kW load and a site with a 200 kW average that spikes to 600 kW for ten seconds when a crusher starts need very different inverter capacity and very different storage.
The shift pattern matters as much as the total. A camp that is busy in the evening and quiet during the day has a generation profile that does not line up with its consumption, and that mismatch is what storage is for. Getting the profile right is the difference between a system that works and one that needs a bigger generator than the one it replaced.
Size against the generator, not against the average
The usual commercial question is not “how much of the load can solar cover” but “how many generator hours can we remove”. Those are different objectives. Designing to maximise solar fraction tends to over-size the array for the hours that are easy and leaves the generator doing the expensive peak work. Designing to remove generator hours targets the array and the storage at the hours the generator is actually running.
The generator is commonly retained. Any change in its rating requires a review of the worst-case load, motor starting, charging demand and required reserve. Removing it entirely is possible on some duty cycles, but it moves the whole risk onto the array and storage, and it is worth being explicit about what that risk costs before choosing it.
Autonomy is an hours question, not a days question
Autonomy — how long the site runs on battery without sun or generator — is the number that drives storage cost. A few hours of storage may cover short interruptions or an evening peak if the load study supports it. Two or three days of storage does not guarantee a week of operation; longer autonomy requires site-specific weather, load and reserve modelling. The second is a different project, and the cost difference is large enough that it should be a deliberate decision rather than a default in either direction.
The usual answer on industrial sites is a few hours of autonomy plus a retained generator: the battery handles the daily cycling and the peaks, the generator handles the rare long bad-weather stretch. That combination removes most of the fuel without buying capacity that sits idle most of the year.
Surge and motor starting decide the inverter size
Motor starting current is several times running current, and inverters have a surge rating with a duration attached. A 200 kW site with a large motor that starts loaded can need inverter capacity well above 200 kW, or a soft starter on the motor, or both. This is the single most common reason an off-grid system trips on day one.
The fix is cheap at design stage — a soft starter, or sequencing so two motors never start together — and expensive afterwards. It is worth listing every motor above a few kilowatts before the inverter is selected.
Heat, dust and salt are the real environmental inputs
Remote industrial sites are usually hot, dusty, and sometimes coastal. All three act on the equipment continuously:
- Heat shortens battery life and derates inverters. Ambient design temperature should come from the site, and the enclosure needs ventilation or cooling sized to it.
- Dust blocks filters, reduces module output and gets into enclosures. Filter maintenance is a scheduled item, not an occasional one.
- Salt drives corrosion class on everything metal, from the racking to the enclosure finish. Distance from the coast and wind direction set the specification.
Fuel logistics is where the saving actually is
On many remote sites the cost of diesel is not the fuel price, it is the delivery: a truck, a road, a season when the road is impassable, and someone whose job it is to manage it. Reducing generator runtime can also reduce fuel deliveries. Quantify the potential change using site load data, generator records and the actual delivery arrangements.
That is why the business case should be built from the site’s actual generator log rather than from a modelled average. If you have the running hours and the fuel deliveries, the comparison is straightforward and it is specific to your site rather than to a rule of thumb.
Specifications at a glance
Configuration reference
Swipe horizontally to view all columns →
| Item | Typical specification | What decides it |
|---|---|---|
| Site load | From 10 kW to several megawatts | Connected load, diversity and the shift pattern |
| Battery chemistry | Lithium iron phosphate (LFP) | Cycle life, ambient temperature and safety requirement |
| Storage capacity | Commonly 100 kWh to several MWh | Autonomy hours and the generator strategy |
| Inverter / PCS | Bi-directional, 100 kW upwards, paralleled | Peak load, surge headroom and redundancy philosophy |
| Generator | Retained or adjusted after reviewing worst-case duty and reserve | Peak load, motor starting, charging demand and the refuelling interval |
| Control | Hybrid controller managing state of charge and generator start | Fuel strategy and the autonomy target |
| Surge headroom | Sized to motor starting current, not running current | Largest motor and whether it starts loaded |
| Enclosure | IP54 to IP65, filtered ventilation or air conditioning | Ambient temperature, dust and salt exposure |
| Ambient design | Operating temperature and derating curves confirmed for each selected unit | Site climate, enclosure cooling and the selected equipment datasheets |
| Compliance documentation | Applicable product listings, safety test reports and transport documentation confirmed for the selected configuration | Destination market, installation scope and local authority requirements |
| Documentation | Load study, single-line diagram, autonomy calculation and commissioning requirements as applicable | Document scope and responsible parties confirmed in the proposal |
| Warranty | Battery 10 years; inverter 10 years; modules up to 30 years performance | Model and order terms |
Figures are selection references. Confirm the final ratings, dimensions, available certifications and warranty against the current datasheet and written proposal for the selected model or system.
Questions buyers ask about off-grid industrial power
Can we remove the generator completely?
Sometimes, on a duty where the load is predictable and the climate is kind. It moves all the risk onto the array and storage, so it needs either a large autonomy or an accepted outage risk. Compare a retained-generator configuration with full solar-and-storage autonomy using the site’s reliability target, worst-weather conditions and lifetime costs.
How many generator hours does it typically remove?
It depends on the load profile and the climate, and it should be calculated rather than estimated. Bring the generator running hours and we will model it against the site’s solar resource.
What happens if the battery reaches empty?
The controller starts the generator before that point, at a state of charge set during commissioning. The setpoint is a chosen trade-off between fuel and battery life, and it is worth deciding deliberately rather than leaving it at a default.
How long does the battery last in a hot climate?
LFP cycle life is quoted at a reference temperature, and high ambient temperature shortens it. Keeping the enclosure within its designed range is what protects the warranty, which is why ventilation or cooling is a specification item rather than an accessory.
Can the system grow with the site?
Yes, if the inverter and the enclosure are sized for it at the start. Adding storage later is straightforward; adding inverter capacity to a container that was sized tightly is not. Saying now that the site will grow is the cheapest way to allow for it.
What to send us
Send the load list or the generator log, the shift pattern, the site location and climate, and whether the generator stays. We come back with a load study, the storage and inverter configuration, the modelled generator hours remaining, and a written delivery date.
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Send the load profile and the worst-case outage
With the load profile, the longest outage you must ride through, and the site conditions including temperature and dust, we size against the worst case rather than the average.
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