Diesel light plants have been the default on jobsites, mines, and bases for decades. They're familiar, they run as long as there's fuel, and every rental yard has them. Solar light plants are a different tool: they trade the engine and fuel tank for solar panels and a lithium battery. Neither is right for every job. Below we compare them on fuel, maintenance, noise, emissions, runtime, and cost, using Solight's published specs where we can and plain industry facts where we can't.
How each one works
A diesel light plant uses a small engine to drive a generator, which powers the lights. It produces light whenever the engine runs, and someone has to start it, stop it, and refuel it unless it has automatic controls.
A solar light plant (or solar light tower) charges a battery bank from a solar array during the day and runs LED floods from that battery at night. Solight towers run dusk-to-dawn automatically, on a digital timer, or with manual switches. For example, the SLT-1200 pairs a 1,200 Watt three-panel array with a lithium battery bank and four 100 W LED floods on a 30 ft mast.
Fuel
This is the biggest difference. A diesel light plant burns fuel every hour it runs, and somebody has to haul and pump that fuel. A solar tower uses no fuel for lighting.
Solight's homepage gives an annual estimate for one tower running 10 hours a day, 5 days a week, 52 weeks a year, with diesel at $5.79/gallon and refueling every 5 days:
| Annual cost (Solight estimate) | Diesel | Solar |
|---|---|---|
| Fuel and refueling labor | $9,785 | $0 |
| Servicing | $6,586 | $400 |
| Total | $16,371 | $400 |
Your numbers will differ with fuel price, hours, unit size, and how far fuel has to travel. On remote mines and bases, the fuel run itself (truck, driver, time) adds to that.
Maintenance
Diesel engines need regular service: oil and filter changes, fuel system care, and the occasional repair. They also have to be started and checked. Solight's solar vs. diesel page notes that diesel towers "must be started manually daily, maintained monthly, and… refueled constantly."
Solar towers have no engine. Solight describes its towers as low maintenance: the lithium batteries need no routine service, and panels mostly need to stay clean. Rain often handles that, and in dusty areas a periodic wipe-down helps. You'll still want to inspect cables, the mast, and the trailer, as with any towed equipment.
Noise
A diesel engine runs the whole time the lights are on. Next to a neighborhood, an event, a guard post, or a crew working by hand, that noise matters. Some projects have night-noise limits. A solar tower has no engine, so it runs silently. That's one reason Solight's SLT-450 (450 Watt array, 32,000 lumens, 16 ft telescoping mast) is popular for events and parking lots.
Emissions and smell
Diesel engines produce exhaust at the light plant, which is where people are working. Solar towers produce no emissions at the site and have no fuel smell. They also don't need fuel storage, so there's no on-site spill risk from the tower.
Runtime and weather
Here diesel has a real advantage. A diesel plant runs as long as it has fuel, regardless of weather. A solar tower runs as long as its battery has charge, and that depends on battery size, light load, season, and sun.
What Solight publishes:
- The SLT-450 is a compact event light rated for about 5 hours of light daily.
- The SLT-1200M military tower: on a full charge, its usable battery (90% of 10.24 kWh, about 9.2 kWh) runs its 400 W lights for about 23 hours, which is up to two full nights of about 11–12 hours each, even without sun in between.
If you need more margin, there are three ways to get it: a bigger battery and array, such as the SLT-2500 with 20.5 kWh; extra charging sources, such as the SLT-1200M's optional AC plug, NATO slave, or wind turbine; or a hybrid. The SLT-4100H pairs a 4,100 Watt solar array and 20.5 kWh battery with a Kubota generator and 100-gallon tank as backup, so it runs on solar first and only uses fuel when it has to.
Light output
Modern solar towers use LED floods, and Solight publishes the output for each model. The SLT-450 makes 32,000 lumens, the SLT-1200M military tower is rated at 64,000 lumens, and the SLT-2500 and SLT-4100H make up to 128,000 lumens. Compare these against the area you need to light rather than against a diesel unit's wattage. The full table is on our solar lighting page.
Upfront cost vs. operating cost
Solar light towers usually cost more to buy than comparable diesel units. Solight's solar vs. diesel page notes that a solar light tower pays for itself in the first 1–3 years of use. How fast that happens depends on how many hours you run and what fuel and service cost you. If you're not ready to buy, renting lets you test solar on a real job. See solar light tower rental.
When diesel or hybrid still makes sense
- Very high continuous power loads beyond lighting, such as tools or site trailers
- Long stretches of heavy cloud with no other way to charge
- Short jobs where a diesel unit is already on site and fueled
For many of these cases, a hybrid like the SLT-4100H or a solar tower with backup charging covers the gap.
Where this matters most
- Mines and remote yards: fuel runs are long and sites go unwatched. See mining site security.
- Military bases and training areas: fuel resupply, noise, and unattended operation. See solar lighting for military bases.
- Security: a solar tower keeps cameras recording when a diesel plant would be shut off. See solar security towers.
Frequently asked questions
Is a solar light plant cheaper to run than a diesel light plant?
Usually, yes. A solar light plant uses no fuel for lighting and needs little routine service. Solight's homepage estimate for one tower running 10 hours a day, 5 days a week, is about $16,371 a year for diesel versus $400 for solar. Your costs will vary.
Can a solar light tower run all night?
Yes. Solight towers run dusk-to-dawn from their lithium battery bank. How many nights a tower can run without sun depends on battery size and light load. Larger models and hybrid units add margin.
Are solar light towers quieter than diesel?
Yes. Solar light towers have no engine, so they run silently. Diesel light plants run an engine the entire time the lights are on.
What happens to a solar light tower on cloudy days?
The battery bank carries the load. For long cloudy periods, choose a larger battery and array, add a charging option such as AC or wind where available, or use a hybrid tower like the SLT-4100H with a backup generator.
Can I rent a solar light plant before buying?
Yes. Solight rents solar light towers from Mesa, Arizona, across Arizona, California, Utah, and Nevada, and purchases ship nationwide. Rental rates are listed on our solar lighting page.
Talk to Solight
Not sure whether solar, diesel, or a hybrid fits your site? Tell us the hours, area, and location. Contact Solight or call 480-626-2044, Monday–Friday, 8am–5pm Arizona time.