Most RMG factories in Bangladesh already own diesel generators. They were bought to protect production from load-shedding, and they do that job. The question is what that protection costs per unit of electricity, and whether a hybrid solar system with battery storage can do the same job for less.
The model
We modelled a factory with a 1 MW average daytime load, single-shift operation six days a week, and a year that includes a realistic pattern of summer load-shedding. We compared two setups: grid supply with diesel backup, and grid supply with a 1 MWp hybrid solar plant, a battery sized to ride through typical outages on critical lines, and the existing gensets kept as a last resort.
Diesel costs in the model include fuel, lubricants, routine servicing and overhauls spread across running hours. They do not include the capital cost of gensets the factory already owns, which keeps the comparison conservative. The hybrid case includes the full capital cost of modules, inverters, battery and installation, recovered over the life of the system, together with monitoring and preventive maintenance.
| Metric | Grid + diesel | Grid + hybrid solar |
|---|---|---|
| Cost per backup unit | Tk 28–32 | Stored solar, no fuel |
| Daytime grid purchases | 100% | ≈ 55–65% |
| Genset running hours | Baseline | ≈ 70–80% lower |
| Switchover to backup | 8–12 seconds | < 20 ms on critical lines |
| Fuel price exposure | Full | Minimal |
Where the savings come from
The hybrid system saves money in two distinct ways. During normal operation, solar generation displaces grid purchases at the blended commercial tariff. During outages, stored energy displaces diesel, which is by far the most expensive electricity the factory buys. Because diesel costs more than twice the grid tariff per unit, every outage hour served by the battery is worth considerably more than a normal hour of solar.
“The genset is still there. It just stops being the first thing that starts when the grid goes down.”
Downtime is the hidden line item
A cost-per-unit comparison understates the case for dyeing, printing and finishing lines, where an 8–12 second genset start gap can spoil a batch. A battery system with sub-20 millisecond transfer means those loads never see the outage at all. For many plants, avoided spoilage and rework is worth as much as the energy savings.
When diesel still wins
- Sites with very little usable roof relative to load.
- Plants facing long multi-day outages, where battery sizing becomes uneconomic.
- Short remaining lease terms that do not allow a 4–6 year payback.
For most grid-connected RMG plants with sound roofs, though, a hybrid system lowers the cost per unit and improves uptime at the same time. The only way to be sure for your site is to model it with your own load and outage data.
Written by
Engineering Desk
Design & EPC team, Emerged Power
Our design engineers write about the details that decide whether a plant hits its yield — from purlin spacing to string sizing.