Solar + battery vs diesel: cutting generator costs
Hospitals, cold stores, petrol pumps and rice mills often run diesel generators through power cuts. Solar can cut the grid bill in the day, and a battery can carry critical loads through shorter outages, so the generator runs less.
What does a unit from your generator cost?
Diesel cost per unit = price per litre ÷ units your DG set produces per litre. Enter your own figures.
An estimate from your inputs
- Diesel cost per unit
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- Diesel spend
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- Diesel used
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Why the cost per unit matters
Every unit a battery or solar supplies during an outage is a unit your generator doesn't have to make. Knowing what a diesel unit costs you shows how much of a battery's cost could be offset by running the generator less.
How solar, battery and generator work together
- Solar supplies your site in the day and reduces the units you buy from the grid. On its own, an on-grid plant switches off during a power cut for safety.
- A hybrid inverter with a battery keeps chosen critical loads running through an outage, and lets solar keep charging and supplying them.
- The generator stays as the backup for long outages and for loads too large for the battery.
The size of the battery depends on which loads must stay on, and for how long. Sizing it for everything is usually far costlier than sizing it for critical loads only.
Where it matters most
Hospitals and clinics
Operation theatres, ICUs, refrigeration for medicines and IT systems cannot wait for a generator to start. Solar for hospitals and healthcare · hospital sector guide with a worked example
Cold storage
Refrigeration runs every day, and temperature has to hold through power cuts. Solar for cold storage · cold storage sector guide with a worked example
Petrol pumps
Dispensers, lighting and billing need power through outages. Petrol pump sector guide with a worked example
Rice mills
Heavy daytime motor loads suit solar; the battery question is about which processes must not stop. Rice mill sector guide with a worked example
Questions to ask before you buy a battery
- Which loads must stay on in an outage, and how many kW do they draw?
- How long are your typical outages, and how often do they happen?
- What battery chemistry is offered, what is its warranty, and how many cycles does the warranty cover?
- How does the system hand over to the generator when the battery runs low?
More on batteries: is solar battery storage worth it? and on-grid vs off-grid vs hybrid solar. When you're ready, book a free power audit and we'll look at your loads with you.