Generator Running Cost Calculator

What actually drives running cost

Purchase price is only part of the picture. What decides whether a generator makes sense for daily use is the cost per kWh, and that is dominated by fuel. A diesel set typically lands between 0.25 and 0.45 per kWh at realistic load, depending on fuel price and how well the set is matched to its load.

Maintenance — oil, filters, and periodic servicing — adds a smaller but real amount on top. The calculator lets you put in your own figure rather than assuming one.

Where the money goes

• Load matching. Running a set well below its rating raises cost per kWh sharply. This is the single biggest lever.
• Fuel price. Obvious, but it varies enormously by market, so use your own local figure.
• Maintenance interval. Short, regular servicing is cheaper over the life of the set than infrequent major repairs.
• Hours per day. Total cost scales linearly with hours; cost per kWh does not improve with longer runs.

Common questions

How do I compare this against my grid tariff?

Use the cost per kWh figure. If it comes out below your tariff, running the generator for continuous duty is cheaper; if it is above, reserve the set for backup and peak shaving.

Does the result include the purchase price?

No. It covers fuel and the maintenance allowance you entered. Depreciation and major overhauls are excluded, because they depend on how many years you keep the set.

Why is cost per kWh worse at low load?

Because fuel consumption does not fall in proportion to load. At 25% load a set may still burn half its full-load fuel, so the same litre produces far fewer kWh.