Generators are one of those investments people only think hard about once something goes wrong. A unit that’s been running fine for years suddenly starts surging, refuses to start, or begins leaking oil, and the next question is always the same: how much is this going to cost to fix? Whether it’s a small petrol backup unit for a home or a diesel standby generator running a whole office block, repair and parts pricing varies a lot depending on the brand, the size of the unit, and whether the part is genuine, OEM-compatible, or a cheaper aftermarket alternative.
Below is a breakdown of typical service costs and spare parts pricing, based on what technicians and suppliers commonly charge for residential and commercial generator work.
What Drives the Cost
A few things consistently push prices up or down. Engine brand matters a lot — Perkins, Cummins, and Volvo Penta engines carry pricier parts than generic Chinese-built units, simply because the components are imported and often need to be sourced specifically. Generator size is another factor: a small 5–10 kVA petrol unit is cheap to service compared to a 100 kVA+ diesel standby generator, where even routine maintenance involves more oil, larger filters, and more labour hours. And then there’s the question of genuine versus aftermarket parts — genuine alternator windings or control modules can cost two to three times more than compatible substitutes, though they typically last longer and come with better warranty support.
Fuel type also shapes the kind of work involved. Diesel generators need more attention to injectors, fuel pumps, and glow plugs, while petrol units tend to have more carburettor and spark plug issues. Age plays a role too — a generator that’s ten-plus years old may need parts that are no longer stocked locally, which means longer wait times and higher import costs.
Estimated Cost of Services
| Service | Estimated Cost Range (KES) |
|---|---|
| Basic diagnosis / fault assessment | 1,500 – 3,000 |
| Standard servicing (oil, filter, general check) | 3,000 – 8,000 |
| Engine overhaul (partial) | 25,000 – 60,000 |
| Engine overhaul (full/major) | 80,000 – 250,000 |
| Alternator repair / rewinding | 8,000 – 30,000 |
| Automatic Transfer Switch (ATS) repair | 5,000 – 20,000 |
| Control panel / AVR troubleshooting | 3,500 – 12,000 |
| Fuel system cleaning / injector service | 4,000 – 15,000 |
| Cooling system repair (radiator, water pump) | 5,000 – 18,000 |
| Installation and commissioning | 10,000 – 40,000 |
| Load bank testing | 8,000 – 25,000 |
| Emergency call-out / after-hours service | 2,000 – 6,000 |
Costs are indicative and exclude spare parts unless otherwise noted. Larger commercial units at the higher end of the kVA range typically fall toward the top of these ranges, and a written quote should always be requested before work begins.
Common Spare Parts and Their Price Ranges
| Spare Part | Estimated Cost Range (KES) |
|---|---|
| Air filter | 800 – 3,500 |
| Oil filter | 700 – 2,500 |
| Fuel filter | 900 – 3,000 |
| Spark plugs (petrol units) | 300 – 1,200 |
| Glow plugs (diesel units) | 600 – 2,000 |
| Battery (standard lead-acid) | 6,000 – 18,000 |
| Alternator (complete unit, small/mid range) | 25,000 – 90,000 |
| AVR (Automatic Voltage Regulator) | 4,000 – 15,000 |
| Control module / genset controller | 15,000 – 60,000 |
| Radiator | 15,000 – 45,000 |
| Water pump | 5,000 – 15,000 |
| Fuel injector (per unit) | 3,500 – 12,000 |
| Fuel pump | 6,000 – 20,000 |
| Starter motor | 8,000 – 25,000 |
| ATS (Automatic Transfer Switch) unit | 20,000 – 80,000 |
| Belts (fan/alternator) | 800 – 3,000 |
| Muffler / exhaust silencer | 4,000 – 15,000 |
| Engine gasket set | 2,500 – 9,000 |
Prices for major components like alternators, control modules, and ATS units swing widely because they’re sized to match the generator’s capacity — a part rated for a 10 kVA unit costs nowhere near what the same component costs for a 200 kVA commercial genset.
Repair or Replace
For anything below roughly 40–50% of the cost of a new equivalent part, repair usually makes more financial sense, especially for components like alternators or control panels that can often be rewound or reprogrammed rather than replaced outright. Once a generator starts needing frequent engine work — multiple overhauls within a short span, recurring fuel system issues, or a control module that keeps failing — it’s worth getting a technician to assess whether continuing to repair is actually cheaper than replacing the unit altogether, particularly for older diesel generators where sourcing OEM parts is becoming harder each year.
Routine servicing remains the cheapest way to avoid the bigger bills. Generators that sit unused for long stretches between power outages are actually more prone to starting issues, battery failure, and fuel degradation than ones that run regularly, so a basic quarterly check tends to pay for itself by catching small problems before they turn into engine-level repairs.
Would you like me to follow this up with any of the below?
- A breakdown comparing repair costs by generator brand (Perkins, Cummins, Mikano, Lister)
- A maintenance schedule guide for standby vs. backup generators
- A companion article on solar/inverter backup system costs for comparison
- A short buyer’s guide on choosing between diesel and petrol generators