Find the right generator

1. 1

   List your appliances. Multiply each appliance's power (in watts) by how many you have, then add them up. That is the total connected load, in kW. If you already know the total load, enter it directly (method B).

2. 2

   Allow for simultaneous use. Not everything runs at once. With method A, the finder applies a factor for your application, from 0.6 (hotel, school) to 0.9 (telecom site). You can also pick high use (×0.9) or low use (×0.6). With method B, the load you enter is used as is.

3. 3

   Convert to kVA. A generator is chosen in kVA, which is apparent power. With a power factor of 0.8: kVA = kW ÷ 0.8.

4. 4

   Add a 25% reserve. This way the generator does not run at full load all the time.

5. 5

   Check the largest motor's start-up. When it starts, a motor (air conditioner, pump, compressor, elevator) draws several times its running power. The finder counts ×3 direct-on-line, ×2 star-delta, ×1.5 with a soft starter and ×1.2 with a variable-speed drive. It adds this surge to the load of everything else, then a 10% margin. It keeps the larger of the two values: the 25% reserve or the start-up requirement.

6. 6

   Correct for the site. Above 1,000 m altitude, a generator loses about 3.5% of its power per 300 m, up to 25%. Above 40 °C, it loses about 2% per 5 °C, up to 20%. In Kinshasa (about 300 m and 32 °C), no correction is needed.

7. 7

   Plan ahead. Add 10, 20 or 30% if more equipment is planned.

8. 8

   Pick the generator. The finder keeps the smallest generator whose rating covers the need. It compares the need with prime power for continuous use, or with standby power if the generator only runs during outages. It also shows the next smaller and the next larger model for comparison.

Water-cooled set, 10 lights of 100 W, 4 air conditioners of 1,500 W, 2 refrigerators of 300 W and a 1,100 W water pump, with low simultaneous use:

Result: 11.3 kVA. The finder recommends the 13 kVA water-cooled diesel generator (403A-15G1, 13 kVA · 10.4 kW), or the 15 kVA · 12 kW model for extra headroom.

Default values in the tool. Check your appliances' rating plates: every value can be changed in the finder.

kW is the useful power your appliances consume. kVA is the apparent power the generator must supply. With a power factor of 0.8: kW = kVA × 0.8.

Prime power is what the generator can deliver for unlimited hours per year under a varying load. Standby power is higher, but it is meant for outages only. Our datasheets give both: for example 100 kVA · 80 kW prime and 110 kVA · 88 kW standby for the set with the Perkins 1104C-44TAG2 engine. Pick “Standby” in the finder if the generator only runs during outages. When unsure, the calculation uses prime power. Our guide to prime and standby ratings sets out the ISO 8528-1 definitions.

MK Energies offers 18 air-cooled generators (Bison and Brux: gasoline, inverter or small diesel) from 2 kW (gasoline) to 15 kVA (diesel), single- or three-phase. We also offer 25 water-cooled Perkins-engine diesel generators from 13 to 2,000 kVA, three-phase. Gasoline and inverter sets are rated in kW. If your need falls outside the range you chose, the finder points you to the other one.