What size generator for a church, a school or a meeting hall?

A church, a school or a meeting hall is sized like any other building. Add up the running power of the lights, fans, sound system, projector and computers, then add a 25% reserve. Then check that the generator can take the start-up surge of the largest motor while everything else is running, and keep the larger of the two values. Using our generator finder, the sample church hall needs 12.4 kVA and the six-classroom school 19.0 kVA.

The loads in both examples are assumptions, not measurements: replace them with your own equipment. For a shop, a clinic or a workshop, see our three worked examples.

Which appliances should you count in a church, school or hall?

Count everything that runs at the same time during a service, a lesson or a meeting:

• lighting: number of lamps × the power of each lamp;
• fans and air conditioners;
• the sound system: mixing desk, amplifiers, powered speakers, wireless microphones;
• instruments: keyboard, guitar and bass amplifiers;
• the projector, computers and printer;
• the water pump, if it is wired to the generator circuit.

For the sound system, read the power consumption (input power) on the rating plate or in the manual of each unit. Do not use the output power advertised for the speakers: it is not what the unit draws from the mains.

Air conditioners and pumps are motors. When started direct-on-line, a motor briefly draws far more current than it does while running. Our finder counts that surge as three times its running apparent power. That motor, not the sound system, often sets the generator size.

The finder has no “sound system” or “projector” row. In that case, choose “I have the total load (kW)”: enter the sum of your appliances, then the power of the largest motor and how it starts. This method assumes everything runs at once. That is the case during a service or a lesson. With “List my appliances”, the finder applies a simultaneous-use factor for your application (0.6 for a school), so the result will be lower than in our examples.

Example 1: what size generator for a church hall with a sound system?

A church hall of about 300 seats, with no air conditioning, needs 12.4 kVA. Here are the assumptions we used:

Finder settings for these examples: “Compact generator” (air-cooled) at the first step, “Continuous” use (prime power) and “Any” phase, unless stated otherwise.

With these settings, the finder suggests the Brux BX16000DSE3-3D: a 15 kVA (12 kW) silent diesel, three-phase 220/380 V. The model just below, the BX15000DSE3-3D, is not enough at its 11.9 kVA prime rating. With “Heavy-duty generator” (water-cooled), it suggests the 13 kVA generator with a Perkins 403A-15G1 engine.

And without the pump? If the pump stays on the SNEL grid, or you fill the tank before the service, the load drops to 5.75 kW. The fans are small motors: their start-up changes nothing. The required power falls to 9.0 kVA. Air-cooled, the finder then suggests the Brux BX11000DSE3-3D, a 9.4 kVA silent three-phase set. Water-cooled, it still suggests the 13 kVA set, the smallest in that range.

Note: on a three-phase set, each phase delivers only about one third of the rating, so 5 kVA on the BX16000DSE3-3D and 3.1 kVA on the BX11000DSE3-3D. The loads in a church hall are single-phase, so have an electrician spread them over the three phases, with the sound system, the pump and the lighting on different phases. A 2.5 kW (3.1 kVA) sound system takes up a whole phase of the BX11000DSE3-3D on its own. In that case, choose the single-phase BX11000DE or a larger three-phase set. Our single-phase or three-phase guide explains how the load is shared.

On single-phase, none of our generators covers 12.4 kVA: our largest single-phase set is 9.4 kVA, and all our water-cooled sets are three-phase. Two options: move to three-phase, with the phases balanced by an electrician, or take the pump off the generator circuit. Without the pump, the 9.0 kVA need on a single-phase 220 V supply leads to the Brux BX11000DE, a 9.4 kVA open-frame set. Our largest single-phase silent diesel, the Bison BS11000DSE, is rated 8 kVA: too small here.

Example 2: what size generator for a six-classroom school with a computer room?

A six-classroom school, with an air-conditioned computer room and a head teacher's office, needs 19.0 kVA. Here are the assumptions we used:

This need is above our air-cooled range, which stops at 15 kVA. The finder therefore suggests a 20 kVA generator with a Perkins 404A-22G1 engine: 20 kVA prime power, three-phase, water-cooled. This three-phase set delivers about 6.7 kVA per phase: put the air conditioner on a lightly loaded phase, because its 5.63 kVA surge nearly fills a phase. If you plan to add equipment, run the calculation again with a growth margin: the next step up is the 30 kVA generator with a Perkins 1103A-33G engine.

To repeat these calculations with your own appliances, open our generator finder.

Weekly or daily use: which type of generator should you choose?

How often the generator runs matters as much as its size.

• A few hours a week (services, meetings, parties): an air-cooled diesel is suitable. These sets are designed for intermittent use.
• Several hours every day (a school, a hall rented out on weekdays): choose a water-cooled diesel. Our water-cooled range starts at 13 kVA.
• A small chapel or meeting room: our petrol generators go up to 7 kW, and our inverter generators up to 5 kW. These sets are rated in kW on our datasheets; the finder compares your kVA need directly with that figure, which leaves a margin.

Our guides diesel, petrol or inverter and air-cooled or water-cooled explain these choices.

How do you keep generator noise down during services and lessons?

A generator placed too close drowns out the preacher or the teacher. Three simple rules:

• choose a soundproof set when it stands near the hall;
• place it away from windows and doors, with the exhaust pointing away from the building;
• keep open-frame sets for a ventilated room or shelter, away from people.

The datasheets of our Perkins-engine generators from 13 to 100 kVA state 75 dBA at 3 m for the soundproof version. For a Brux model, ask us for its sound level. Our soundproof or open-frame guide compares size, weight and noise. For location, ventilation and connection, see our guide to installing a generator safely.

Frequently asked questions

What size generator for a sound system alone?

Add up the consumption printed on each piece of sound equipment, then apply the same method: divide by 0.8, then add 25%. With the 2.5 kW sound system from Example 1, that gives 3.9 kVA with nothing else connected. Then add the lighting and the fans.

Should you buy or rent a generator for an event hall?

For a one-off event, renting avoids buying a generator that will only run a few days a year. For events every week, buying makes more sense. See our generator rental page. Our renting or buying guide lists what to prepare.

Can one generator serve both a church and the school next door?

Yes, if the two uses do not run at the same time. Lessons take place on weekdays and services mostly at weekends: size the generator on the more demanding use, including the equipment shared by both (pump, outdoor lights). Run one calculation per use and keep the larger result. If activities overlap, for example a meeting during lessons, add their appliances together and enter that total in the finder to get the size.

Ask for a quote

On WhatsApp at +243 903 005 060, send us your list of appliances, the number of seats and the usual length of your power cuts. Our team will suggest a suitable set from our generators. Prices on request. You can also visit our showroom in Gombe, Kinshasa (No. 26 Av. des Huileries, opposite the INRB), Monday to Friday 8 am to 5 pm and Saturday 11 am to 4 pm.

Examples calculated with the finder's method; the final sizing is confirmed by our technical team. Sources: manufacturers' datasheets (Perkins engines, Bison and Brux generators) and the calculation method of the MK Energies & Services generator finder.