Fuel and Cooling

What size do you need?

Buy a High-Quality Brand (Procurement Specifications)

Pay Attention to the Noise Factor

Have it Installed By a Professional

Be Careful Where You Locate It and How You House It

Operation & Maintenance

Generator Fuel and Cooling

Fuel – Generators may use gas or diesel – it is important to ensure adequate fuel is available. Diesel generators will be in general more durable and reliable. Ideally you want to use a fuel that you can safely store. In an emergency context you don’t have time to dash out and fill some jugs. You need to have a reserve sufficient to get you by for at least 72 hours.


    • Diesel is the best fuel there is for backup power. A typical diesel generator delivers nearly twice the power per gallon, when compared to petrol. Diesel is a more powerful fuel, and diesel engines are high compression, so they burn fuel at higher temperatures releasing greater energy.
    • Diesel stores for long periods and is a lot safer to handle and store than petrol.
    • In some countries you can buy diesel without paying road taxes, which can be a big cost savings.
    • In extreme cold climates an anti-gel additive might be needed so that the fuel remains fluid. Depending on how you store your fuel and the climate where you live this can be a critical issue. In most cases this is not a problem, but it is a factor to be aware of.
    • Diesel engines last much longer than any other engine type. They have dramatically fewer things to go wrong and run much better than petrol in foul weather. They have no carburetor, no points or electrical system. All they need is fuel, air, and compression. The bigger water cooled units can run 20,000 to 40,000 hours before an overhaul, easily 10-20 times longer than a petrol generator.
    • One of the explanations for longer life is the fact that diesel engines used for power generation usually run at slower RPM speeds, and as a general rule, the slower you go the longer you last. Petrol generators (and a few small diesels) run at 3600RPM, explaining their shorter lifetimes.
    • Diesel generators are amazingly efficient. Load and fuel consumption track very closely, due to the nature of fuel injection and the fuel.


    • Petrol has the advantage of being readily available, and in an emergency petrol can be siphoned from a vehicle and used in the generator. (If necessary, make sure you buy a siphon kit!)
    • Be sure your petrol generator is designed for cold and wet weather operation. Some work great year around, but many cheaper generator imports from China do not run reliably in the winter or in wet weather conditions. The highest probability is that you’ll need your generator and the weather will be bad. Honda have dramatically improved bad weather operation, fuel consumption, reduced oil consumption, and are much easier to start than they used to be. The newer engines are excellent.
    • A good 5KW+ petrol generator can be purchased for less than $1,500 and is nice to have around.
    • NOTE: Petrol generators often waste fuel when lightly loaded. This means that, for greatest efficiency you should keep a significant load on the generator, or turn it off.


Water-Cooled – Water-cooled diesel generators are (with a few possible exceptions) much more reliable. Since there is more control over expansion and contraction of metal parts and such generators usually have full-pressure lubrication, wear is under better control. Water-cooled diesel generators are designed for more serious applications and are generally built to tighter specifications. Tighter tolerances can be more easily maintained because of a more constant operating temperature.

Air-Cooled – If you are not going to need to run your generator that often, or you just want one for emergencies, air-cooled generators are a good choice since they are cheaper to buy.

Back to Top


What Size Generator Do You Need?

In general, temporary offices or mobile teams will rely on smaller generators, from 2.5 to 5 kw. Permanent or semi-permanent offices with large staff and electricity needs will require from 8 to 30+ kW.  We’ve attached a table with a list of common generator sizes and some idea of what each will power and for how long.

Common Generator Sizes & Capacities

But that document will just give you a general idea.  In order to purchase a generator that will supply most of your power in a guest house or office, you must go through a sizing exercise.

In brief, you determine necessary generator size by:

    1. Listing all the appliances you will need to run with the generator,
    2. Finding out how much power each uses,
    3. Adding up those amounts, and finally
    4. Increasing the total amount by 30%

Here are some tools that should help you get an idea of what you will need:

List of common appliances and approximate wattage

Generator Sizing Worksheet, Guest House

Generator Sizing Worksheet, Office

In reality, there is more to it than the simple calculations on the sheets linked above – especially for large generators that you will rely on for all your power.  So, if you are going to spend a lot of money to buy a generator to power an entire office or residence, call professionals – they can and should do a generator sizing exercise as part of their bidding process.

Some general things to know:

    1. Air conditioner units, electric heating units, and water heaters use the most power. If you will run any of these, the generator size you need will increase significantly.
    2. Electronic exercise equipment (e.g. a treadmill) can also require a lot of power.  If the compound will eventually hold this kind of machinery, make sure to figure it in now.
    3. When calculating the size of the generator allow for startup surge for AC, heater units, and items with motors. The startup surge can be 3 to 4 times the running wattage.
    4. Generators run most efficiently at approximately 70% capacity. Pick a generator that is 25% to 30% above your projected power needs.
    5. If you are planning to use the generator to charge an inverter, you should also figure this in to the generator’s capacity.

If you are in a remote area (where it will be hard to get maintenance and parts) and will be completely dependent on generator power, consider buying two generators and alternating their use.

Back to Top


Buy a High-Quality Brand (Procurement Specifications)

If you are buying a large generator on which you will depend for a majority of your power needs, spend the money necessary to get a high-quality, reliable machine.  That being said, don’t be snookered by brand name or high prices. Brand names are often hijacked by off-shore companies trying to make money on an old reputation that is no longer valid. Take a little time and look around, with the understanding that spending the money up front will actually save you money (and hassle) in the long term.  Choose a well-known brand name such as Caterpillar, Wilson, Honda, Briggs and Stratton, Troy-Bilt, Yamaha, or Perkins.   Also, there are a lot of Detroit Diesel 20kW generators that are built to last.  You can find others on the internet if you have a good connection.  Buy from authorized dealers.

Tip: When you look at the specifications of a generator make sure that the engine has a horsepower rating of 2HP for every 1KW of output. For example, a 5,000W generator should have at least a 10HP rating. Once you know this it’s pretty easy to spot exaggerated ratings. Reputable companies will meet this standard, but there are many smaller companies looking for an edge in marketing that provide optimistic (to say it nicely) ratings.

Important: Consider all additional items you will need when ordering a generator – wiring/extension cords, multi-plug strips, light bulbs and hardware for installation.

Generators need to be tested prior to deployment and field teams need to be trained on use, maintenance and trouble-shooting.

Procurement location:  Local procurement is recommended. Ensure purchasing from a reputable dealer and quality brand. Ensure brand has available spare parts for maintenance in local market.

Shipping and cost details:

Size COT* Packaging Weight Dimensions Estimated Cost
4kw 15.5hrs 1 unit with metal frame 74.4 kg 68.1 x 57.9 x 57.2 cm $1,499 USD
5kw 11.0hrs 1 unit with metal frame 80.1 kg 68.1 x  57.9 x  57.4 cm $1,649 USD
6.5kw 10.0hrs 1 unit with metal frame 82.6 kg 68.1 x 57.9 x 57.7 cm $1,849 USD
7kw 12.0hrs 1 unit with metal frame w/ wheels 119 kg 119.8 X 70.1 X 72.1 cm $3,800 USD
10kw 7.2hrs 1 unit with metal frame w/ wheels 182.8 kg 142 x 67.8 x 89.2 cm $5,000 USD

* Continuous Operating Time (COT) on full tank of gas and @ 1/2 load



  • Noise reduction hood
  • Extra air filters, fuel filters, oil filters
  • Spare parts

Back to Top


Pay Attention to the Noise Factor

There are 3 types of large (> 8 kva)  generators

    1. Non-silent
    2. Semi-silent
    3. Silent

The difference is in the quality of insulation in the casing and on the exhaust.  The engine of silent and semi silent generators are housed in sound-proof casing while non-silent generators have no casing.   Silent generators are more expensive.   A silent generator creates 60 to 70 decibels (DB(A)) at 7 meters from the generators – slightly less than the sound of a diesel car engine idling.   Non-silent generators are very loud, disturbingly loud.

Back to Top


Have it Installed By a Professional

Have a qualified experienced electrician install the generator.  In fact, if you will be powering a house and or office with a generator, call the professionals in to help you size the generator as well.

Back to Top


Be Careful Where You Locate It and How You House It

  1. Generators produce noise. Locate the generator where it will provide the least disturbance to the office, residence and your neighbors.
  2. The generator should be protected from the elements, covered by a roof.
  3. Generators produce exhaust gases and heat. Make sure the generator is well ventilated.  If the generator is to be housed in a room (as opposed to a roofed outdoor mesh enclosure), ensure adequate openings are provided for air intake to cool the engine and exhaust outlets to remove fumes and hot air.  The generators’ radiator and exhausts systems should be located close as possible to the ventilation opening in the wall so as to prevent the buildup of heat and fumes in the room. A poorly ventilated room will cause the generator to overheat and function less efficiently.
  4. Generators produce carbon monoxide. Do not locate them or their exhaust system outlets next to or under windows or other building ventilation systems.
  5. Put the generator on a level solid surface. Consider a concrete base for large generators.
  6. Set up the generator so you can access the refueling and other maintenance areas easily.

Back to Top


Operation & Maintenance of your generator

  1. Follow good safety guidelines, and make sure that your generator is installed properly and well ventilated. It’s better to get the advice of an electrician or mechanic that you know. Make sure that you do things right and get a second opinion when you can. Always pick the safest option. Once you have your system in operation it will be there for years to come so don’t get impatient.
  2. Even a cheap generator can last a long time if properly maintained. CHANGE THE OIL, use synthetic oil, and keep the generator clean. When a generator is used often you get more time out of the generator, so make sure it is run every week for 15-30 minutes. Some generator systems do that automatically. Look for the feature.

Back to Top