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How big is a tree, I mean, a Generator?

Sizing and selecting a generator for your home, office or mission critical environment can be as varied as searching for the perfect tree. How so? Well, just how big is a tree?

Here are 5 things to consider when sizing and selecting your on site power generator;


1) In order to determine the size of KW or KVA of the generator you need, first you have to determine the critical load (equipment) you need to be able to run in case of a utility outage. What loads are critical for you? Is there HVAC equipment or water pumping equipment? Do any of your critical loads require ancillary equipment to run properly? A server creates heat, so having the server on the generator, but not the cooling system is a recipe for disaster. Likewise, a well pump is great, but if you neglect the septic pump then it can get poopy real quick. Once you determine what is critical, then you can calculate the total wattage required. A general rule is to allow 25% above full load for growth and increased generator run time.

2) After you have calculated the required size, then you will need to consider the type of fuel that will be used to power the on site power generator. There are 4 common fuel types of generators; unleaded gas, diesel, LPG and natural gas. If you have storage or utility service of an alternate fuel on site, then it's a no brainer. If you do not, then you may need to consider a location for a fuel storage tank to support your generator. Most unleaded gas and diesel generators can be supplied with integral tanks that can be sized according to your desired run time based on the calculated load.

3) As your considering your fuel type, you should also start contemplating the electrical controls and start up functionality. On site power generation controls can range from very simple start up signaling on utility outage, all the way to very complex load shedding and load staging. The roll up generators that are manually started and connected to outlets or tap boxes are the simplest, but generally do not offer any automatic transfer options. If you need the generator to start and supply the load automatically when a utility outage occurs, then you will need an automatic transfer switch.

4) It's always a good idea to consider how you will fund any project. A generator brings peace of mind, while adding value to your home, office or mission critical environment. Here are a few price points that you might see on the East Coast. For single phase 120/240V residential types of systems, 18KW-22KW average size generator install, depending on fuel will run between $10-15,000. 6KW-8KW portable, aka roll around, running on unleaded will run between $4-$8,000. When you jump up to three phase 120/208V or 277/480V you should budget $1,000/KW, which doesn't typically drop off until you get up into 1/2 MW and above units.

5) Manufacturers matter, but keeping up with the maintenance will keep any of the top brands, Generac/Kohler/Cummins running. What's important when you consider a brand name is their service and support models. When you reach out to an electrician or generator sales rep, they will be happy to jump through hoops to give you their best service on the installation of the on site power generator. Hopefully they will continue the same level of service in 12 months when the unit is due for a $500 oil change and preventative maintenance service. If not, be prepared to go shopping for an alternate service provider who specializes in keeping your investment in peak, working condition. A little homework now finding some options, might pay dividends later.

Unity Power Services would be glad to help you with product selection, load sizing and turnkey pricing. We provide design-build electrical services, agnostic on site power generator sales and ongoing generator maintenance and repair.

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