The power output of a generator is measured in watts and before you purchase a generator you need to decide the size that will meet your requirements. If you will only be using a generator for occasional backup for lights and small appliances a side valve generator with a 2000 watt output will be adequate. For longer outages or for heavier use a generator with 3500 watt output or higher and overhead valve design will be needed. We've put together some information about features and output ratings to help you decide on the size and type of generator that will suit your needs.

Features

Valves - valves may be side mounted or overhead mounted. Larger models are usually overhead mounted and in general are more reliable and longer lasting.

Auto Shutdown - An automatic shutdown switch for low oil conditions is essential to prevent accidental damage.

Spark arrester - always ensure your generator has a spark arrestor if it will be used anywhere near combustible materials.

Pull Start - compression release pull starts make starting much easier

Generator Size

It is, of course, vital that you purchase a generator that is adequate for the intended load it will carry. You can calculate the wattage required for your particular circumstances very easily. Firstly decide what appliances, pumps, lights etc need to be run then look on the appliances for the wattage required for each. Don't forget any furnace/boiler or water pumps. Electric motors on pumps and other appliances require more wattage to start up than for running, sometimes up to three times as much so this must be taken into account when doing your calculations. In addition, if you have more than one motor, unless you can manually stagger their start ups, they will all be drawing start up power at the same time and put a bigger burden on the generator.

All appliances and motors should be labeled with their wattage requirements. Note down any that you are going to use with your generator. The following table is a rough guide to wattages in the absence of a label.

* Furnace fan 200
* Computer 150
* Television 450
* Fan 100
* Hot plate 1100
* small freezer 300
* Radio 120
* sump pump 450
* Refrigerator 2600
* water pump 250-2000
* water heater 5000

Add up all the wattages, not forgetting the start up wattage of your motors. The total does not include any safety margin so add 10% to the total figure. Now you have the information needed to choose the size of generator to purchase. Be sure to consider the continuous rating not the maximum or surge rating on the generator.

Types of Generator - Portable or Standby

Now you need to decide if you will purchase a portable or standby generator. A standby generator is fixed in position and permanently wired into the house circuit. It is usually fitted with an automatic switch to turn on when the power fails. A portable generator can be moved around and used on camping trips or for powering tools etc away from a power source. It can be used, with the correct add ons as a power source for your house in an emergency although it would usually need to be switched on manually.

Last, but definitely not least!

Always ensure that generators are installed by a qualified electrician and never hook up the generator to the house power outlets or to live power lines.

Run generators in open spaces never in enclosed spaces like basements or garages as they produce deadly carbon monoxide gas. It is a good idea to install carbon monoxide detectors to ensure you and your family are safe.