What Generator Size Do I Need?
The size of your generator depends on several factors such as:
How many people will live in the house. (If there are only one or two) How much electricity does each person use per day. (
If there are more than one) Will the generator run at all times when not being used for any other purpose? Will it be needed during power outages? Will it be needed if someone forgets to turn it off?
In general, the smaller the generator, the less energy it uses. However, larger generators may have higher operating costs and require maintenance which could increase its cost over time. If you want to save money while buying a small generator, consider getting a small unit with low running costs. You’ll still get good performance from such a unit since most of them are very efficient at converting electrical energy into mechanical work.
There are several types of generators available today. Each type has advantages and disadvantages depending upon the application. For example, a gas-fired generator produces less carbon dioxide emissions than a coal-fired unit, but it requires more fuel to operate. A diesel engine may produce lower noise levels than an electric motor, but it consumes more gasoline to generate the same amount of torque.
Diesel-Powered. These generators are most suitable for providing standby power for critical operations of any small business, in addition to providing light and heat in the event of a power failure. A diesel generator can also be used during a power failure so that your computer and other sensitive equipment don’t get damaged. But keep in mind that diesel generators require more maintenance than other types of units.
Natural gas-powered. These generators are best for providing light and heat during a power failure, and in many cases will also power your refrigerator. They won’t, however, be able to power your computer. One of these units can also provide emergency power during a blackout. A natural gas-powered unit is best for small offices with less than 10 computers.
Natural gas is cheaper than diesel fuel, and such a generator will also save you money in the long run.
Liquid Propane. These are best for providing emergency power during a power failure. They can also be used to power a refrigerator in the event of a blackout. A liquid propane generator is best for small businesses with less than 10 computers.
Note that liquid propane generators are very loud and may cause noise complaints from neighbors.
Natural gas-powered generators, on the other hand, run fairly quietly.
How much power do I need?
The amount of power required is measured in kilowatts or kW. A kilowatt is equivalent to 1,000 watts. Your energy usage in watts can be found on your electric bill. You will probably have two numbers, one for peak watts and one for off-peak. The number of peak watts is the maximum amount of power your home will use at any given moment. The off-peak number is the average amount of power your home will use over an hour. For example, if you have a total electrical load of 3500 watts and your rate is $0.40 per kilowatt hour, your cost per month will be $105. You can also determine the monthly cost by dividing the total wattage by 1000 and multiplying by $0.04 (or 40 cents).
If you want to find out how many watts various devices in your home use, check the label on the back or bottom of the unit. It will usually say something like “350 watts max.” You can then multiply this number by the number of units you have to get the total watts (or energy drain) for that device. For example, if you have 4 televisions in your home that each draw a peak of 350 watts, the total energy drain is 1,200 watts or 1.2 kW.
One kW will run a hot water heater or an entire office of 8-10 computers. If you have a home office with a desktop computer, printer, scanner, two monitors, and a laptop, you will need at least 3-4 kW to run all of these items. You will need more if you also have a refrigerator and/or a sump pump.
You need to add the number of watts for each device in your home that you want to run during a power failure (excluding motors, which will be explained later). This total is the minimum amount of kW you need. For example, lets say you need 3.5 kW. You can get this by using one 6 kW generator or two 3 kW generators.
NOTE: You may have an electric water heater. If you have a gas water heater, it will not need to be plugged into the generator. If you have an electric water heater and need to know how much power it uses, read the rating plate (on the bottom) to find its wattage. Then use this number for the calculator below.
Choose a generator that will provide at least as much power as you need. The generator’s size is measured in kilowatts, kW.
Enter the number of devices that need power.
(Ex: 2 electric water heaters total 9.5 kilowatts)
How much will this generator cost to run per month?
Assuming 12 cents per kWh, a 4 kW system will cost $48 per month to run continuously.
How much will this generator cost to buy?
A 6 kW generator can be purchased for around $1,500. How big is the generator (in kW)? Note: One kW is equal to 1,000 watts.
What else do I need?
Unless you already have them, you will need to get extension cords and several electrical outlets as well.
How much does it cost to buy these?
Prices will vary depending on what type you buy. Generally, outdoor rated, heavy duty, industrial strength cords can be had for under $10 each. Standard indoor house outlets can be purchased for around $1 each.
How many do you need?
The number of extension cords will be determined by how far away you need to place the generator from the house (or other structure). Each cord will need at least one outlet to run the devices in that area. For example, a simple 400 watt space heater requires 0.5 kW. If you have a 100 foot long, 16 guage extension cord with three outlets on it (0.33 amps per outlet), you could run 4 of these space heaters end to end.
What type of electrical outlets do you want to use?
Unless you have a lot of money to spend, we recommend using the standard indoor house outlets rather than the heavy duty or industrial grade outlets. These are easier to find and cheaper as well (about $1 each vs. $5 or more for the other types).
How long do you want it to be?
The longer the cord, the more voltage drop you will experience. Most small appliances (up to about 1.
Sources & references used in this article:
- Site specific optimization of rotor/generator sizing of wind turbines (KA Martin, MF Schmidt, SV Shelton, SW Stewart – 2007 – asmedigitalcollection.asme.org)
- A micro electromagnetic generator for vibration energy harvesting (SP Beeby, RN Torah, MJ Tudor… – Journal of …, 2007 – iopscience.iop.org)
- Interviewer effects in measuring network size using a single name generator (PV Marsden – Social networks, 2003 – Elsevier)
- Double-output induction generator operating at subsynchronous and supersynchronous speeds: steady-state performance optimisation and wind-energy recovery (I Cadirci, M Ermiş – IEE Proceedings B (Electric Power Applications), 1992 – IET)
- Inet-3.0: Internet topology generator (J Winick, S Jamin – 2002 – eecs.umich.edu)