What size generator do I need? (Generator Size Guide)

Buying a generator can be a daunting task with millions of different options available to you. Some questions you may ask yourself are: What fuel type should I go for? What oil shall I use? And even, How do I start the generator? Here at Generator Pro, we aim to make the process of buying a generator as simple as possible so today we are going to tackle the subject of: What size generator do I need?

First Things First…

If you are reading this article then you probably have an idea of why you need a generator, you probably have a list of appliances you want to power. But the question you need to ask yourself is: what items do you want to power simultaneously? For example, you may have a luxurious campervan which has an electric cooker, television, microwave and washing machine. However the chances are you won’t be using all these products at the same time.

Checking the Power Label

Now you have a good idea of what you want to power, you now need to work out the wattage the appliances require. All appliances sold in the UK will have a sticker similar to the one shown above outlining an approximate power consumption of the product. Add these values together for the appliances you want to run simultaneously and use this as a guide for your needed power consumption.

What if I can’t find the sticker?

All appliances are different so if you cant find a sticker on the product itself, we would always advise googling the model number. If you are unlucky with your search and still cant find a power rating, here is a rough idea of the power consumption of different products:

Appliances:

	Approximate Starting Wattage	Approximate Running Wattage	240V required?
Refrigerator or Freezer (Energy Star)	1200	132-192
Microwave Oven
650 watts	1000	1000
800 watts	1300	1300
1000 watts	1500	1500
Incandescent Lights	as indicated on bulb (i.e. 60W)	as indicated on bulb (i.e. 60W)
Furnace Fan, gas or fuel oil
1/8 Horsepower	500	300	Y
1/6 Horsepower	750	500	Y
1/4 Horsepower	1000	600	Y
1/3 Horsepower	1400	700	Y
1/2 Horsepower	2350	875	Y
Television
Tube type	300	300
Flat Screen (20”)	120	120
Flat Screen (46″)	190	190
Coffee Maker (4 cup)	600	600
Dishwasher (Cool Dry)	540	216
Electric Fry Pan	1500	1500
Electric Range (8-inch element)	2100	2100	Y
Automatic Washer	1200	1200
Clothes Dryer (Electric)	6750	5400	Y
Radio	50 to 200	50 to 200
Sump Pump
1/3 Horsepower	1300	800	Y
1/2 Horsepower	2150	1050	Y
Window Air Conditioner (10,000 BTU)	2200	1500
Computer
Laptop	200-250	200-250
Desktop	600-800	600-800
Monitor (LCD style)	30	30
Printer	400-600	400-600
Hot Water Heater	4500	4500	Y
Garage Door Opener	1420	720

	Approximate Starting Wattage	Approximate Running Wattage	240V required?
Television
Tube type	300	300
Flat Screen	120	120
RV Air Conditioner
11000 BTU	1600	1010
13500 BTU	2800	1800
15000 BTU	3300	2000
RV Refrigerator	600	180
Blender	850	400
Electric Grill (tabletop)	1650	1650
Slow Cooker	170-270	170-270
Hair Dryer (1600 watts)	1900	1800
Microwave Oven (650 watts)	1000	1000
Coffee Maker	600	600
Radiant Heater	1300	1300
Laptop computer	200-250	200-250
Satelite Receiver	250	250
Radio	50 to 200	50 to 200
Two-Way Radio
12A	360W	360W
23A	840W	840W
35A	960W	960W
Fan (portable)	120	40
DVD Player	350	350

Power Tools:

	Approximate Starting Wattage	Approximate Running Wattage
Air Compressor
1/2 hp	1600	975
1 hp	4500	1600
Bench Grinder (8 in.)	2500	1400
Circular Saw (Heavy Duty, 7 1/4 in.)	2300	1400
Concrete Vibrator
1/2 hp	840 (avg.)	840 (avg.)
1 hp	1080 (avg.)	1080 (avg.)
2 hp	1560 (avg.)	1560 (avg.)
3 hp	2400 (avg.)	2400 (avg.)
Demolition hammer	1260 (avg.)	1260 (avg.)
Drain cleaner	250 (avg.)	250 (avg.)
Drills
3/8 inch, 4 amps	600	440
1/2 inch, 5.4 amps	900	600
Electric Chain Saw (14 inches, 2 hp)	1100	1100
Hand Drill (1/2 in.)	900	600
High-pressure Washer (1 hp)	3600	1200
Rotary hammer	1200 (avg.)	1200 (avg.)
Table Saw (10 in.)	4500	1800
Industrial Motors
Split Phase
1/8 Horsepower	1200	275
1/4 Horsepower	1700	400
1/3 Horsepower	1950	450
1/2 Horsepower	2600	600
Capacitor Start Induction Run
1/8 Horsepower	850	275
1/4 Horsepower	1050	400
1/3 Horsepower	1350	450
1/2 Horsepower	1800	600
3/4 Horsepower	2600	850
1 Horsepower	3000	1000
1 1/2 Horsepower	4200	1600
2 Horsepower	5100	2000
3 Horsepower	6800	3000
4 Horsepower	9800	4800
Capacitor Start Capacitor Run
1/8 Horsepower	600	275
1/4 Horsepower	850	400
1/3 Horsepower	975	450
1/2Horsepower	1300	600
3/4 Horsepower	1900	850
1 Horsepower	2300	1000
1 1/2 Horsepower	3200	1600
2 Horsepower	3900	2000
3 Horsepower	5200	3000
4 Horsepower	7500	4800
Fan Duty
1/4 Horsepower	1200	650

Miscellaneous:

	Approximate Starting Wattage	Approximate Running Wattage
Electric Fence, 25 miles	250	250
Milk Cooler	1800	1100
Milker (vacuum pump, 2hp)	2300	1000
Portable Heater (kerosene, diesel fuel)
50,000 BTU	600	400
90,000 BTU	725	500
150,000 BTU	1000	625
Battery Charger
15 amp	380	380
60 amp with 250-amp boost	1500/5750	1500/5750

The Final Steps

So now you know what size generator you need and are ready to find the perfect generator for you. We would always recommend getting a slightly larger generator then what you need to make sure you are protected incase you decide to run something else on it. For example: if your calculations estimate that you will need 2200W then maybe look at a 3000W generator. This will also help with fuel consumption and limit stress on the generator saving you money in the long run. You can search for the perfect generator on our website, filtering by Generator Output. If you have any questions then feel free to contact us directly or check out our frequently asked questions album on our Facebook page.

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