What Size Generator for Gas and Electric Furnace?
We have covered in this post what size generator is needed to run a gas or electric furnace in your house. We have given you the computations needed to calculate the generator size yourself.
If one of your main justifications for buying a generator is to run a furnace, there are many factors to be taken into account including the generator’s size.
The starting and running wattage and size of that capacity as well as the power consumption of other devices determine whether or not a furnace can be run on the generator. You’ll run at the same time.
An 1800 to 2000 starting watts generator should usually be sufficient to power a gas heater with a modest blower fan, control panel, and little inducer motor. Large electric furnaces like 8KW or 10KW would need at least a 12KW to 13KW generator to cover the starting watts and amps.
Whereas an electric furnace needs power to run the whole unit, a gas furnace only needs it to power the inducer motor, draft blower fan, and control board.
What Generator Size Should I Run a Furnace?
You would have to determine how many watts your furnace draws before purchasing a generator mostly for it.
Most residential heating systems range from 3,000 to 5,000 watts normally. It means working at 20 amp at 240 V or 12 amps at a 120 V circuit.
Check the manual or specification sheet on the furnace to determine the simplest means to compute the furnace power need.
If the handbook indicates your furnace draws 20 amps at 240V, then the formula to determine the wattage is:
Watt = Volt x Amps
Watts = 240V x 20amp
Watts = 4800watts
That is only an inexact estimate. Let us be accurate. That calls for independent calculations for gas and electric furnaces because one operates completely on electricity and the other requires power to run. only the inducer motor, blower fan, and control board.
We will also have to estimate the power consumption of the blower draft fan.
Starting and running blower fan watts
Starting and Running Watts of Blower Fan
| Fan size | Starting watts | Running watts | Watt-hour |
|---|---|---|---|
| ¼ HP (0.25) | 1100 to 1200 | 350 to 400 | 0.4kWh |
| 1/3 HP (0.33) | 1700 to 1800 | 550 to 600 | 0.6kWh |
| ½ HP (0.5) | 2300 to 2400 | 750 to 800 | 0.8kWh |
| 1 HP | 4700 to 4800 | 1500 to 1600 | 1.6kWh |
Running watts may vary even though starting watts of the fans stay the same because they need some extra little bit of power to beat inertia to start. The running watt requirement could go to 20 to 30% if the fan runs at low speed.
A gas furnace calls for what size generator?
In gas furnaces, the blower draft fan uses most of the electricity; the inducer fan and control board come next.
Other objects like igniter, lights, and sensors need little energy to function. Let’s provide you with an example.
Q1. Assuming the inducer motor needs as little as 100W to run, suppose a ¼ (0.25) HP blower fan demands 1200 starting watts and 400 running watts. The gas furnace’s generator for a 0.25HP blower fan will be of what size?
Ans. Blower starting watts + blower running watts = 1200 + 400 = 1600
- The total power required by the inducer motor is 1600 + 100 = 1700.
- For your ¼ HP gas heater, you would need a 1700+ watts generator.
- Generator size blower fan
- HP 2000 W ¼ (0.25)
- 1/3 (0.33) HP ranging from 2500 to 3000 watt
- 3500 to 4000 watt ½ (0.5) HP
- 1 HP, 6500–8000 watt
An electric furnace demands what generator size?
Every component of an electric furnace—from the heating element, blower fan, and transformer to the control panel and circuitry—needs power to function.
To find out how many watts the heating element uses, you would have to examine the handbook. It doesn’t need starting watts because the heating element lacks a motor; but, the motor does.
Let me provide you with an example.
Q1. Operating an electric furnace’s heating element requires 5KW; a blower fan needs 1200 starting watts and 400 running watts. Which generator size is needed to power the electric furnace?
Ans. Beginning watts of blower fan + running watts = 1200 + 400 = 1600
- Add the heating element power requirement: 1600 + 5000 = 6600 watts.
- Operating your electric furnace would call for a generator with 6600 to 7000 watts.
- Electric Furnace (20KW) Blower Fan Generator Capacity
- 22000 watts ¼ (0.25) HP
- 23000 watt 1/3 (0.33) HP
- HP 24000 watt 1/2
From 27,000 to 28,000 watts 1 HP
Why Inverter Generators are Recommended for Furnaces?
Gas or electric home heaters need a clean energy generator. High harmonic distortion in your generator may harm the furnace as the power changes.
Honda EU2200i, Champion 2000W, and Westinghouse 2000W are a few instances of excellent inverter generators.
Will a Generator Harm My Furnace?
Variations in voltage might harm the electrical components of a furnace, notably a blower motor. Power fluctuations also lessen the efficiency of the furnace.