What Size Generator Do I Need to Run a House?

October 4, 2024 | Nate Cord

From what appliances you need to power to the size of your home, this guide covers how to determine what size generator you need to run your house in the case of an outage.

Why You Need to Choose the Right Size of Generator to Run a House

Selecting the right size generator for your home is crucial. A generator that is too small can overload, causing damage to your appliances or the generator itself, and fail when you need a power source during outages. An oversized generator, on the other hand, might lead to more fuel consumption and much higher costs, which might not be required. A properly-sized home generator will provide consistent and reliable power during outages, without unnecessary costs and consumption.

What Appliances Need Power in Your Home?

The first step in determining the generator size is knowing what appliances you need to power. Every appliance has two power requirements:

1. Starting Wattage: The higher power required to start appliances.
2. Running Wattage: The power needed to keep the appliance operating after it starts.

Running and starting watts requirements differ for every appliance, and some appliances require no surge power (starting watts) to turn on.
To calculate your total power requirements, list all appliances you want to run, write down the starting and running wattage, and add up both to find the capacity you require.
For a house, you can often assess the power requirements of the distribution board in your house, which tends to operate at a voltage of 230V and a capacity of 100 Amps. Covering this power demand, for instance, would require a generator with a capacity of 23kW (230V x 100A = 23,000W = 23kW), which can provide electricity to the entire house.

A power calculator can also help with this step, by determining the continuous power rating you require when you add up all of your essential devices. To help you get started, here’s an idea of the starting and running watts of typical household appliances:

Appliance	Wattage (Running)	Wattage (Starting)
Refrigerator	1200	200
Freezer (Chest)	1600	400
Freezer (Upright)	2200	500
Microwave (1000W)	1000	1000
Toaster (2-Slice, 1000W)	1000	1000
Dishwasher (1200W)	1200	1200
Washing Machine	2400	1200
Space Heater (1500W)	1500	1500
Television (LCD, 42″)	120	120
Computer (Desktop)	300	300
Laptop	250	250
Ceiling Fan	60	60
Light Bulb (LED)	—	10
Light Bulb (Incandescent)	—	60
WiFi Router	20	20

We would recommend that you choose a generator that is slightly bigger than your needs. This way, you get extra watts, so the generator won’t be running at full load (which is quieter), and you can account for any additional appliances in the future.

What Size Is Your House?

Generally, the larger a home, the more watts it uses. For small to medium homes, a 5,000 to 10,000 watt generator should be sufficient. For large homes, you may need a generator rated at 20,000 watts or more to cover your entire energy consumption – in particular, if you have air conditioning and heating systems to run.

The average UK household between 2-3 people uses 2,900 kWh of electricity per year., but this can vary wildly depending on your family’s habits. Here’s our recommended generator wattage for different house sizes to provide whole-house backup.

 

House Type	Suggested Wattage
Small Caravan	1,500 – 2,000W
Studio or Flat (1 Bedroom)	3,000 – 10,000W
Small Home (1-2 Bedrooms)	5,000 – 10,000W
Medium Home (3-4 Bedrooms)	15,000 – 20,000W
Large Home (5+ Bedrooms)	20,000W

In addition, keep in mind that any unique circumstances will impact the size of the generator you need.

Climate: In colder climates, you might need more power for heating, and in warmer climates, you might need air conditioning to run.
Length of Outage: If you expect prolonged outages, you may need a more comprehensive backup generator.
Energy Efficiency: Homes with energy-efficient appliances may have lower wattage requirements.

Types of Generators for Houses

Depending on the size of the generator you need, most people tend to use a portable or inverter generator to power their house.

Portable power stations are smaller, more affordable generators that can be moved around as needed. They generally provide power for essential appliances and are best suited for short-term outages.

Inverter generators are ideal for running sensitive electronics, use less fuel and make noise. However, these tend to have less power than standby models. That said, many inverter generators can be paralleled together to double their available amps if/when needed.

If you experience frequent power outages, you might be best with a standby generator, which powers an entire house. In the event of a power outage, these standby generators can be turned on with a manual or automatic transfer switch to keep your home alive.

Fuel Types

Generators run on different fuel types, including petrol, diesel, propane, liquefied petroleum gas (LPG) or solar power. Diesel is the most popular fuel for industrial generators as it’s effective, cost-efficient and readily available. However, natural gas generators produce less emissions and have more affordable running costs.

Solar generators are ideal for those who wish to avoid fuel altogether; although the initial cost for a panel can be more expensive, solar pays for itself in the long run by making it so you don’t need to pay for future fuel. It is the most eco-friendly option.

Noise Levels

One factor that’s often overlooked when purchasing a generator is the noise levels, in particular in residential areas.

Generally, larger generators produce more noise. If your home requires a high-power generator, expect higher noise levels unless you invest in a quieter model.

The noise level is measured in decibels (dB), and a typical generator can range from 60 to 100 dB. To give you an idea, 60 dB is about the level of normal conversation, while 100 dB is akin to the sound of a chainsaw. If noise is a concern, silent generators are your best bet.

To recap then, to calculate your generator needs, you should:

• Make a list of essential appliances.
• Calculate starting and running wattages.
• Consider the size of your home.
• Add a safety margin (usually 10–20% more than the total wattage).
• Determine the type of generator that best meets your needs, considering your power requirements, fuel types, and required noise levels.

FAQS

Can I Run My Whole House on a Portable Generator?

While portable generators are convenient and less expensive, they typically aren’t designed to power an entire house. Most portable models provide around 3,000 to 7,500 watts, which can run essential appliances but may struggle with larger loads.

Can a Battery-Powered Generator Run a House?

A standard battery-powered generator can run essential appliances like lights, small refrigerators, and electronics, but may struggle with high-demand systems. Some high-end battery systems, like the Tesla Powerwall, can power a whole house, but the upfront cost is significant.

For extended outages or larger homes, battery-powered generators may not be the most practical solution unless paired with solar panels or used in combination with a traditional fuel-powered generator.

Looking for a quality generator? At Generators Direct, we offer a range of generators, power stations and power banks for your specific needs. All of our products are manufactured, tested and certified to industry standards, and come with a price promise – you won’t find prices cheaper anywhere on the web, but if you do, we’ll match them. In addition to this, all orders come with free mainland UK shipping and after-sales support from our experts.

If you require additional advice or have a question for our team, don’t hesitate to get in contact with us using this form or via phone at +441639849847.