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Generator Guide - How to Choose a Generator

Are you a keen DIYer regularly taking on household projects? Or a professional tradesman completing large-scale jobs? Either way, a high-quality generator is often an essential piece of kit. Yet, with a huge range of models designed for different tasks, from powering workshops to computer equipment, it’s important to choose one that’s right for you. That’s why we’ve put together this handy generator guide, so you can find one that perfectly suits the task at hand.

What to look for when buying a generator

We understand that figuring out which generator to buy is no mean feat. There’s a huge range of options to explore, from 2 kW diesel generators to small petrol models, big generators for the home to those for sensitive equipment. Whether you’re looking for a model that can keep up on the jobsite, or the best generator for home use, we’re here to help. We’ve spent some time putting together a simple checklist of considerations, so you know what to look for when buying a generator.

  • Wattage – It’s important to consider wattage before you buy. You need to determine exactly how much power you’ll require for the items you wish to run.
  • Domestic or professional – Some generators are designed specifically for hobbyists and leisure use; others are perfect for workshops and commercial use.
  • Equipment – Do you want to run sensitive equipment such as computers or televisions straight from your generator? We have a range of inverter generators for sensitive electronics.
  • Petrol or diesel – You need to consider the total cost of ownership when investing in a new generator. With a comprehensive range of the best diesel generators and petrol models on the market, you’ll be able to pick the most cost-efficient fuel source for your power requirements.
  • Outdoor Use – You may want to use your generator outside for activities such as camping. Find out how you can tell if a generator is weatherproof and whether it's appropriate to use in wet conditions.
  • Standby & Specialist Generators – Do you want a back up power supply for your home? Or perhaps you need a specialist generator for industrial projects? Find out more about specialist and standby generators for home use.

Your total required wattage

Many people ask us “what size generator do I need?” The answer to this question depends on what it will be used for. All our models are rated to run at a certain wattage, so you must consider the amount of wattage you need your generator to produce. Regardless of whether you’ll be running camping equipment or a whole construction site, this is a vital step in the buying process – otherwise you might end up with a generator that isn’t fit for purpose.

Here are four key things to consider when it comes to wattage:

  1. You can find the individual wattages of an item on the equipment itself, in the user manual, on a manufacturer’s website, or by contacting the manufacturer by phone.
  2. What items do you want to run together? For example, if you want to run a slow cooker and a fan at the same time, you need the combined wattage of the equipment. If you’ll only ever run each item independently, then you just need to worry about the item with the highest wattage.
  3. Do the items have a starting wattage? Any piece of equipment with an induction motor will have a starting wattage, and therefore a higher wattage requirement. This includes chop saws, air compressors, vacuum cleaners, pressure washers, and freezers - anything with a motor in it. Simply multiply the item’s wattage by three to find its starting wattage.
  4. Give yourself some headroom. Just because your car can go 120 miles an hour, doesn’t mean that it’s suitable to drive at the maximum all the time. Your generator will be very much the same; a 4200W generator shouldn’t be used to power 4200 watts worth of equipment. Give yourself at least 20% head room.

So, what capacity generator do I need, exactly? Here’s how to work out what your final required wattage is:

All the individual equipment wattages for the items you wish to run together (x 3 if the item has an induction motor), + 20% head room = minimum wattage generator you require.

For example, to run a 250W slow cooker with a 650W hand drill the maths is:

650W (drill) x 3 (starting wattage) = 1950W

1950W (drill total) + 250W (slow cooker) = 2200W

2200W + 20% = 2640W total required watts required

To see how much wattage typical items use see our power ratings guide.

How do I convert between kVA, kW and watts?

Generators are often listed in kVA (kilo-volt-amps) or kW (kilowatts). These are both measurements of power, just in slightly different formats.

- To convert Watts (W) to KiloWatts (kW) divide by 1000 - Eg. 1000W = 1kW
   - To convert KiloWatts (kW) to Kilo-volt-amps (kVA) divide by 0.8 – Eg. 1000W = 1kW = 1.25kVA

Do you need a generator set for home use or professional use?

To make it easier for you to work out which generator to buy, we’ve split our range into two categories: generators for domestic use and generators for professional use. Each comes with its own warranty specific to its intended purpose.

If you’re searching for a high-quality diesel or petrol generator for home use, then an SGS generator will be ideal. Designed to be run occasionally, they are perfect for doing household jobs requiring power tools, as a short back-up generator for outages, or for working in the garden. Each of our SGS domestic generators are fantastic value for money and perfect for home and hobbyist use.

If you’re planning to use the generator every day or commercially, we have a wide range of exceptional models that are up to the task. Whether you need a power source regularly, or a long term generator you can use for extended periods of time, we’d suggest a Stephill generator. Renowned as some of the best generators made in the UK, each is designed to the highest of standards with energy efficiency and performance in mind. They’re fitted with HondaYanmar or Lombardini engines and come with a three-year commercial use warranty.

Domestic generators

3.75 kVA Portable Petrol Generator With Wheel Kit

Professional Generators

Stephill 6.0 kVA Yanmar Super Silent Diesel Generator

Do you need a generator for sensitive electronics?

If you need to power anything with a microprocessor, you’ll need to buy a generator for sensitive electronics. This is because these types of equipment are considered sensitive to electrical power and shouldn’t be run directly from a conventional generator. For instance, items such as computers, phones, TVs, games consoles, printers, DVD players and even some kitchen appliances and power tools will require a generator for sensitive electronics. One simple solution is to run them from an inverter generator to prevent damaging them. These generators "invert" DC power back into AC power, resulting in a much "cleaner" power (pure sine waves).

Hyundai HY2000Si

The Hyundai HY2000Si is one of the best small domestic generators in the Hyundai leisure range. At only 28kg, this petrol inverter generator is extremely lightweight and easy to transport, making it ideal for camping, caravanning or boating trips. The new improved design is smaller and lighter and has a brand-new digital display panel for simple, accurate usage.

Diesel vs petrol generator: Which is right for you?

If you’re looking at both petrol and diesel models, you may be wondering which generator to buy in line with your needs. We know that choosing between a diesel or petrol generator for home use or work may seem arbitrary, but in reality there are key differences that you need to know, so you can work out which will be best for you.

Firstly, you need to think about the upfront and long-term costs of each option, as they vary significantly. Diesel generators tend to cost more out of the box than petrol alternatives. However, over the long term, diesel will give you a considerable saving on fuel, especially if you have access to red diesel. Plus, diesel generators will generally stand up to regular use.

As a rule of thumb, it you’re looking for a generator under 10 kVA then you would purchase a petrol model. Over 10 kVa you would look at diesel generators.

Petrol Generators

Petrol generators offer great value for money and can be used either professionally or domestically. They typically are available in models offering between 1 to 10 kVA and in 110 and 230V sockets, so you would need a fly lead for a standard 3 pin plug.

Diesel Generators

Diesel generators tend to be larger and more expensive than petrol. However, they offer better fuel economy and longer run times. Big generators for home or domestic use are available  (10kVA+), such as "welfare cabin" models.

Can my generator be used outside in all weather?

There are many reasons why you might want to use your generator outside, for instance if you’re heading off camping. But it’s important to know that not all generators are suitable for all weather conditions. Here, we explain what weather protection each of the generators we sell have, and whether it's appropriate to use them in wet conditions.

SGS Generators

It is not recommended these generators are exposed to extreme elements. Please try and keep your generator protected from the elements, while ensuring ventilation is provided so you don’t cause a safety hazard or impede air intake.

Stephill Generators

You can use your Stephill generator outside, as the sockets on the petrol and diesel models are IP63 rated. IP63 is effective against:

  • 6 = No ingress of dust; complete protection against contact.
  • 3 = Water falling as a spray at any angle up to 60° from the vertical shall have no harmful effect.

While you can use your Stephill generator outdoors, it would be better covered.

Inverter Generators

Inverter generators have standard 3-pin plugs. Please do not use an inverter generator in the rain (SGS or Hyundai).

Standby Generators

There’s nothing more frustrating than a long power outage - waiting around in the dark, completely reliant on the National Grid. This is when domestic standby generators come in handy, providing power so you can use your household lighting and appliances. Being completely independent of the grid with a generator means you’re always prepared for a power-cut.

The simplest way of providing back up power to your home is to install two products; a standby generator and a transfer switch. There are two main types of transfer switches which we’ve explained below:

Manual Power Transfer – A manual transfer switch (MTS) allows you to switch between utility power and backup power at the touch of a button. They’re simple to use and relatively easy to install – the only drawback is that you might have to find the switch in the dark if you have a power cut at night!

Automatic Power Transfer – With an automatic transfer switch (ATS), the process is even simpler; the ATS senses when the power goes down and automatically starts the domestic standby generator. Within a few seconds, your home has power again and you can continue your day as normal. When the primary power for the home is restored, the ATS will switch back to utility power and shut down the generator. It will be left  in a standby state until needed again.

As well as providing you with convenience and security, standby generators for home use can reduce your home insurance rate and even boost the value of your house.

Beware: installing a standby generator and/ or a transfer switch should only ever be carried out by a competent electrician.

Specialist Generators

Here at SGS, we understand that everyone has their own unique requirements, which is why we stock a range of specialist generators. As well as our comprehensive range of petrol, diesel and inverter generators, we have LPG, welder, rail approved, welfare and export generators to suit more specialist needs.

LPG Generators

On average, LPG is 30-50% cheaper to run, and as the price of petrol and diesel steadily increases, an LPG generator becomes an ever more attractive solution. If you’ve got LPG gas canisters readily available, the LPG range can be a great mobile power solution.

Industrial Generators

These specifically designed diesel generators are great for powering accommodation or welfare units. They’re all made in the UK and powered by super-silent Yanmar and Kubota engines. So, those looking for the best cheap silent generators need to look no further. Their simple to use, single phase, low vibration units deliver straight to site.

Welder Generators

Stephill offer a small range of generators specifically designed for welders. They’re rugged, purpose-built generators made in the UK and are perfect for commercial use on site.  We also offer a range of compatible welding leads in AC and DC varieties.

Rail Approved Generators

Here at SGS, we’re one of the few suppliers of Network Rail approved generators in the UK. Designed to be robust, dynamic and incredibly safe to work with, these specialist generators are perfect for commercial use on and around the railway.

How to buy a generator

Wondering how to buy a generator? It couldn’t be easier with us. Head to our range of generators to explore the models we have available, including portable models, LPG fuelled options, light generators for the home and much more. If you have any questions, our in house experts are always on hand for buying advice and to provide bespoke care, regardless of the application.

Still need help?

Our in house experts are always on hand for buying advice and to provide bespoke care, regardless of the application.

Call SGS on 01332 576 850 or fill out our contact form today.