Heater Buyers Guide

The Sealey Guide to Heaters

We offer an extensive range of heaters designed with various product features, such as adjustable output, portability, fuel tank gauge, automatic safety shut-off,  timer control, quick heating and quiet operation. Many of our models feature integrated thermostats to ensure energy efficiency and maintain an even room temperature. From portable, ceramic fan heaters, which achieve an instant odour-free heat ideal for home use, to Kerosene/Diesel Space Warmer® Heaters capable of heating well-ventilated areas up to 2500m3,  we have all environments covered.

There are two main measurements given for heaters, these are Wattage(W) or Kilowattage(kW) and BTU. A watt or kilowatt is a measurement of energy transfer. However, BTU, which stands for British Thermal Units, is the most common way energy and heat output is measured in the UK. Deciding which heater is required, based on your room size can be difficult, so we have provided a guide to help you:

Example based on the room being 4m x 4m.

4m x 4m = 16m2   |   16m2 x 111 = 1776W (Simply divide by 1000 to give you kW)   |   1776W x 3.41 = 6056 Btu/hr (Multiply by 3412 if using kW)

This is great for giving you a starting point. Remember these calculations are based on a ceiling height of around 2.5m. A significantly higher ceiling, or even poor insulation would require larger volumes of heat, so the wattage required would increase accordingly.

Heater Types

Once it is established what size heater is required, it is worth considering where and how the heater is going to be used. Below are some suggestions to suit various environments.


Convection makes use of air’s natural rise and fall to transmit heat, which is then transferred to the surroundings. It will warm a room evenly as the air rises and falls uniformly within the space. This type of heat is quick and responsive but once the unit turns off, the heat can soon be lost. It works best in small spaces but could aggravate dust allergies due to air manipulation.

Oil Filled

This type of heater contains oil, which is heated via an internal element. These are housed in a row of panels to maximise the heating area. The greater the surface area, the greater the transfer of heat into a room.


These utilise a ceramic element which has a metallic coating. The heat is created via resistance to electrical flow through the ceramic element. They create a heat similar to the heat of the sun. Any objects in front of them feel the benefit of the heat, but the air in between isn’t heated. Therefore, they are more efficient than traditional heaters that heat air and rely on air circulation to heat a whole room.


PTC heaters are used in a wide range of environments due to the safe, reliable and efficient heat they emit and the compact, lightweight design of the units. PTC materials restrict current flow as the threshold temperature rises. Initially, PTC heaters draw full power, enabling them to deliver a consistent, uniform heat quickly. Once the optimum temperature is reached, the overall power consumption level drops.

Infrared Quartz

Ideal for use at home and in office spaces, infrared heaters work by converting electricity into radiant heat. None of their heat is lost to air movement, as the radiant heat travels directly to objects. Once the thermostat is turned down, the room remains at a comfortable temperature due to residual heat.

Propane gas, paraffin, diesel or kerosene

Due to the fumes created, our range of Paraffin/Kerosene/Diesel and Propane heaters are used for heating large areas with a good source of ventilation, such as workshops, warehouses or barns, where external doors remain open for long periods. Deciding which fuel is best will depend on your needs.
Kerosene/Diesel burns strongly and offers a powerful amount of heat. This type of heater works by heating the air within the interior.

Energy Label

Energy labels like these are required on most electrical appliances, including some heaters. Appliances are tested for how much energy they use during typical use. This gives them a rating on a scale from A+++ to G, with A+++ being the most efficient.

ErP Regulation

ErP stands for Energy Related Products and is a regulation set by the EU/UK which is designed to drive improvements in the efficiency and performance of electrical appliances like heaters. All our ErP compliant heaters will feature the logo, clearly shown to the right.

Other Features to Consider:


This is an important factor where a dry atmosphere is important. Electric heaters could be suitable as they are less likely to create condensation. But if the area to be heated contains any gases or potentially volatile dust, specialised heaters must be used to prevent any risk of ignition. Sealey does not offer this type of heating.

Temperature control

Many heaters feature a thermostat. This allows you to set the heater to your ideal temperature. The heater will turn itself off when the temperature is achieved and back on if the room cools down. This helps to maintain an even room temperature and saves on wasted fuel.


Some heaters feature a timer control. This allows you to set the time the heater turns on, as well as how long it remains on for. This reduces the risk of leaving the heater on inadvertently, preventing wasted fuel and potential fire hazards.

Mains power supply

Electric heaters exceeding 3000watts, cannot be used on a conventional 13Amp mains power supply. If you plan to use a high wattage heater, you should consult a qualified electrician for advice.

Static or mobile

If you need to position your heater near to where you are working, or transport them to different locations, portable heaters are the ideal choice. Larger models are fitted with wheels. Otherwise, heaters that are wall mounted are the best choice. These are usually mounted above head height for improved safety. Heater output The larger the area to be heated, the greater the heater output needs to be. The output of a heater is often expressed as how many cubic metres it’s capable of heating. To calculate the output you require, multiply the height x width x length. This will give you the cubic size of the room you need to heat.

View our current range of Heaters here: