How Much Coal Do I Need for the Winter?

Leaves are beginning to change colour, the nights are drawing in; it’s Autumn. It’s time to restock the coal shed, build up the wood store, and order enough fuel to get you through the cold part of the year. You can still buy smokeless coal for heating online, and collect or receive delivery in Wolverhampton, but how do you know how much coal to order?

Can I still buy coal for heating?

The law changed in May 2021 to restrict the sale of traditional or household coal. This is coal which produces high levels of soot and particulate matter that is 2.5 microns across (PM2.5), small enough to enter the bloodstream. PM2.5 is a highly dangerous pollutant for human health, and these laws are designed to reduce air pollution and improve the health of the general public. Burning wet wood is also known to produce this dangerous soot.

The restrictions mean that:

  • It is illegal to sell bagged traditional house coal in units under 2m3
  • All manufactured solid fuels, such as briquettes, must have a low sulphur content and emit small amounts of smoke
  • Sales of wet wood in large volumes must include advice on how to dry the wood before burning


Is Smokeless Coal Any Good?

Smokeless coal is just as good as traditional coal

Calculating The Right Amount Of Smokeless Coal For Heating

If you’re using coal for heating, you’ll want to make sure you have ordered the right amount to avoid running out in a cold snap. This depends on the type of coal you’re using and how much heat is generated during burning.

However, the formula isn’t one-size fits all. You also need to take into account:

  • House size: The bigger the space you’re heating, the more coal you’ll need. You can choose to just heat one room to save fuel, but its important to understand how heat travels through your home
  • Insulation: If your house is well insulated, you won’t need as much coal to heat it as you would if there are drafts or cold-bridges. Good insulation traps heat in the house for longer, but if you have gaps under your doors, single glazing, or an uninsulated loft, you could be losing heat quickly and require more coal.
  • Weather: in the Midlands, we generally have milder winters than Scotland and the North, but not quite as mild as in the South. For people living in cold regions, more fuel is needed to keep the home warm. It’s also worth looking at the long-term forecast for the season, as this can give you an indication of how much coal you’ll need.
  • Heating system: While an open fire is convenient, it is less efficient than a coal boiler or stove. You will need less coal if you are using a more efficient heating system.

Understanding Coal Consumption

The quick way to consider how much coal you will need is to think about how many fires you will want to light. As a general rule, 25kg of smokeless coal can provide anywhere between 4 and 8 fires.

If you’ve got the time, calculating your coal consumption is a fairly easy mathematical equation.


1. Calculate the size of the space

This is easier if you have the plans but an approximation will be fine. Measure the width, length and height of the room you want to heat. This will give you the volume of air in the room

If you want to heat the whole house with your coal fire, measure the width and length of the interior, as well as the height of upstairs rooms and the height downstairs. Multiply width x length x upstairs height and width x length x downstairs height and add these figures together. If you have a single-storey extension, add this separately.

Width x Length x height = space in m³
e.g. 5m x 4m x 2.5m = 50m³

2. Work out how many units of heat you need

To heat the room or house to the desired temperature. In these cases, this is measured in British Thermal Units or BTU, which is a standard used for describing the heat output of different systems. 1 BTU = 0.0003kw.

Typically, UK homes with double glazing require 80-135 BTU per cubic metre to heat a room to 20-21oC. Those with single glazing need 136-165 BTU for the same temperature.

Room size (m³) x 135 = BTUs needed
E.g. 50m² x 135 = 6750 BTU

3. Choose your coal

Manufactured smokeless coals can produce approximately 5kw or 17,060 BTU per kg, while burning anthracite coal gives off around 9.2kw or 31,390 BTU per kg, and is also low in PM2.5s.

Find the heat output of your chosen fuel on the coal merchants’ website or elsewhere online.

4. Calculate how many days 1kg will last

To do this, you divide the BTU/kg of your chosen coal by your BTU value from step 2.

BTU/kg / BTUs needed = days
E.g. 31390 BTU/kg / 6750 BTU = 4.7 days

If you’re using anthracite to heat a small space of 50m3 as in our example, you will need just over 200g of coal per fire to get the room up to temperature. 1kg will likely last 4 days, accounting for topping up the fire and keeping it going.

5. Calculate your required coal for the winter

Of course, you’ll probably start heating before December 1st, so when we say winter, we’re including late autumn and early spring. The heating season typically runs from 1st October to the end of March, which is 183 days. Divide this by the number of days you found a kg would last in step 4 to see how many kg of coal you need for the winter.

183 / Days = total coal needed (kg)
E.g. 183/4 = 45.75kg

It’s advisable to over-order, just in case the winter is particularly cold or the season is extended. We suggest adding at least 5kg extra, but there is no limit to the number of orders you can place, so if you’ve underestimated your consumption, you can order coal online.


Choose Efficient Fuel And Reduce Costs

It is important to choose the most efficient and appropriate fuel for your needs. Anthracite coal burns hotter and longer than most manufactured smokeless coal and is compliant with Smoke Control Orders and new coal sales legislation.

At Charles Swann Coal Merchants, you can order open-sack and pre-bagged coal to be delivered in bulk anywhere in the Wolverhampton area. We supply a wide range of quality solid fuel options and are always happy to advise on the best fuel for your system.


Charles Swann (Walsall) Ltd
Old Landywood Lane
WV11 2AP

Contact Information

Phone 01922 408 152
Fax 01922 711 350

Copyright © 2023 Charles Swann. All Rights Reserved.

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