Investigating the Cost of Your Existing Energy Use

Have you ever considered calculating the cost of your energy consumption? And why would you want to do this in the first place. Calculating your energy consumption is not as daunting as one would think. You do have to carry out an inventory of all your electrical appliances and home illumination.

This is an ideal task for a spreadsheet.

If we wish to use renewable energy for our home then it would be a good idea to know what our current energy usage is. Basically carry out an audit of your energy usage in order to establish a base point from which to calculate your load requirement for your solar panels and wind power.

Consider each appliance in your home and its energy use. Some appliances like kettles, toasters and the like draw a considerable amount of power when used but at the same time they are used for a relatively short time each day.

Once you know what your current energy usage is you can take steps to start reducing the amount of energy you use.

Estimating and / or timing the duration that each appliance and light is in use and the energy expended by each appliance and light is a real revelation. It allows you to make informed choices when buying new appliances or installing new lights.

For instance, I know that it's a lot less hassle to dry our clothing in a tumble dryer than on a washing line. However to dry a single load can take up to between 70 minutes to 140 minutes. Assuming that, as a family of four, you have on average of 7 loads in a week, therefore with a 3.3 kWh/cycle (my current tumble dryer energy consumption), assuming a 12-hour constant tumbling time per week, you will be using an approximate 2059.2 kWh a year. This costs currently around £186.77 per year.

I can probably save up to half the cost by putting the washing on the washing line and spend the money on myself instead.

One of the changes that is relatively easy to make concerns the illumination of your home.

When you consider the lighting within your home you should take the following into account:

- The general lighting of a room;
- Localised or task lighting i.e. concentrated light for activities such as reading, sowing and cooking; and
- Accent or mood lighting to create atmosphere or to focus attention on certain objects or areas.

For instance in parts of my home I initially reduced eight 50-watt lights to 25 watt and then reduced them even further to 2-watt LED lights. The LED lights outlast the 50 and 25-watt by a considerable margin.

A simple calculation shows the savings made by carrying out each of these changes:

Running the 50 watt lights for 3 hours a night I would be using 1200 watt hours per night i.e. 438 kWh per year.

Using the 25-Watt bulbs I automatically halved that.

However, with the 2 Watt LED light bulbs my energy use for this room has dropped to 17.52 kWh a year; a cost saving of £38.14 at current electricity prices i.e. £0.0907/kWh. It may not sound like much but you should consider that this was only for one room.

When replacing worn or damaged appliances they are replaced by appliances with better energy rating. I look at the energy rating of the appliances as well as the price when comparing new appliances. For instance I had to replace our condenser tumble dryer and I opted for a vented tumble dryer as there was a 0.5 kWh difference per cycle.

Each individual saving adds up in the end and over time can make quite a difference to your pocket.

Each small saving made this way reduces the load requirement of your renewable energy, which in turn means less solar panels, and energy storage requirements.


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Alain Prudhomme's interests include the various technologies that allow for the micro-generation of renewable energy for homes and the freedom such technologies avail the ordinary person. He also writes about the contentious and controversial issues surrounding global warming and climate change. You can find more resources at http://www.renewablehomeenergysolutions.com