Wednesday, 30 December 2015

Lower Gas Bills in Winter: Reflective Foil on Radiators: How to Calculate Gas Usage for a New Condensing Boiler

In order to try and keep the heating bills to a minimum this year, and, in an effort to keep warm I have decamped in to one room for the winter months, where I now sleep, sit to watch the television, and, work at my computer when required.  The reasoning for this is so that I can switch off the redundant radiators in the rooms I am not using.  This has effectively left me with the boiler heating four radiators.  Two in the bed / sitting room, one in the hallway, and, one in the bathroom.  Fortunately when I cook in the kitchen, the heat generated by the appliances manages to adequately warm the room.

To monitor the cost of my bills I have set up a spreadsheet to record the value of the gas and electricity readings on a daily basis, along with the times that the heating is on.  My current utility tariff which does not expire until September 2017, see me paying 3.263p per KWh of gas, 11.687p per KWh of electricity, in addition to a standing charge of 19.13p per day for each service.

From my analysis the current cost of running the gas central heating for the four radiators is on average 15p per hour.  This is with the boiler set on the minimum setting as at the moment the weather has been relatively mild.  It should be noted that the cost for the first hour is higher averaging around 25p, due to the fact that the boiler has to initially work harder in order to heat the cold water / air up.  This means that for six hours a night the central heating gas bill is 90p.

In an effort to squeeze out all the available heat from the radiators in the bed / sitting room, where I spend the most time I have bought some of those reflective foil sheets which slip behind the radiators.  The reason I didn’t make these out of normal tin foil, was because I read that after a while normal tin foil reacts with the heat and air, and, loses the ability to reflect the heat.  Although the installation of the reflective radiator sheets did not lower the cost per hour of the boiler, it did feel as if the heat was distributed more evenly around the room, resulting in a more comfortable environment.  I installed the reflective sheets so that the top part protruded above the radiator, and, was angled to try and push the hot air into the room instead of letting it rise directly to the ceiling.  At the moment this is a bit unsightly, however, I am more about keeping as warm as possible than the aesthetics!

Another device that interests me is the Radfan.  This is a product which sits on top of the radiator, and, using the heat generated blows the hot air inwards in to the room.  The theory is that instead of letting the hot air just rise upwards to the ceiling it is more evenly distributed, and, leads to a more comfortably heated room.  The marketing literature associated with this product states that the fans only cost around £2 a year to run.  I can fully see the benefits of this system, and, how it may work, however, I am not yet fully convinced how long it will take to recoup the initial investment of £40 for the device.

The other thing I also considered was whether to replace my current non condensing boiler (15 years old, energy efficiency rating E of 77.2%), with a new condensing one (energy efficiency rating A of 90%).  The reasoning behind this is that the newer condensing boilers are more efficient at heating the water through recycling waste heat, and, therefore use less gas.  However, in calculating the figures I found out I would only save around £46.40 a year, which would take over 30 years to recoup the cost of the installation (£1,500) for a new condensing boiler!  It must be said though that this calculation is based on my gas consumption of 10,000KWh per year, which is quite miserly by all accounts.  The calculation for anyone that is interested is as follows.

Multiply the efficiency of your current boiler (77.2%) by the KWh of gas used on your bill (10,000KWh).  This gives the value gas you would have used if the boiler had been 100% efficient. 72.2% x 10,000KWh gives 7,720KWh.

Divide the 7,720KWh calculated in the previous step by the efficiency of the new condensing boiler (90%).  7,720KWh / 90% gives 8,578KWh.  This is the amount of gas you would use with a new boiler as opposed to the 10,000KWh for the old one.

Therefore with a gas tariff of 3.263p per KWh, the current boiler gas cost is 10,000KWh multiplied by 3.263p, totalling £326.30, and, the new boiler gas cost would be 8,578KWh multiplied by 3.263p totalling £279.90.  The saving in the gas charge each year for replacing the boiler is therefore £46.40.  Obviously if you increased your usage the savings would be greater, but even doubling your usage would still take over 16 years to recoup the cost of the boiler.


Anyway I shall leave it there for now.  I will continue to record my usage, and, let you know of any developments.

As always feel free to comment.

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