Hot Or Not? Is Thermal Efficiency Always The Right Answer?

There is increasing demand for higher efficiency gas fires and the industry has responded by developing products with some quite remarkable claimed efficiencies. However, the issue of efficiency is a point of confusion for many consumers as well as many in the industry. One of the main points of confusion is the difference in efficiency between gas and electric fires. Many consumers believe that electricity is the cleaner, cheaper option, while the industry itself usually claims that gas is more efficient. The truth is that they are both right, depending on the circumstances. What is all too often ignored is that different people buy fireplaces for different reasons, and efficiency cannot be judged out of context. The two main reasons for purchasing a fireplace are: 1. To provide a secondary heat source2. To provide a decorative focal point

Secondary Heating

If secondary heating is the main purpose of the fireplace then high efficiency gas fires are certainly the best option. Electric heaters are around 100% efficient at point of use, but considerable energy is wasted in the generation and transmission of electricity through the National Grid. To provide heat, its much more efficient to burn the fuel directly in the home. High Efficiency Gas fires now have the added advantage that they improve the overall energy efficiency rating of the home. For new homes, this can help to ensure compliance with building regulations, which now set Carbon EmissionTargets that are calculated using a method called SAP. The SAP calculation assumes that all homes have electric secondary heating unless an alternative is provided. Fitting a high efficiency gas fire is a cheap method of improving the SAP rating compared to the alternatives such as increased wall or roof insulation. The result is that house builders can create a decorative focal point for little or no additional cost. Similarly, existing homes being sold will soon need to be energy rated as part of the governments Home Information Packs scheme. There are no minimum standards set but the rating may well affect the value of the house, making a high efficiency gas fire a cost effective option. There are many different types of gas fire with varying degrees of efficiency. The industry’s reluctance to develop an accurate and universal efficiency test makes comparisons difficult. Glass fronted fires are generally most efficient because they reduce the amount of hot air that can be sucked up the chimney. Flueless fires eliminate any heat loss up the chimney but do require the installation of a permanent air vent, meaning that manufactures claims of 100% efficiency do not stand up in reality. The SAP method accounts for these factors and in most cases balanced flue gas fires produce the best carbon emission rating. To add to the confusion, many manufacturers advertise the Net efficiency of their products, rather than the Gross efficiency that is used in the SAP ratings. Net efficiency is always higher than the Gross figure, but is less accurate. Specifiers and home owners should always look at the Gross efficiency.

Decorative Focal Point

So what about those customers who mainly just want an attractive focal point? Should they even be concerned with thermal efficiency? Well, thermal efficiency will affect the home energy rating as explained above, but otherwise it is of little concern. The most efficient option for customers seeking a decorative effect is an electric fire. Although the heater is less efficient than gas, the decorative effect can be switched on without the heater. As a result the customer only uses the heater on the rare occassion that they need it. The rest of the time the decorative effect can used alone, consuming around 100W of electricity compared to 7000W of gas for a typical gas fire. The result can be very significant energy and cost savings.

Conculsion

In summary, high efficiency gas fires, especially balanced flue fires are the most efficient option for customers wanting heat and a high home efficiency rating, while electric fires are more efficient for customers who just want a visual focal point. The industry should take a wider view of efficiency and focus on meeting the consumers real needs. Most of the confusion surrounding efficiency is the consequence of an inward looking industry focussing on short term sales targets. What's needed is an industry with both vision and integrity. Accurate testing, honest marketing and consumer focussed product development would be in the long term best interests of both the consumer and the industry.

- Tom Greenwood

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