Heating the house is one of the main reasons why the electricity bill can go up in winter. There are many ways to do it and not all of them cost the same. Each method has its advantages, but clearly there are some considerably more energy efficient than others.

Here we leave you with a small comparison where we analyze the options we have, what their efficiency is and what their approximate cost per month is. Logically, these are approximate costs, since the price of electricity varies and we are also not going to take into account factors such as taxes or the different schedules.

What is COP? To differentiate some systems from others there is a piece of information that is very useful. This is the Coefficient of Performance (COP). This data allows us to compare which is the most efficient system. How does it work? It basically indicates how much useful energy a system produces, compared to the electricity it consumes.

If the COP is 1, it means that if a system uses 1,000 W of electricity, it produces 1,000 watts of thermal energy. That is, it converts all the electricity it consumes into heat. If the COP is 2, it means that for example for every 1 kW of electricity, it generates 2 kW of heat.

Electric radiators (COP 1). Electrically powered heaters usually generate heat by heating a resistance. They normally have a fluid inside that stores heat and distributes it throughout the radiator. And this in turn heats the air in the home.

The performance of the electric radiators It is moderate, having a COP of 1. Typically, they have a power of between 1,000 and 2,000 W in a medium-sized unit. This implies that to heat a room of about 20 square meters with a radiator of about 2 kW, we will spend around 2 kW for each effective hour of use.

This is not the most efficient method to heat the home, but it does have different advantages that make it a very widespread option. The first of them is that it does not require gas or emit odors. The second is that it is a method for heat up very quickly. Thirdly is the cost, since although the electricity bill is not the cheapest, it does not require such a high investment either.

Inverter or heat pump (COP 3-5). The other great alternative is to use the air-conditioningin its heat mode. In this case we are not heating a resistance, but rather we are taking advantage of the outside air to transfer heat from one side to the other. This is a more efficient process since the heat pump does not directly generate heat. This translates into a COP of between 3 and 5, depending on the model. That is, a heat pump consuming 1 kWh is capable of producing between 3 and 5 kWh of heat.

As we see, the air is considerably more efficient. Returning to the example of the 20 square meter room, an inverter with 2.5 kW of heating power will only consume about 0.7 kWh per hour at medium load.

🟢 A+++. Although the COP is used for quick comparisons, since 2013 the standard used is the Seasonal Coefficient of Performance (SCOP). It is a similar indicator to COP, but the difference is that SCOP uses a running average during different weather conditions throughout a season.

This coefficient is what defines the categories of energy efficiencies in inverters. In such a way that a heat pump with more than 5 SCOP has the A+++ label.

Aerothermal energy (COP 3-5). The problem with heat pumps comes from the use of gases. That is why the European Union is driving another system to heat our house, the aerothermaleven more efficient and much more sustainable, although with the problem that the initial cost is considerably higher.

Aerothermal energy offers an efficiency above 4 COP, which implies yields of 400%. It is considered one of the most efficient systems to heat our home and that is why your installation is on the rise.

Pellets, gas boilers and other systems (COP ≈ 1). We have described the three main methods, but there are many others. We have, for example, the natural gas boilers or propane. They are economical although they require a lot of maintenance and the performance usually remains below 100%. Something similar happens with the pellet stoves. Here the performance is usually around 90%. The problem in this case is that the fuel requires more expensive storage.

We also find alternative systems to electric radiators such as heat accumulators or underfloor heating. The performance of these is again close to COP 1, although the advantage is that they generate heat only at certain times of the day or in specific areas.

How does this translate to the invoice? To have a clear image of how much this can affect our electricity bill at the end of the month, let’s do some quick and approximate calculations.

We are going to take into account a cost of €0.20/kWh, which is approximately what is being offered today on average. We are also going to establish a demand of 55 thermal kWh per day, which is more or less the consumption necessary to heat an average house in winter.

Taking these parameters into account, here we leave you with a small table of the main systems:

As we see, heating our house with an electric heater is the most expensive system in terms of consumption. Using a heat pump reduces this expense by less than half. Even more efficient is aerothermal energy. Although, it is true that this table does not show the initial cost of the installation nor do it take into account many other parameters.

Image | Vije Vijendranath

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