How to heat a home? If central heating or individual gas or other fuel heating is not available, the most common solution in Spain is electricity. On the one hand, there are electric radiators of different types on the market, the best known are called blue heat and are cheap to buy and promise moderate consumption. However, as we will see, they do not reach the efficiency of heat pump systems.
The limitations of electric radiators
An electric radiator works by converting electricity into heat. Inside is a heating element, usually a resistance wire, which heats up when connected to electrical current. The radiator is filled with an oil or thermal fluid, which stores and distributes heat. The metal fins of the radiator in turn heat the air in the room.
These radiators heat up quickly, even more so in the case of blue heat radiators, which contain a more efficient thermofluid. Other advantages include their moderate price, their safety, since they do not require fuels such as gas and they do not emit smoke or odors.
They are also efficient because they convert almost all the electricity they consume into heat. That is, a 1000 W power radiator turned on for one hour provides 1000 Wh of heat. But this is not necessarily the best option.
The efficiency of heat pumps
Unlike radiators, heat pumps are not heating a heating element directly. A heat pump works by moving heat from one place to another using a thermodynamic cycle.
Initially the pump extracts heat from the outside air through the compressor unit located outside the house. Yes, even if it is cold outside, enough heat can be removed to cause the gas in the circuit to expand. The system compresses this gas using a pump, thereby increasing its temperature. The hot gas passes into the house where it heats the air, cooling, expanding, and returning to the outside through the circuit.
This process is efficient for both heating and cooling spaces, reversing the flow to extract heat from the house in summer, and functioning as an air conditioner. Heat pumps are more efficient than electric radiators precisely because electrical energy is not used to generate heat, but to compress a gas with the pump.
This means that for every unit of electrical energy they consume, they can provide multiple units of thermal energy. Their coefficient of performance (COP) is usually greater than 3 in energy classification A appliances, which means that for every kWh consumed they produce more than 3 kWh of heat. In other words, three 1000W electric radiators, with a total of 3000W, heat the same as a 1000W heat pump.
The drawbacks of heat pumps are the high initial cost compared to electric radiators: the initial investment can be high, although it can be amortized in the medium term thanks to the savings on the electricity bill. Another possible drawback is performance in extremely cold climates. Common heat pump air conditioning installations work well when the temperature does not drop below about 4ºC. For colder areas, it is necessary to install a different heat pump, with a gas that has a more efficient temperature range in cold climates.
Another drawback of these devices is the so-called thermal gradient. Hot air tends to stay in the upper part of the room, which can cause a feeling of “cold feet.” This can be mitigated with ceiling fans, reversing the rotation of the blades and therefore the air flow. Another, slightly more expensive solution is to purchase indoor floor units, which will however have the opposite effect in summer, producing a ‘hot head’ effect.
Thanks to its efficiency, which according to a MIT report can reach 400% in some cases, heat pumps receive subsidies in several European countries in an effort to reduce emissions and phase out heating boilers. However, in Spain most heating systems use fossil fuels such as natural gas. According to the gas sector represented by Sedigasreplacing the gas boiler park could have a cost greater than 200,000 million of euros. But for those who already have an air conditioning installation with a heat pump, the savings are instantaneous.
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