Should I replace my oil boiler with a heat pump?
With many households now feeling the pinch of the cost of living crisis, in particular exceptionally high fuel prices, rural homeowners may be wondering whether now may be the time to switch from an oil boiler to a heat pump. In this article we take a closer look at oil boilers versus heat pumps.
How does an oil boiler work?
An oil boiler works by igniting oil in a combustion chamber. This produces hot gases that are then passed through a heat exchanger (usually a copper coil) to heat water. This heated water is pumped around the home to your radiators, taps and showers when it's required.
How does a heat pump work?
An air source heat pump works by extracting heat from the air outside of your home and transferring it to refrigeration coolant. The coolant is then compressed, which increases the temperature significantly; the coolant is then moved to the indoor unit of the heat pump, which then passes air over the hot coolant, increasing its temperature to accommodate the thermostatic call for heat inside the home.
Can I replace my oil boiler with a heat pump?
This is where things get a little more tricky and there are some key considerations to weigh up. Firstly, there is the question of whether the construction of your house makes a heat pump viable. Next, it is important to consider whether a straightforward like for like replacement is possible. Let us look at each of these issues in more detail.
Do heat pumps suit rural properties?
Truth told, the question is not about whether or not the property is a rural property, but more about its age and construction. Old buildings such as farm houses and cottages were not designed with passive heating in mind. They are typically poorly insulated and very difficult to retrospectively insulate to the standards needed for a heat pump to achieve reasonable efficiency. If you have a rural home that is a relatively new build and enjoys a high standard of insulation, a heat pump may be worth considering, but for many rural homes, it is unlikely to be a suitable solution.
Do heat pumps work the same way as an oil boiler?
This is where things get a little more complicated. The simple answer is no. A boiler will produce a lot of heat with a high temperature difference in a very short space of time. A boiler can thus work with radiators with a very high temperature. A heat pump, on the other hand, produces heat more slowly and with a smaller temperature difference. The low temperature of the heat pump means that the radiator (or ‘emitter’) needs to have a much larger surface area. Essentially, it is no longer a ‘radiator’ but rather a ‘convector’.
While in the end they create the same result, the fundamental difference in the way the two technologies work means that they require a different design setup when it comes to how the heat is delivered to the property.
What would I need to change?
A standard boiler system is typically designed to run at an average flow temperature of 70°C, while the temperature difference between the water going into the radiator and the water coming out of the radiator is 10°C. That is, the water goes into the radiator at say 75°C and comes out at 65°C, having given up 10°C.
A heat pump system, in contrast, should ideally have an average temperature of around 37.5°C and a temperature difference of only 5°C. Therefore the water goes into the UFH or radiator at say 40°C and comes out at 35°C, having given up 5°C.
So what does this mean for you as a homeowner? If you opt for a heat pump rather than a gas boiler, you will need to size the radiators and/or UFH pipe lengths very precisely. You will also need to be able to control the speed of the water in the circuit as well as the delivery of heat to the circuit. The balance is critical and not always possible in older 'energy hungry' rural properties.
The final word
In light of rising fuel prices, the idea of swapping your oil boiler for a heat pump may seem like the logical choice at face value, but the truth is that this is not recommended for most rural homes. You need to be aware that in an existing home you'll probably need to update your existing radiators and pipework, as well as your heat source. The total cost of switching over may far outweigh the benefits in terms of both initial outlay and overall efficiency. Although our advice is based on every individual property, we would generally recommend customers consider upgrading to the latest generation oil boiler.
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