How to maximise efficiency levels and bring down running costs

One of the main differences between a boiler and a heat pump is that a boiler delivers the same temperature consistently to the home, whereas a heat pump will modulate its flow temperature according to the outside air temperature. The colder it is outside, the warmer the radiators will be inside.

Often heat pump owners swapping from a boiler to a heat pump take at least a year to get used to the way a heat pump works.

An oil/gas boiler effectively blasts heat into a home using a high temperature for a short period of time model. A heat pump is almost the opposite of that, producing a lower amount of heat delivered over a very long period of time, which is what makes it so efficient.

Often the first year of owning a heat pump can have mixed reviews with homeowners complaining of rooms hotter than others or cold spots around the property. 

The main reason for the temperature being incorrect comes down to how well you can evaluate the heat loss of a building, as it's this heat loss that determines what the flow temperature of a heat pump is set to.

The current heat loss calculations are reasonably good at determining the transmitted heat loss, this is the heat that physically transfers through the fabric of the building, but ventilation heat loss comes with its own challenges. 

One of the most important factors, along with a good level of insulation, is the heating capacity of the heat emitters. Larger heat emitters can transfer the same amount of heat energy at a lower LWT, hence the heat pump will operate more efficiently. At the heat pump end of the equation, the outside air temperature is important as far as the operation of the heat pump is concerned, but probably more important from the point of view of the heat loss of the home.

Big radiators, underfloor heating, and larger pipes are ideal, and increased home insulation is the best solution when it comes to reducing heat loss, so make sure your home is as well insulated as it can be. 

However, when reducing air leakage, good ventilation is required. Because as humidity changes so does our perception of heat. With higher humidity we often need higher room temperatures to feel warm. Lower humidity equals lower room temperatures and therefore more efficient heating.

Things have moved on in the heat pump industry in the last few years and the new refrigerants have much lower global warming potential. Not only are they better for the environment, but they can also reach higher flow temperatures, which means that you can heat your hot water to a higher temperature.

It also means that if you cannot feasibly change your radiators or central heating pipework, then a high temperature heat pump could still be an option, even if it is at a slight efficiency loss.

Keep your heat pump running around the clock with set back temperatures at night 

One of the first lessons that air source heat pump owners learn is that it costs less to keep your heat pump running all the time, day and night than it does to turn it off and on. Air source heat pumps have a lower flow temperature (the temperature of the water that they pump through your system) than gas boilers, which makes them much more energy efficient. They’re designed to keep your home at a constant temperature rather than pumping out a lot of heat quickly. You'll save very little money by turning an air source heat pump off for a few hours. Instead, you'll force it to use more energy, working harder to get your home back up to temperature. Set your thermostat to the temperature you want your house to be, and then leave your heat pump running to keep it that way. If you prefer a cooler home at night, you can set your heat pump to drop the temperature for a few hours.

One of the first changes that many air source heat pump owners notice is that their radiators no longer get as hot as they used to. This is another result of the slow and steady way that a heat pump warms your home. Gas boilers overshoot by pumping much more heat than you need into radiators for a short space of time and then leaving them to cool. If you struggle with sinus congestion or asthma, you'll be familiar with some of the side effects of this constantly changing temperature and the very dry air that it creates. Overly hot radiators don't make for a healthy environment.

Air source heat pumps are much more efficient because they warm your whole home to the temperature you actually want without wasting energy. It’s like the difference between the tortoise and the hare in the old fable, and we all remember which approach works best. With an air source heat pump, you won’t be able to warm up your hands quickly by holding them close to the radiator. On the other hand, you won’t need to. You'll probably find yourself breathing more easily too.

Hot water tips 

Air source heat pumps don't just give you more control over the temperature of your home. They also give you much more control over the temperature of your water. Traditional boilers often deliver hot water at a temperature close to 70°C, which is hotter than you can actually use. You end up having to add cold water, wasting both water and energy and adding to your bills.

Set the water temperature for your air source heat pump to between 48°C and 50°C, and you’ll have water at the right temperature for a bath, shower or sink of dishes while saving money. Your heat pump will run a weekly cycle that heats your stored water to 60°C to kill any bacteria, and the rest of the time it will get on with delivering your water at the temperature you really want.

Try not to turn radiators off– let your rooms keep warm together

Often I find rooms in customer houses with radiators turned off, mostly in rooms that are used for storage. After all, it doesn’t make sense to pay to heat a room with nobody in it. However, this approach won’t really work with an air source heat pump, which is designed to keep your whole house at a comfortable temperature.

If you turn off radiators in certain rooms, you’ll throw out the balance of your system. Asking your heat pump to heat fewer rooms than it was designed to causes it to shut down more often, which makes it harder to maintain a constant temperature, and can end up using more energy. This is exacerbated by the way that the cold walls of one room start to cool the rooms next to it in a domino effect, increasing the workload.

It seems counter-intuitive, but the most energy-efficient (and cost-efficient) way to heat your home with an air source heat pump is to warm all of it. As an added benefit, you won't end up shivering when you need to go and retrieve something from one of your cold, unused rooms.

Use weather compensation settings to save money on bills

You can set up your air source heat pump to respond to the temperature outside so that it increases the flow temperature of your system when it’s colder and reduces it when it’s warmer. 

Experimenting with your compensation settings on the air source heat pump keeps your home up to the temperature you’ve specified on your thermostat without using more energy than it needs to on warmer days. Different heat pumps have different types of weather compensation settings. I can set these to ideal figures for you on the service and show you how to adjust them.

Don’t take your heat pump on holiday with you. 

If you’re going away for a break, you might be tempted to give your heat pump a holiday too. However, I would advise against turning it off completely. Your heat pump will need to use more energy getting your home back up to temperature than it would keeping it warm while you're away. If you wait to turn your heat pump on until you walk back through the door, you'll have to wait to be warm while it catches up.

Heat pumps warm homes more slowly, but much more efficiently and it's almost always best to leave them running. The best approach is to leave them on normally if you're away for the weekend, and turn them down or use a holiday setting if you're gone for a week or more. Set your heat pump to return to normal running two or three days before you get back.

Following all the advice above should result in getting the best out of your heat pump resulting in a warm cosy house and low energy bills.