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What’s the best electricity tariff for a heat pump?  

Our case studies page gives feedback from customers who have installed air source heat pumps and one of the questions we are often asked is Which electricity tariff is the best one to use with a heat pump? This isn't straightforward to answer. There are many different kinds of heat pump, and there are a lot of electricity tariffs in the market to choose from. The best tariff should help you minimise running costs but it shouldn’t constrain how you or your heat pump uses energy.

Here are some things to consider based on observations from our field trials:

  • Most heat pumps are designed to be left on all the time. The heat pump will vary its energy consumption based on the outside temperature and the temperature you’ve set your thermostat inside to operate efficiently. This is called weather compensation - more energy is consumed by the heat pump when it’s colder outside. Because the heat pump is adjusting its energy consumption based on these changes in temperature, the consumption can occur at different times over the course of the day and not in typical ‘peak’ or ‘off-peak’ periods.

  • A lot of people use night ‘setback’ temperatures whereby they set the temperature inside to be a few degrees lower when they’re in bed. This means the heat pump may not need to consume as much energy at night

  • Because of the points above, a tariff such as Economy 7 with ‘off-peak’ periods at night will usually not lead to lower heat pump running costs and may lead to reductions in the efficiency of your heat pump if you programme it to run in these hours  

  • Specialist tariffs such as Economy 10 would still require the heat pump to be programmed to run during the designated ‘off-peak’ periods, and it is very likely that the heat pump would need to work outside of these periods to keep your house warm when the weather outside is very cold. Energy in these ‘peak’ periods can cost a lot more so you can end up worse off in the long run
  • Data from our field trials suggests that the best tariff for minimising heat pump energy costs is a single rate tariff. These tariffs also mean the operation of the heat pump is not constrained. Some single rate tariffs allow you to fix your price into the future, typically one to three years. These are good if you want certainty for budget planning but they probably won’t represent the cheapest short-term deal
  • Another consideration is when to heat your hot water. A heat pump will either operate in space heating mode or hot water mode and not both at the same time. Depending on how you use hot water, it could be beneficial to programme the heat pump to heat your hot water during the day in summer wherever possible. At these times you shouldn’t need any space heating and the temperature outside will be high, which should increase the efficiency of the heat pump. In winter there will be a lot of time where the heat pump will need to provide space heating during the day. In these periods it is better to try to avoid heating your hot water as this could mean the heat pump needs to use a back-up heater, which could increase your energy cost, or the internal temperature might not be maintained whist the water is being heated. You should speak to your installer about how you use hot water so they can explain how to run your heat pump to match these requirements in the most efficient way
  • In summary, be sure to tell your installer how you like to heat your home and when you use your hot water and they should set up your heat pump to match these requirements. If the heat pump has been designed correctly you shouldn’t need to do much more than turn your thermostat up and down and possibly set your hot water on/off times to match your occupancy patterns. This is something you can now do remotely using HeatSmart® by EDF Energy . All of the major energy suppliers offer single rate electricity tariffs and you should review these to find the best tariff for you - there are price comparison websites if you need any guidance. EDF Energy’s current Blue+Price Promise is a competitive single rate tariff and is powered by low carbon electricity. Based on data from our field trials, the annual cost of running an air source heat pump in a 3-bed semi-detached house would be £697 Based on an annual electricity consumption of 5732.76kWh over the period 01/09/12 – 31/08/13 by the heat pump, back-up heater and immersion heater using a unit rate of 12.16p/kWh for the South East using our Blue+Price Promise tariff.


Air source heat pump installation

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EDF Energy ASHP Case Studies

During my last count there are now over 400 different air source heat pumps (ASHP) on offer in the UK and registered on the microgeneration certificate scheme

So, I can fully understand the challenge faced when thinking about a renewable heating product. Add the vast amounts of technical data and the frequent use of jargon, it can make it difficult to understand the technology and know which solution is the best for your home.

It’s also important to understand the experiences of others who have been through the process for you to realise you are not alone.

Hopefully the following will help?

We have now launched two new videos from one of our field trial installations, which will hopefully provide some useful insight on installing an air source heat pump.

​​The first video is an overview of the technology including the key elements of installing the ASHP and removing the old boiler system (don’t worry we will not be showing the full 2-3 days, just the key parts)

The second video is a customer perspective from our trial customer Rod, who has kindly provided his insight. This includes his thoughts and concerns prior to the installation of the heat pump, and also how he is feeling 3 months on from the installation.

Our ASHP trials: 

We have been running field trials of air source heat pumps since 2010. As part of our testing of various air source heat pumps we have installed in a variety of different situations, locations, size of houses and varying ages of properties. This has helped us to develop a very clear understanding of the requirements for retrofitting ASHP’s in a variety of different situations in the UK.

The trials have enabled us to review and highlight products, which from our experience offer the best combination of performance, reliability, ease of installation and use in the home.

Hopefully, our advice and experience of different installations will help provide you with the confidence to seriously consider an air source heat pump when replacing your assisting heating system. 

My final piece of advice is to do your research now, an air source heat pump is a considered purchase, and waiting until your old boiler breaks down on a cold winter’s day is not when you want to start Googling seasonal performance factors!

Author: Mark Amos

EDF Energy Innovation and Product trials


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