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Heat pumps & tariffs: Facts from the fuzziness

  • 11 hours ago
  • 4 min read

For the full list of articles demystifying heat pumps click here

The opportunity

Time-of-use tariffs reward energy users who can be flexible about when they use energy.


They encourage people to use more energy at times when it is cheaper and less when it is more expensive.


They are not new. For example, you may have heard of Economy 7 tariffs which provide cheap night-time energy for homes fitted with electric home storage heaters.


There is now a wide range of different time use tariffs. They offer great potential to reduce the running costs of a heat pump – anything from £200 to £750 a year for the average household.



The savings aren't automatic though and are trickier to achieve than many people realise.


"Simply switching" to a time-of-use tariff for a heat pump is unlikely to reduce energy costs and can easily increase them.


Understanding what you need to do differently with your heat pump is essential.


As the articles below explain, it is only possible to be certain you can make meaningful savings if:

  • The heat pump is controlled in the right way, and

  • It can perform some specific, rather cunning party tricks


Below I explain three different methods of using a heat pump with time-of-use tariffs, starting with the poorest method.

Three methods

Each method summary below has a link to a separate more detailed article on that method.


Depending on your existing knowledge of heat pumps you might want to skip through to the articles on methods 2 or 3.


Most homes use thermostats and time schedules in different ways to suit the different tariff costs at different times of day. This typically includes reducing the thermostat during expensive tariff periods.


The article on this method may disappoint or frustrate many people.



It explains why, with a few exceptions, savings using this method are far from certain or significant, and why energy costs can even increase. It is also a method that is likely to give the poorest comfort.


The article explains what you can do to give you the best chances of savings if you control your heat pump in this way.



This method firstly means using your heat pump in a very efficient way, something called "weather compensation" mode. All heat pumps can operate in this mode.


Used in this way some heat pumps can then do a party trick that is super helpful with time of use tariffs: They can modify the heating flow temperatures during different tariff periods, such as making the heat pump work a little harder during low cost tariff periods.



Unfortunately only some heat pump controllers can do this trick, such as some from Daikin, Vaillant, Viessman and Nibe. Dimplex ground source heat pumps can also do this trick.


You need to be a little geeky and do some experimentation using this method, but it is worth it.


This method gives a high certainty of cost savings and also better comfort than method 1.


There are a number of innovations now available that use sophisticated software to fully automate how heat pumps are controlled.


The software learns about your house and your comfort how they can best work with time of use tariffs. They even take into account what the weather forecast is for tomorrow.


These methods automatically give you the maximum possible cost savings while still giving you the comfort you want.


This way of controlling will become the norm in the future, but is available...now!


There are now many heat pumps that these innovations will work with which the article lists.


The compatibility list will only grow, and will progressively include control of home energy storage.

But where do batteries fit in?


These articles are aimed at helping the many households who do not have home battery storage.


You may see comments on social media that simply say "just fit a battery" if you want to use time of use tariffs with a heat pump.


Batteries are great, but they aren’t essential.


You can get great savings out of time use tariffs with heat pumps without batteries if you are able to use your heat pump in the right way.


Batteries are also not a practical or affordable option for many people, and it can take a long time for them to pay for themselves.


My advice would be focus on the basics first: Get your heat pump system working as well as you can with a time-of-use tariff, and only then consider batteries later.


If get the basics right, you may not need such a big battery, should you ever choose to get one.




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While I have made every effort to ensure that the information contained on this website is correct, I cannot take responsibility for errors or omissions.


All content on the site should be treated as information and not advice. You should take professional advice where appropriate to different site articles.


If you have any other suggestions for additions or changes to site content do please let me know.


Thanks.

Mark Thompson


Get Energy Savvy - simple practical home energy efficiency information

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