Perry is one of our earliest users at Havenwise. I’m pretty sure he is one of our first 5 users actually. Back then, I personally visited every user to set up Havenwise together with them. Luckily, today it’s 100x easier so homeowners can do it by themselves in less than 10 minutes.
Perry has a 11.2 kW Mitsubishi Ecodan heat pump. No batteries, no solar PV. His hot water consumption is above average, with a 7 person household. Before Havenwise, Perry would consume 4800 kWh of electricity per year on a fixed tariff to ensure his family has hot water when they need it.
Since using Havenwise, the cost of providing hot water for his family has plummeted. Perry is now on the Octopus Agile tariff, and Havenwise optimises the heat pump operation to meet the hot water needs of the family. Practically, Perry has set in the Havenwise app when he needs hot water. Havenwise makes sure that those requirements are met in the cheapest possible way. If Perry would decide to change tariff (which he did a few times last winter when the Agile prices were high), he just updates his tariff in the Havenwise app and Havenwise’s optimisation automatically adjusts - nice and easy.
The result? A saving of £179 in the past 2.5 months, or £861 annualized. That’s two-thirds (67%) of the energy cost, gone. This is achieved through a combination of reduced energy consumption and optimisation for Perry’s tariff. The table below shows the results.
When it comes to hot water optimisation, Havenwise has a few tricks up its sleeve.
Tariff: Havenwise automatically picks the cheapest moments in the tariff to heat the tank. Perry’s Octopus Agile tariff changes every 30 minutes and his tariff for the next day is published daily by Octopus Energy at 4pm. The tariff sometimes becomes negative as well, meaning Perry gets paid to consume electricity by his energy supplier. When that happens, Havenwise automatically heats the tank above Perry’s setpoint (“overheating”). That ensures Perry gets paid the maximum amount by Octopus, and it means less consumption will be needed when the tariff turns positive again. Double whammy. With all this clever optimisation, we realised an effective tariff of 15.27 p/kWh, a whopping 43% below the Ofgem price cap!
Hot water schedule vs reheat: Heat pumps by default often operate on a “reheat” mode for hot water. That means the heat pump will automatically reheat the hot water tank when it drops below a certain threshold. That threshold is typically between 40-50°C, depending on how the heat pump has been commissioned. The problem with this method is that the reheats happen when the tank is still at high temperatures, resulting in inefficient heat pump operation. Havenwise operates differently. We ask the user when they need hot water, and we then heat the tank in advance of these moments. That means the tank is typically emptier (i.e., has a lower temperature) when we start heating the tank. This results in a higher efficiency and lower energy consumption.
Warmest times of the day: Havenwise will automatically select the warmest moments in the day to run a hot water cycle. Warmer outside temperatures mean higher efficiency of the heat pump. Roughly, every 1°C increase in outside temperature is a 2-3% increase in heat pump efficiency!
Don’t run a cycle when it’s not needed: If we see that no hot water cycle is required to meet the comfort requirement of the user, we don’t trigger a hot water cycle. Pretty obvious, but often forgotten in default heat pump controls.
Holiday mode: When users leave on holiday, they switch on “holiday mode” in the Havenwise app. That means the tank won’t be heated until holiday mode is switched off. Again, pretty obvious but it’s often surprisingly difficult in default controllers to turn the hot water off, and therefore often not done, resulting in wasted energy.
Each of these might sound “simple”. But the trick is to do these in parallel, continuously, fully automatically, and without sacrificing comfort. Sounds easy, but it isn’t.
So can Havenwise make a difference during summer, when the heat pump is not heating but still doing hot water? Absolutely.
If you want to try out Havenwise for free, just go [here] and make an account
We provide controls and monitoring for heat pumps without the need for extra hardware. Homeowners enjoy maximum comfort and reduced energy bills, and installers save time with every install. Homeowners, start a free trial today! (then £50/year).
