Problem Addressed

In the UK, heating water in the home represents a large percentage of total energy consumption and so much of this energy is wasted heating unnecessary amounts of water in old clandestine hot water cylinders. These cylinders waste energy, suffer high heat losses, take a long time to heat up to full and often have no way of utilising high yields of renewable power on the grid. They also offer no way of knowing what volume of hot water is inside, so often, they are manually boosted to full or are scheduled to do so often during the day or indeed to always maintain a full tank of hot water just in the eventuality the end user may or may not need hot water over the day. They also have no way of informing the user or building manager what the energy use actually is.

Furthermore, as the UK makes its transition to alternative heat sources to heat water and spaces, either industrially, commercially or in the home, current or older installed hot water cylinders don’t allow this transition to take place on the hot water side, meaning a replacement is required now or will be in the future depending on the accompanying choice of heating technology. As more renewable energy comes online in the UK, the current grid network is ill equipped to deal with it and requires more smart technology that can detect it and utilise it in the home, to be connected. This then means it’s not wasted at source as is the case currently (shut off) and can be used more effectively through smart time of use tariffs and savings passed to customers. Also, a larger percentage of locally generated renewable power should also be used on-site, in the buildings with solar PV for example.

Solution Overview

Mixergy smart hot water cylinders can volumetrically heat the water inside precisely to what is required, rather than unnecessarily heating a full tank every time, halving heat losses and reducing on site energy demand through heating potable hot water by up to 40%. All cylinders are future proofed to work with ASHP/GSHP technology & solar PV should the need arise and with time of use smart energy tariffs as they emerge, thus facilitating the change to lower carbon tech buildings either now or in the future without the need to replace anything.

The cylinders have an on-board AI machine learning tool that can assesses what volume of hot water is being used and when, and it simply prepares this amount (if the option selected) adopting the most economical way possible to heat the water required at the times it’s required i.e. using off peak/agile tariff use. Mixergy also offer a dual fuel AI system that switches the heat source automatically between gas/electric depending on cost.

Mixergy’s range of direct electric cylinders heat the water 5 x faster (direct – 2 x faster on gas) to useable volume by preparing only what is needed and cost far less to run. With both the indirect and direct cylinders, a reduction in required cylinder size is possible due to volumetric heating – great when there’s a lack of space in the plant area and for reduced embodied carbon in builds and quicker reheat speeds/less power. Systems all come with remote monitoring capability so any FM company, installer or end user can access data on energy consumption, cleansing cycles, smart schedules and more and can alter cylinder settings to reduce rollout maintenance charges and identify issues before they arise for the end user.

All cylinders are smart app enabled and have a free, intuitive app for each user to prepare schedules, adopt complete auto-energy saving modes or fully manual (for both tech savvy or shy of), access energy data and all cylinder functionalities. The cylinders are also designed to help balance the grid (if option selected) and harness more renewable power available through their DSR facility, acting like a giant virtual battery when linked together and automatically tracking greener power.

Mixergy now have official appendix Q status through BRE, associated with fully embedded solar PV diverter tanks that can absorb far more locally generated surplus solar export on site than standard PV to cylinder scenarios (30%-BRE qualified). With indirect (gas heated) PV cylinders, users can save up to 150kg/CO2/annum.

Benefits of the smart cylinders have been independently tested and qualified by: Energy Savings Trust (20% less gas used), National Physical Laboratory (Volumetric heating energy savings), BRE – appendix Q smart cylinder submission for improved SAP/reSAP/EPC scores, Centrica & Williams Advanced Engineering (our investors), Catapult, 30+ 5-star reviews from customers.

  • Prices range from £800-1000 (depending on variant) for 120L – 300L, direct & indirect standard smart cylinders. For the PV ‘ready’ option its: + £75. This option is the dual fed top immersion or connection to both grid and the PV diverter control unit (supplied by others). For the PVE (fully embedded solar PV diverter option): + £300. This option requires no third party diverter control box circa-£500. For the LTPHE (low temp plate heat exchanger for heat pump connection) option: + £245.
  • Installation & Maintenance: Installation for plumbing and electrics is the same as a standard cylinder (G3 qualified etc). There is the added wifi/app connection, but each cylinder comes pre-paired to an EOP switch ready to plug and play. Mixergy have also developed an installer app for use to commission and bring the cylinder online. Maintenance is the same as standard pressurised systems, annual check-up. The systems have the added benefit of remote diagnostics to reduce roll-out charges for customers.
  • Operating costs: Energy use for the cylinders will depend completely on how they are used by the user/what load profile and what tariffs they are on and what tech they have connected. Mixergy cylinders save on average 30% on our customers’ hot water bills over standard cylinders. Where PV is deployed, the systems can save up to £160/annum.
  • Warranty: 25 years
  • ROI: 5-8 years

Case Study

Ocean Group (Ocean Housing): As part of the BEIS funded ‘PETE project’, Ocean Housing offered their residents the chance to apply for a funded replacement Mixergy smart hot water cylinder. The primary aim of the project was to demonstrate a scalable domestic demand side (DSR) response offering. However, the project not only proved the mass-market viability of DSR, but also significant environmental and resident benefits. Mixergy’s smart hot water cylinders utilise machine learning algorithms to optimise heating schedules, only heating what is needed at the lowest possible cost. This allowed the users to minimize running costs, carbon and kWh’s.

The scope – 71 direct electric Mixergy cylinders were installed ranging in size from 90L-18OL. The takeaway results were:

  1. A 35% reduction in running cost from £125 to £80 per year. The average consumption per tank was 2.18kWh/day (as opposed to 4kWh national average).
  2. 16% reduction in carbon emissions equating to >50kg of CO2 saved per tank per annum of operation.
  3. 12% reduction in energy consumed by implementing our machine learning option (ML) when compared to a Mixergy cylinder running a normal ‘customer set’ timed schedule. The implementation of machine learning shifted energy consumption into off peak so that twice the amount of energy was delivered at less than half the price.

Carbon insight: The Mixergy cylinders were able to deliver hot water at a lower carbon intensity than a combi boiler: 183gCO2/kWh vs. 230gCO2/kWh

Facts and Figures

5-8 years

This page presents data, evidence, and solutions that are provided by our partners and members and should therefore not be attributed to UKGBC. While we showcase these solutions for inspiration, to build consensus, and create momentum for climate action, UKGBC does not offer commercial endorsement of individual solutions. If you would like to quote something from this page, or more information, please contact our Communications team at