Choose how your water is heated

The Mixergy app includes a setting that tells the tank how your home heats water. This is called the Heat Source setting. Choosing the correct option helps the tank use the equipment fitted in your home and avoids relying on electric backup heating when it is not needed.

What does “heat source” mean?

Your heat source is simply the equipment that heats your water. Depending on your home, this might be an electric heater inside the tank, a boiler, a heat pump or a combination of systems. Solar panels can also provide electricity for water heating in some homes.

Which option matches your home?

Electric

Choose Electric when the tank is heated by its built-in immersion heater, an electric heating element inside the tank. Some homes with solar panels also send spare solar electricity to this heater.

Indirect (boiler)

Choose Indirect when a gas or oil boiler heats the water through a coil inside the tank. Your boiler and Mixergy tank work together, but your room-heating controls are separate.

Heat pump

Choose Heat Pump when an external heat pump or a Mixergy iHP X heats the water. Heat pumps usually heat the whole tank more gradually than an immersion heater or boiler, so the percentage may rise more slowly.

Electric and Indirect (electricity and boiler)

Choose Electric and Indirect only when your system has been set up to use both. This is common where electricity or spare solar energy is used first and a boiler is available as backup. The two sources do not normally heat at the same time; the tank selects between them using your settings and the available energy.

Why does the correct setting matter?

• It helps the tank ask the right equipment to heat your water.
• It helps automatic schedules make suitable heating decisions.
• It can help the tank make better use of solar energy or cheaper energy periods, where available.
• It reduces the chance of the tank relying on the electric immersion heater when another heat source was intended.

If the wrong option is selected, the tank may still heat using electricity. You may therefore still have hot water, but the system may not be working in the way designed for your home.

How to check the setting in the app

You can check the selected heat source in the Mixergy app:

1. Open the app and select your tank.
2. Open Tank Settings.
3. Find Heat Source.
4. Check that the selected option matches the equipment in your home.

How to find out what heats your water

• Check any handover information supplied with your home.
• Look for a boiler or heat-pump controller near your heating controls.
• Ask your installer, landlord, housing provider or property developer.
• Do not open the controller, remove covers, touch wiring or change valves.

You cannot always tell how your water is heated by looking at the tank. Check your handover information or ask the person responsible for the system rather than guessing.

If you suddenly have no hot water

Do not try each Heat Source option to see which one works. First check whether the Mixergy Gauge shows any red lights and whether your boiler or heat pump has power. The gauge is the slim black panel with lights and buttons on the tank.

If you rent, contact your landlord or housing provider. Homeowners can use the relevant troubleshooting guide or contact Mixergy’s Homeowners & Residents team on 01865 595 875, Monday to Friday, 9am to 5pm.

Common questions

Do I need to choose a heat source when I move in?

Usually not. It should already have been set during installation. Check it only if you have been asked to, your heating equipment has changed or you think the setting is wrong.

Will the wrong setting stop all hot water?

Not always. The tank may fall back to its electric immersion heater. This can hide the problem, so ask for help if the setting does not match your home.

Can I use solar energy as the heat source?

Solar electricity normally works with the Electric or Electric and Indirect option, depending on how your system was installed. Confirm the correct choice with your installer.

Why does a heat pump look slower?

A heat pump heats water at a lower temperature and may warm more of the tank at once. The level can therefore rise more gradually even when the system is working normally.

Should I change to Electric if my boiler or heat pump has a fault?

Only if your installer, landlord or housing provider confirms that your system is designed to use the immersion heater as backup. Do not guess or change wiring or valves.

Related guides

Understanding heat sources

Using a heat pump

Using solar PV

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