Frequently asked questions

Your solar thermal system uses sunlight to heat water for your home. Solar collectors absorb heat and transfer it to a circulating fluid, which moves the heat to a storage tank. This hot water is then available for taps, showers, and appliances. A backup heater ensures you always have hot water if solar heating isn't sufficient. The system is designed to run only when needed to maximise efficiency and prevent overheating.

The system operates automatically based on temperature differences:

• Turns on when the solar collectors are hotter than the water in the tank, ensuring efficient heat transfer.
• Turns off when the tank reaches its set temperature or when there isn't enough solar energy to heat the water effectively.

Your solar thermal system is designed to provide hot water year-round, but performance will vary with seasonal changes:

• Summer: Longer days and stronger sunlight mean your system will produce more hot water than in winter. Be mindful of stagnation and consider using more hot water during peak solar hours.
• Winter: Shorter days and lower solar intensity can reduce heat production. Your backup heating system may need to assist more during colder months.
• Spring & Autumn: Moderate sunlight means balanced performance, but cloudy days can still impact heat generation.

Hot water availability is determined from tank temperature measurements. These measurements form a range from minimum usable water temperatures at 0% to maximum temperatures 100%. The maximum temperature is tailored specific to your site by Senergy. We maximise the accuracy of hot water availability by installation of as many temperature sensors along your tank as possible.

Stagnation happens when your solar thermal system gets too hot because it's not using the heat it collects—common in summer or when you're away. This can cause pressure buildup and system stress.

How to prevent it:

• Use more hot water on sunny days.
• Activate "holiday mode" if leaving for a while.
• Ensure your system can release extra heat.

Your system is designed to handle this, but frequent overheating may need adjustments. This can be monitored from Senergy Cloud.

Solar works best when heating a cold tank. If the tank is already hot from another heat source (e.g. a gas boiler) before the sun came up, this limits the capacity for the solar collectors to produce any energy. It's important to use energy available in the morning — consider high-demand activities such as morning showers early in the day. This helps the system produce more energy through the day. Keep an eye on hot water availability metrics.

• Check for shading from trees or buildings that may change with the seasons.
• Monitor system performance via your app and check for any significant drops in efficiency.
• Increase consumption in periods with lots of sunshine — see overheating and stagnation sections.

A few tips to help protect and optimise your system during winter, involving frost protection and ensuring your collectors remain in the sun:

• Be aware of crisp, cloudless days that are common in winter — these can generate notable hot water so plan around this.
• Ensure pipes and collectors are properly insulated to prevent heat loss.
• Check for snow or frost buildup on collectors and clear if necessary.
• Use backup heating efficiently by setting it to only activate when necessary.
• Reduce hot water demand in the evening, as solar heating is strongest in the daytime.

On very hot days with little hot water usage, your system may reach high temperatures. Senergy have implemented controls as part of system design to ensure overheating is minimal — these may include night cooling, heat dump radiators, and expansion vessels. Even so, it's important to ensure your system does not stagnate by increasing hot water usage during peak solar hours.

No, your system will still contribute to heating, even on cloudy days. The systems are designed to handle winter conditions and should function correctly.

If you're away for a while, your solar thermal system may collect more heat than needed. This results in stagnation, and prolonged stagnation will degrade the system quickly. Action is not required but for best practice these tips can help:

• Enable "holiday mode" on your system controller.
• Use hot water before leaving to reduce stored heat.
• If away for a long time in summer, consider partially shading the collector or installing a heat dump.

Most systems manage extra heat safely due to Senergy's design. This relies on the system being well maintained through its life — the Senergy app aims to warn of any issues that can be detected.

Your solar hot water is mainly used for:

• Taps & showers — kitchen sinks, bathroom taps, and showers (unless your shower is electric — check before use).
• Washing machines — some models connect to hot water for energy savings.
• Dishwashers — certain models use hot water directly.

Most central heating systems (like radiators) don't use solar hot water unless designed to. Check your appliances or ask your installer to confirm what's connected.

Some washing machines can use solar hot water, but it depends on the model. Machines with a hot water inlet can be connected, reducing energy use. Check your user manual or ask your installer if your setup allows it.

Some dishwashers can use solar hot water, but many have built-in heaters and only take cold water. Check your dishwasher's manual — if it has a hot water connection, it may work with your solar system.

If your shower is connected to your hot water system, it likely uses solar-heated water. However, if you have an electric shower, it heats water independently and won't use your solar hot water. Check your shower unit or ask your installer if unsure.

This happens when the tap is far from the hot water tank, meaning it takes longer for heated water to travel through the pipes. Insulating pipes or installing a hot water circulation system can help reduce waiting time.

Like any system, you should maintain your system in line with installation recommendations. This means checking pressures to make sure they don't reduce, visibly checking for leaks, ensuring no leaves or sticks are on the panels, and taking steps to avoid stagnation.

Stagnation will degrade systems that have glycol (anti-freeze) in the heat transfer fluid. During stagnation, the fluid can boil, causing it to thicken, degrade and even damage seals. Frequent stagnation will mean that servicing needs to occur more regularly, in which the heat transfer fluid may need to be replaced.

Our data comes from multiple sources — simple measurements are performed by the solar thermal controller. Other data comes from calculations e.g. Hot Water Availability, this is calculated from measurement sensors available at the site therefore contain more error but remain useful approximations to help optimise your system. In simpler systems where the additional heating loops are not measured we estimate the contribution from the backup heating systems; this estimate is variable with site specific installations, but will provide a reference for how each system contributes to the available hot water. The energy calculations used within the app are not suitable for precise metering use cases.

Our system measures your system through the controller which operates your solar thermal system. This needs to send the information through the available internet connection to Senergy Cloud. If there are any longer periods of downtime in your local power or internet connection, data can unfortunately be lost. This can be seen by either gaps in the displayed charts or a message stating no data is available for the period.

It is very difficult to predict solar irradiation / sunshine levels due to cloud cover. In countries like Ireland and the UK, cloud cover can be sporadic, which has a notable impact on performance. Our weather data comes from WeatherAPI.com, which sources real-time information from thousands of public and private weather stations, and forecasts are based on the European Centre for Medium-Range Weather Forecasts (ECMWF). Local conditions can still vary due to microclimates or sudden weather changes.

We compare the measured solar heat energy in kWh against typical emissions of backup heating systems (e.g. gas and oil boilers). This data is obtained from reputable UK and Irish governmental organisations including the Consumer Council and SEAI. This is an estimate as the operating conditions of the alternative heating system cannot be fully modelled, but it should produce a fair estimate.

The savings calculations use the generated solar heat energy in kWh and compare this to the equivalent units of fuel required to achieve the same quantity of heat. The pricing of these fuels is updated using typical pricing across the UK and Ireland, obtained from reputable UK and Irish governmental sources. This remains an estimate as it will vary based on the condition and operating nature of the alternative backup heating system. This will give an indicative estimate of available free solar energy that has been produced over the course of the period viewed.

Our cloud platform collects data through the controller which operates your solar thermal system. This needs to send the information through the available internet connection to Senergy Cloud. If there are any connection issues with your local internet or power the system can go offline, and data will not be available.

Please restart your Senergy controller by turning the power to the system off and on again. This is typically wired to a plug — ensure both the solar thermal controller (white controller) and KM2 datalogger (green controller) are rebooted. If the device remains offline for another hour please contact Senergy for additional help.

Your personal data is securely stored and processed in line with data protection regulations. We only collect what's needed to operate your system and improve your experience.

• Data storage: kept on secure servers.
• Usage: used for system monitoring, performance insights, and support.
• Sharing: we share location data with a third party for weather forecasting purposes but do not share other personal data without your consent.

For more details, check the Privacy Policy in the app or on our website.