Replacing a Navitron Solar Thermal System in Fareham

Back in the early days of renewables, Navitron was a major name in UK solar. The company trained installers across the country and built a wide network of subcontractors delivering solar thermal systems.

I was one of those subcontractors.

At the time, solar thermal was an excellent way to reduce the cost of hot water. For many homes it made good sense, and plenty of those systems are still working today.

This project in Fareham is a good example. The existing Navitron solar thermal system is not being replaced because it has failed. It is being replaced because the way households use energy has changed, and solar PV now offers much more flexibility.

The Existing Solar Thermal System

The property currently has a Navitron solar thermal system installed, and importantly there is nothing fundamentally wrong with it.

It still does exactly what it was designed to do:

• Heat the hot water cylinder efficiently
• Operate reliably when there is usable solar gain
• Reduce the need for conventional energy to heat water

That is worth saying clearly, because this is not a story about solar thermal being poor technology. In its time, it was a very effective solution.

The Main Limitation of Solar Thermal

The issue with solar thermal is not whether it can heat water. The issue is what happens once the hot water cylinder has already reached temperature.

At that point, the system has effectively done its job for the day and has nowhere useful to send any more energy. Even if there are still many hours of good sunshine left, the system cannot keep giving the household extra value in the same way that solar PV can.

In practical terms, that means:

• The cylinder becomes satisfied
• The solar thermal system becomes largely dormant
• Further solar energy cannot easily be used elsewhere in the property

That is where modern solar PV has a clear advantage.

Why Solar PV Makes More Sense for Many Homes Today

Solar PV generates electricity rather than just heat, and that makes it much more versatile in a modern home.

Instead of stopping once the hot water is heated, solar PV can continue providing useful energy across the day by doing things such as:

• Powering appliances and household electrical loads
• Reducing imported electricity from the grid
• Charging a battery for evening use
• Exporting surplus electricity back to the grid

So rather than the roof only contributing until the cylinder is hot, the customer can keep benefiting from solar generation throughout the day.

Still Using Free Solar Energy for Hot Water

One of the biggest benefits of switching to solar PV is that the customer does not have to lose the advantage of free solar-heated hot water.

By using a solar iBoost, some of the surplus electricity from the PV system can be diverted to the immersion heater in the cylinder.

That means the new PV system can still contribute free energy towards heating hot water, while also giving the customer all the added benefits of solar electricity for the rest of the property.

In other words, the roof is no longer limited to doing one job. Solar PV can support the home electrically first, and any spare generation can still be used to heat water.

A Shift in the Industry

This change reflects how the renewables industry has moved on over the years. Solar thermal had an important place in the early growth of renewable installations, but today households are using electricity in more ways than ever before.

With battery storage, smart tariffs, EV charging and more electrically driven heating technologies becoming common, solar PV is now often the more future-proof option for homeowners.

That does not mean older solar thermal systems were a mistake. It simply means that modern energy use now favours a technology that can do more with the available roof space.

This Fareham Project

For this customer in Fareham, replacing the existing Navitron solar thermal system with solar PV will make better use of the roof and provide more usable energy across the day.

The new setup will not only help power the home, but it will also allow some surplus energy to be diverted back into the hot water cylinder through a solar iBoost. That gives the customer the best of both approaches: solar electricity for the property and still the ability to use free solar energy for hot water.

This page will be updated with more information and images as the installation progresses.