Fothermo photovoltaic 1kW heating element in boiler and hot water tank

With the 1 kW solar heating element from Fothermo (MPN: ROD-1000), you can easily convert your existing hot water tank to solar power. Simply screw the photovoltaic heating element into the standard 1.5" thread. From now on, you’ll use solar energy to heat your water and will no longer have to rely on expensive gas or oil heaters. It offers continuously adjustable power control from 0 to 1000W. With the convenient surplus function, you can route excess electricity to a second heating element or feed it into your home’s electrical grid using a small micro-inverter. This helps you save on your hot water and electricity costs. Another advantage is that you don’t need to register the system, since it doesn’t feed directly into the public power grid.

The benefits at a glance:

• 0–1,000 W continuously adjustable heating power
• For hot water storage tanks up to 500 L
• Patented MPP tracker for maximum output
• Up to 3,000 W PV connection capacity
• Direct DC power usage
• Innovative surplus power feed-in
• Maximum temperature protection
• Supports heating systems
• Easy installation—plug and play
• No registration required
• Made in Germany

Solar-Powered Hot Water

The solar heating element is a simple and affordable solution to supplement your heating system. You simply screw it directly into your existing hot water tank, effectively lowering your energy costs. At the same time, it reduces the load on your heating system or heat pump. The heating element is ideal for tanks up to 500 liters. It features its own temperature sensor and a freely adjustable maximum temperature of 65 °C (or 85 °C for limescale-free water). If there isn’t enough solar energy, the heating system’s temperature sensor ensures that the system automatically kicks in to provide additional heat. This way, you always have hot water, even in winter.

Utilizing Excess Energy—Thanks to an innovative switching function, you can flexibly use excess photovoltaic power. As soon as the maximum water temperature you set is reached in the storage tank, the system automatically switches over. This allows you to either use the excess electricity for additional solar heating elements in a cascade configuration or feed it into your home’s electrical grid via a micro-PV inverter.

Cascade Connection—You can connect two solar heating elements in series, one after the other. This ensures that the hot water in the storage tank is stratified particularly efficiently. As soon as the upper heating element reaches its maximum temperature, the system automatically switches to the lower one, which is located deeper in the storage tank and continues to heat the water there.

Grid Feed-In – Once the hot water tank has reached its maximum temperature, the system can automatically switch to a micro-PV inverter. This allows excess solar power to be utilized easily and without additional bureaucratic hurdles. This not only reduces hot water costs but also further lowers overall electricity costs.

Who is the solar heating element suitable for?

The solar heating element was developed specifically for smaller households with 1 to 4 people to significantly reduce hot water costs. It complements your existing heating system—whether gas, oil, pellet, or heat pump—in hot water production.
Example: With just three photovoltaic modules, a two-person household can generate almost all of its hot water using solar power during the summer months. Over the course of a year, the modules provide about 75% of the energy needed for hot water production.

Retrofit via Plug & Play

Installation is a breeze. The photovoltaic heating element is simply screwed into the standard 1.5"-flange of your existing hot-water storage tank, and the PV modules are connected in parallel using simple plug-and-play MC4 connectors. The heating process begins immediately, and since there is no complicated wiring and the voltage level is below 50 V, no electrician is required for the installation.

Performance data display:

• Voltage – Input voltage of the solar modules
• Power In – Input power of the modules
• Power Out – Output power
• Heating Energy—energy used for hot water production
• Output Energy - Total energy delivered
• Maximum temperature

Technical Specifications:

• Continuously adjustable heating power: 0–1000 W
• Max. voltage: 50 V (max. open-circuit voltage)
• Recommended PV module power: 38–43 V (MPP voltage of the PV modules)
• Max. input current: 23 A, automatic current limiting
• Max. connected power: 3,000 W
• Recommended connected PV power: 1,500–2,500 W
• Water temperature range: 5°C–65°C
• Max. output power: 1,000 W
• Threaded connection diameter: G 1½ inches
• Protection rating: IP20
• Weight: 0.9 kg
• Heating element length/immersion depth: 315 mm / 295 mm
• Unheated heating element length: 50 mm
• Dimensions: 468 x 140 x 154 mm

Package Contents

1x 1000 W solar heating element
1x User Manual
2x pairs of solar plugs