News Twitter You Tube

Mailing list

If you would like updates on Energeno & Wattson please click here

Hot water from your Solar PV system


It can be challenging to find ways to maximise your home-grown electricity consumption. Optimmersion® is an automatic controller that diverts all your surplus generated electricity to heat water in your immersion tank. Investing in an Optimmersion® system for use with solar panels will pay for itself in as little as 11 months, and will bring you savings on your energy bills year after year.

Once the cost of system has been paid back, you will see years of profit ahead of you in the form of lower energy bills. The Optismart bonus refers to additional savings made simply by being aware of and controlling your home’s electricity consumption, using the Wattson energy monitor.

What people are saying about Optimmersion®

“I knew the system would be efficient when I chose to install it, but I never guessed how fantastic it would be in terms of saving energy and money”

Steve Davies, Newport

“I haven’t turned the hot water on since my Optimmersion® was fitted!”

Stella Woods, Milton Keynes

“Since we installed our Optimmersion® we can’t believe how much we have already saved! In November alone we saved £20 in oil bills because we used our own generated surplus electricity to heat our water tank. We were able to check the figures using our Wattson.”

Jill & Tony, Cambridgeshire

Product information

Optimmersion is a proportional controller that diverts surplus electricity to heat water in the immersion tank. It only uses surplus electricity – electricity that is not being used in the house, so it is effectively giving you automatic hot water.

Optimmersion graph

Optimmersion® versions

All versions are supplied with a controller unit and a power throttle, part of the modular design. The controller unit needs to be accessible as not only does it become your controller, but it shows useful information about the performance of your system.

Optimmersion® Wireless OIMM-WIEN-UK

Optimmersion® Wireless allows for standardised, predictable and repeatable installations thanks to the wireless connectivity between power throttle and controller. The informative display shows generation values, how much is flowing to and from the grid and your household’s usage. You also see how much surplus is being diverted to the tank. Optimmersion® Wireless includes multiple timers, to allow you to use off peak tariffs and a boost period. Optimmersion® Wireless can cater for multiple tanks in either shared or cascaded formats. And if you already have a Wattson display, it will work with that too.


Optismart® Hot Water allows for standard, predictable and repeatable installation thanks to the wireless connectivity between the controller unit and the power throttle. It has multiple timers allowing for use of off-peak tariffs to ensure the homeowner is getting the best possible rate for heating water. The colour display shows how much electricity is being generated, used and how much surplus is being diverted to the tank. Optismart® Hot Water can cater for multiple tanks in either a shared or cascaded formats. The incorporated Wattson technology means that homeowners can add an Optiplug to continue to make the most of their generated electricity once the tank is full.

How it works

Optimmersion® is a proportional controller to add to a Solar Power installation. It diverts any surplus electricity to the immersion heater when surplus power is available.

Simple to install, it supplies variable power depending on the excess electricity being generated. It automatically harvests surplus electricity and all of it is used to heat water and maintain temperature level.

It is installed between the immersion tank element and the mains, no modification to the existing immersion element, hot water cylinder or pipework needed.

Optimmersion® uses both directional current transformers and voltage sensors to constantly measure the power being generated by Solar PV and also power in use in the home. The clever Optimmersion® system regularly calculates the excess electricity which varies the power to the heating element. The advanced electronics provides a true variable output.


More info

Additional Products

Contact us | Support | Where to buy | Latest news