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Optismart® Hot Water
The all-in-one smart solution to maximise auto-consumption

What is Optismart® Hot Water?

It provides free hot water by proportionally diverting surplus renewable electricity to the immersion heater. It starts heating water from 50W, and it gets its data using current transformers. The solution is fully automatic and can be added to any solar power installation and immersion heating system.

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.

What people are saying about Optismart® Hot Water

“We were quite impressed with the system.The installation was straightforward as the instructions were easy to follow. We noticed this version of the Optimmersion® system was a bit more expensive but it does so much more!”

Hudson Electrical and Plumbing Company

Product information

Optismart® Hot Water you get a cost effective solution to share the benefits of Wattson Solar Plus and Optimmersion all in one!

The Wattson display can also show you any where in the house how much surplus is being diverted to the immersion tank.

With Optismart® Hot Water you can add an Optiplug or two to really start making the best use of your generation with other appliances.

Can save 20% on yearly electricity bill with Wattson & Holmes showing usage costs

Optismart® Hot Water OSHW-NLEN-UK

Optismart Hot Water comprises an Optimmersion® and a Wattson Solar Plus display in one cost effective solution that is cheaper and quicker to install than buying them separately. The dedicated Wattson display included has an additional mode showing diverted power.

The transmitter in the Optimmersion can also send data to the Wattson Anywhere portal via the Optismart Gateway and can control Optiplugs to make best use of generation with other appliances.

Wattson Solar Plus is an energy monitor that makes it very easy for everyone to see when they are generating more power than they are using by glowing green and shows how much more power they could be using for free in big bright numbers. When they are importing a small amount of power from the grid it glows blue and gets redder and redder the more they are buying in. It also shows them the cost of the power they buy so they can make better informed decisions about usage to bring their bills down.

Why choose Optismart® Hot Water:

Optismart┬« Hot Water has replaced the Optismart┬« Hot Water OSHW-WIEN-UK in the new-look Optimmersion range. Optismart® Hot Water has two main components, the power throttle and the controller.

The controller needs to be accessible as it has an operable switch and the colour display. Optismart® Hot Water is a fully flexible system as not only does it have full control functionality with the controller unit such as automatic water heating management, timer and boost settings, but the wireless power throttle can be placed anywhere along the spur to the immersion.

Optismart® Hot Water has a Wattson transmitter integrated so the Wattson display will show you the amount of energy being diverted to the tank in realtime. Adding an additional Optiplug will alsogive your property a complete solution to make the best use of your spare generated electricity.


Additional products

* Holmes. Download the free Wattson Solar Plus software to start recording and storing your usage and generation data.

Where to buy

Benefit from the renewables reduced VAT rate of just 5% when Optimmersion® is bought & installed by a qualified installer.


Optimmersion® is available from your usual Wattson supplier.

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