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Mixergy tank is dynamic tariff ready – are you?

By David White Feb 26, 2021
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Mixergy’s aim is to enable the mass decarbonisation of our energy network through the provision of affordable, flexible and smart hot water cylinders, building Europe’s largest virtual battery in the process. We help our customers lower their carbon impact locally in 3 ways:

  1. By only heating what is needed, the cylinder’s standing heat losses are lowered and less energy is wasted in the generation of the hot water.
  2. We allow customers to connect to and utilise multiple local carbon energy sources throughout the working life of the Mixergy tank ie. Connecting to solar PV and heat pumps.
  3. We use smart machine learning algorithms to deliver the household’s hot water at the lowest possible cost and carbon impact.

One way of lowering carbon intensity at a macro scale is to ensure that low carbon energy generated on our National Grid is used by households. At the moment this doesn’t happen on a wide scale as the vast majority of households are on fixed rate tariffs and there is no incentive to use electricity at off-peak times or during instances when there are surpluses of renewables and the low carbon energy mix associated with UK generation is at its highest. The energy industries solution to this is to offer dynamic or ‘time of use’ tariffs. These tariffs pass on wholesale electricity pricing to customers. So what does that mean?

The wholesale market broadly operates in this fashion: National Grid must ensure that supply and demand is kept in balance at all times, to help facilitate this, they operate a market for electricity which sets a price for any imbalance every 30 minutes. During peak hours when more demand is expected the price of this electricity is higher. During off-peak times there is more solar and wind energy being contributed to the overall grid energy mix and as a result the carbon intensity and price of this power is lower.

One of the most popular time of use tariffs on the market is the Octopus Agile tariff. This tariff provides customers with 24hours worth of half hourly pricing data every day at 4pm, allowing customers to plan when to use their energy, taking advantage of the lowest price periods every day.  The prices can drop much lower than the price of gas (usually at <3p/kWh) and can even go negative meaning you get paid to use energy! But without having smart devices that can automatically respond to these changing prices, time of use tariffs can be cumbersome to live with…

The above graphic is from the Octopus website showing the price variation in comparison the ‘Big Six’ standard tariffs. You can see that cheapest electricity rates are between 02:30-05:00 and most expensive rates between 15:30-19:00.

Our smart machine learning algorithms have now been developed to allow customers to automatically take advantage of these variable price points, building a new daily schedule ensuring you have enough hot water to meet your needs, whilst ensuring it is delivered at the lowest possible cost.

When Mixergy’s agile interface is enabled the tank will use the lowest cost half-hourly windows to delivery the daily hot water needs. Below is an example of a Mixergy customers single days hot water heating profile responding to the Agile price point:

The Mixergy tank will even choose between gas and electric as its primary energy source if your cylinder is also connected to a boiler:

Here is some feedback from some of our Agile integrated customers:

“I did think the Agile functionality was remarkably clever. It didn’t just choose blocks, it’s picked out the cheapest periods to maximise the savings, so it would switch on, off and on again as appropriate to get the best half hours. So it worked really well.” Antony Walker,Agile integrated customer
“My experience of the Mixergy Tank with Agile Integration has been perfect for us. After setting the gas price per Kwh in the Mixergy app and the Automatic Schedule Control to Standard (or Economy) the system automatically uses electric heating in the half hour slots when the Agile electricity price is below our gas price. 

What is particularly good is that the system uses the best half hour slots it can to heat as much water as possible. For example, one night we had Agile rates plunge below -4.41p/kWh for several slots and the system used those even though there were earlier slots of -1.10p.  The Agile Integration assumes that it should heat as much as possible and will go to 100% if it can.  This may not suit everyone, but as the tank retains the hot water over a long period of time it works for us.

Whilst initially I did check the graphs each day as I was curious as to what it would do, after a few days I knew I could leave it to do its work and wake up to a 90-100% tank of hot water when rates were low.” Peter Danson,Agile integrated customer

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