Hot water cylinder vs Thermino – which hot water system is right for you?

Is it time to upgrade your hot water system? Whether you’re looking for a hot water cylinder replacement, or you’re changing your heating system and need a compatible hot water solution, there are many options on the market. Which one is right for you will depend on your priorities – there are a number of factors to weigh up, including space, efficiency and maintenance requirements.

Start with your heating system

How you heat your home will have an effect on which hot water system you need. 80% of homes in the UK have a gas combi boiler which provides both space heating and hot water, meaning you don’t usually need a hot water cylinder. However, gas boilers are on the way out, with the UK government looking to phase out the installation of new gas boilers in most homes from 2035. There are also 1 million homes in England, Scotland and Wales which aren’t connected to the gas grid and must use another fuel for heating.

If you don’t have a gas combi boiler, you may heat your home using electricity, renewable energy, oil or LPG. Oil or LPG is most common in Northern Ireland, where oil is stored in a tank and used to power a boiler. Oil isn’t a sustainable option and can be expensive as the price is subject to fluctuation.

Another option is electric heating. As we move away from fossil fuels electric heating is likely to become the dominant option, but currently electricity is more expensive than gas. This means electric heating is more viable when paired with renewable technology such as solar panels. Traditional electric heating systems are more common in flats and are typically made up of separate electric heaters in each room, rather than a central system. An example is storage heaters, which charge overnight on a cheaper electricity tariff and release heat during the day.

Renewable heating systems are often powered by electricity but are more efficient than traditional electric heaters. For example, heat pumps capture heat from the outside, either from the air or the ground, and use this to heat your home. Although they’re powered by electricity, the amount of heat they produce is more than the amount of electricity they use. Heat pump uptake is key to moving away from gas boilers, with the Climate Change Committee predicting heat pumps will be needed in up to 80% of UK homes by 2050 to meet net zero targets.

When moving away from a combi boiler to any of these alternative forms of heating, a separate hot water system is needed. This often takes the form of either a vented or unvented hot water cylinder. These take up a lot of space in the home and can suffer from heat losses which reduce the efficiency of the system when compared to a combi boiler.

Alternatives do exist, such as Thermino heat batteries which are compact, efficient, and work with a range of heat sources, from heat pumps and solar PV to boilers and grid electricity. Thermino batteries can also be used as part of a mix and match approach for households looking to separate their heating and hot water and go for a more sustainable hot water system now, with a view to swapping their gas boiler for a heat pump in the future.

Types of hot water cylinders

In England alone, nearly 9 million homes use a hot water cylinder. This includes indirect hot water cylinders which are used with an external boiler, usually powered by gas or oil, which heats the water by heating a coil inside the cylinder. Direct hot water cylinders use an immersion heater to heat the water and are powered by electricity, so can be used in homes without a boiler.

A Thermino heat battery can replace a direct or indirect hot water cylinder, with one model powered solely by electricity from the grid or a solar system, and another which is powered by a boiler or heat pump and can also be linked to solar PV, with grid electricity as a backup.

Another key difference is between vented and unvented hot water systems. Vented systems are usually made up of a copper cylinder in an airing cupboard, an expansion tank in the attic, and a cold water tank. Unvented cylinders are directly connected to the mains so don’t need a hot water tank in the attic, just a cylinder in an airing cupboard.

Advantages and disadvantages of hot water cylinders

There are pros and cons to both vented and unvented hot water cylinders. Vented systems are usually cheaper to install and require low maintenance, but the cold water storage tank is large and open at the top which can risk contamination. The pressure of a vented system relies on gravity, which means pressure is often lower at upstairs outlets and an additional pump may be needed to boost the pressure.

Unvented systems are sealed, so have less risk of contamination, and operate at mains pressure. This can give better flow rates and means the cylinder can be placed anywhere in the home, as it doesn’t rely on gravity to create the pressure. However, these systems are more expensive to install as they require G3 certification, and need regular maintenance to comply with safety regulations. Although unvented systems take up less space than a vented system as you only need one cylinder, this can still be a challenge in space-constrained homes.

The difference between a hot water cylinder and a thermal battery

Thermino heat batteries are an ideal hot water cylinder replacement. The main difference between a thermal battery and a hot water cylinder is that heat is stored in a phase change material, rather than in water. Sunamp’s Plentigrade phase change material is much more energy-dense than water, meaning a Thermino battery can be four times smaller than the equivalent hot water cylinder. This solves the issue of finding space for a hot water cylinder, which is helpful in the move away from gas boilers, as it means a heat pump can be fitted in homes which don’t have room for a hot water cylinder.

The fact that heat is stored in a phase change material, rather than water, overcomes another issue with hot water cylinders. Cylinders can be prone to limescale buildup and there is a risk of Legionella. Thermal batteries don’t store a large volume of water, which helps prevent this risk. The anode within a hot water cylinder can also be prone to corrosion as the immersion is in direct contact with water, whereas the heating element within a Thermino is embedded in the phase change material.

Another disadvantage of hot water cylinders is the high heat losses. The vacuum insulation panel in a Thermino leads to typical heat losses of just 0.77kWh over 24 hours, compared to 1.42kWh for a hot water cylinder. Again, this is a bonus when switching from a combi boiler to a heat pump – if using a cylinder, the heat losses can bring down the overall efficiency of the new system, whereas a thermal battery stops this energy being wasted.

Thermino batteries can reduce energy consumption due to the lower heat losses and don’t require any annual maintenance, which can reduce ongoing costs. Hot water cylinders need an annual service to prevent common problems, usually costing between £60 and £80. Unvented cylinders must be installed and maintained by someone with G3 certification, unlike Thermino batteries which just need to be installed by a competent person.

With 25,000 systems installed worldwide, choose a compact and super-efficient Thermino over a hot water cylinder for ultra-low heat losses and on-demand hot water at mains pressure. If you’re ready to get started, find a stockist or installer here.

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