Frequently Asked Questions

How the ZEB works

As the ZEB is a heat battery, it will work slightly differently to your existing boiler.

Just like your phone battery charges up using electricity and draws down on this stored energy as needed, the ZEB also uses electricity to charge up, storing energy as heat that can be used on demand when you want to heat your home. The ZEB intelligently stores the right amount of heat based on your needs, the weather and your tariff, mostly charging up at off-peak times e.g at night to minimise electricity costs and topping up during the day if needed. How long a full charge lasts depends on the property size, heating usage and the weather.

Can a ZEB heat my home?

The ZEB works with most ‘wet’ central heating systems i.e. homes with pipes and radiators. The ideal home for the ZEB is a flat, bungalow, semi-detached or detached home that has up to 16,000kWh annual energy usage and a heat loss of under 6kW. You can find your energy usage on the bill from your energy supplier. The ZEB is an easy switch from a gas, oil or electric boiler, taking only 1-2 days to install, making it a great option if you’re looking for a green home heating solution but you’re not able to install a heat pump.

What is the storage medium made of?

Proprietary mix of high-density, inert, non-toxic and low impact materials

How much energy does it store?

40kWh of usable thermal energy

How much power can it output?

15kW maximum

What temperature water can it supply?

Just like a fossil fuel boiler the ZEB can supply any water temperature from 35 – 80°C in a suitably sized home as set out here. Your current boiler won’t be higher than this so you won’t notice a difference.

How efficient is the ZEB?

Installation within the heated envelope of the home rates a ZEB at 100% efficient at converting fuel into heat, as the ZEB converts 100% of its electricity consumption into heat (classified as 100% efficient for EPC purposes); installation in garages or unheated spaces is not optimal and may result in increased standing losses and reduced capacity.

To improve overall system performance, we advise our customers to use immersion heaters with a timer for hot water heating, rather than using the ZEB for water heating, particularly in the summer months.

It’s worth noting that when the ZEB is charging, it becomes a little bit warm itself – the surface temperature is cooler than a radiator but there are small heat losses, which will heat the area where the ZEB is located.

How long does it take to charge?

4-5 hours from empty. It can deliver heating after half an hour (from cold).

What are the dimensions of the ZEB?

98cm (height) x 60cm (width) x 66cm (depth) – but it needs clearance of 7.5cm above and 5cm on all sides. This can be reduced in certain situations, your tepeoPRO will be able to advise.

How heavy is it?

375kg.

How does it work?

The ZEB is an innovative low carbon alternative to a fossil fuel boiler. Using a Smart Charging algorithm, the ZEB ‘charges up’ with off-peak electricity to keep costs low and stores this as heat inside its core, supplying your central heating system and hot water cylinder on demand.

How long will it last?

We’ve designed the core of the ZEB so it doesn’t degrade over time, in fact there’s a good chance it will outlast the home it’s installed in! However, the ZEB still needs to be maintained, like all boilers, and so we provide two options to support this – a standalone annual ZEB Health Check or our tepeo Care Plan here.

How often should the ZEB need servicing?

The ZEB should have an annual Health Check (typically costing £149), which involves a tepeo trusted engineer checking the water quality in your heating system, clearing filters, visually inspecting parts for wear and tear, including cleaning where necessary, checking for leaks, carrying out an electrical safety test and generally ensuring the ZEB is running smoothly.

Unlike an annual service for a traditional heating system, a ZEB Health Check from tepeo includes all of the parts that may be needed – without any hidden costs.

For comparison an annual heat pump service typically costs around £200-£250 and a standard boiler service costs up to £120-£130.
You’ll automatically receive a yearly reminder of when your Health Check is due once your ZEB is installed.

Where does tepeo deliver to?

To see if we cover your area for delivery, please click here.

Do I need to register my ZEB?

Your ZEB will be automatically registered during installation so there’s no need for you to do anything. The 10-year guarantee will be activated from installation.

Terms and conditions apply.

How do I report security concerns about the ZEB or tepeo App?

Please contact the customer service team if you have concerns about security of the ZEB or tepeo App (see the Contact Us page for details).

How long will tepeo provide security updates for the ZEB (under the Product Security and Telecommunications Infrastructure [PSTI] regulations)?

We will provide security updates for a minimum of 5 years from the date of purchase.

How is it different than a storage heater?

The ZEB uses electricity and stores it as energy, much like a storage heater. However unlike a storage heater, the ZEB has smart capabilities where it can predict how much to store based on the weather, your tariff and your predicted usage. It also allows you to store energy at the cheapest and greenest times to be used on demand when you need it. As such, it works as a direct replacement for your existing boiler.

How is it different from a gas/oil/lpg boiler?

The ZEB is a direct replacement for your existing boiler, but it doesn’t use fossil fuels to heat your home. Instead it uses electricity, which is a cleaner alternative and can support the UKs move to Net Zero.

How is it different from an electric boiler?

The ZEB ‘charges up’ with electricity from the grid at times when it’s cheapest and greenest, storing it as heat to be used on demand when you need it. Electric boilers on the other hand take electricity from the grid whenever you need heat, which makes them significantly more expensive to run, as it’s using peak electricity, which is more expensive and has a higher carbon intensity i.e. it’s dirtier.

How much does the ZEB cost?

A ZEB costs £6,000 to purchase, which includes VAT and delivery. Currently, the ZEB isn’t zero-rated for VAT purposes (20% VAT applies) and doesn’t receive any subsidies (but we’re working on it).

Installation costs vary and depend on your home, heating system requirements and local installer rates – we can put you in touch with a tepeoPRO installer in your area to get a quote specific to your home.

We can also provide a tepeo Care Plan subscription to help maintain your 10-year guarantee. Find out more here.

What tariff do you recommend?

We recommend a time-of-use tariff, with 1 or more off-peak periods. Octopus, OVO, EDF, Scottish Power and others offer these, often marketed for EV drivers. Alternatively dynamic tariffs will also make full use of the ZEB’s flexible storage and let you take advantage of surplus renewable generation and (potentially) negative pricing. Which one will be the cheapest for you will depend on your other consumption needs.

You should also explore what the best boiler settings are for you to save money. We have resources available for helping you optimise your habits and heating system to make the most of your ZEB.

Does it work with Octopus Agile?

Octopus Agile is a fully dynamic tariff which has a different price for every half hour of the day. The ZEB can automatically optimise charging for this tariff.

Does it qualify for the Boiler Upgrade Scheme or other grant funding?

As this is a new technology, it does not yet qualify for any grant or subsidy support. We are working to change this in future and to get tepeo’s ZEB recognised by government incentive schemes to reduce carbon emissions.

Will my heating costs go up?

This depends on your tariff and heating demand. You can check out our new boiler savings calculator which will help you figure out your potential cost savings and carbon savings.

Can it go in my loft?

Unfortunately not, the weight of the ZEB makes lifting it into a loft impractical.

Can it go in my basement?

Yes, if your basement has a steel or concrete staircase which isn’t too narrow.

Can the ZEB go outside?

No – the ZEB needs to be in a weatherproof, insulated environment, so somewhere inside the home.

Can the ZEB go in my garage?

Yes – however the ZEB does lose some heat to the environment. If installed outside of the ‘heating envelope’ of the home, heat losses don’t contribute to the heating of the home (instead heating your garage). The loss rate of a ZEB is 280W (at 50% state of charge), however this is very dependent on how you use your heating and what tariff you are on.

Does it need an internet connection?

It needs an internet connection, although the ZEB is resilient to temporary connection outages. This can either be provided over WiFi or Ethernet.

I don’t have Wi-Fi where I want to install the ZEB…

The ZEB requires an internet connection to work, so you can use ethernet as an alternative to Wi-Fi.

Will I notice any difference in my heating/hot water?

No – the ZEB behaves exactly as your conventional boiler does.

Can my plumber/electrician install it?

All installations must be installed and commissioned by tepeo or a competent and qualified installer who is registered with tepeo. All installations must also be in accordance with the manufacturer’s instructions, applicable legal requirements, regulations and industry standards. They can find out how to become registered here.

Do I need to change anything in my home (retrofit) to have a ZEB?

You don’t need to make any changes to your home to have a ZEB, it will work with your existing setup and heating system, although you will need a hot water tank if you don’t already have one. The ZEB can work in homes with an annual energy usage of up to 16,000kWh and a heat loss of under 6kW – we’ll check whether a ZEB is the right fit for your home during a home survey.

What electrical connections are required?

• Power via double pole isolator, directly from the consumer unit (50A breaker/RCD protection, 10mm2 min cable size).
• Heating system power output 3A fused spur (non switched) to wiring centre. And/or direct to external pump for ZEB-controlled pump overrun.
• Thermostat heat demand signal (230v or Volt Free).

Can it replace my existing gas/oil/lpg/electric boiler?

Yes, the ZEB is a direct replacement for a gas/oil/lpg/electric boiler.

Can I replace my storage heaters on Economy7 tariff?

The ZEB needs a ‘wet’ central heating system i.e. your home has radiators or underfloor heating to be able to deliver heat to your home. Typically homes with storage heaters don’t have a ‘wet’ central heating system, so these will require changes to be made to your home. If storage heaters were installed alongside or without removing the wet central heating system, then the ZEB can be easily installed.

I have a dry heating system – will the ZEB work for me?

No, the ZEB is only suitable for ‘wet’ central heating systems, as it needs pipes and radiators to deliver heat to your home.

Can it replace my combi boiler?

You will need to combine the ZEB with a hot water solution, as the ZEB is a heat only boiler. There are many options to choose from like hot water cylinders, smart cylinders and PCM heat batteries. Your tepeoPRO will be able to recommend the right solution for you or you can learn more here.

What plumbing connections are required?

Central Heating – Flow/Return 22mm copper – solder or compression/press fit.

Anything else required?

• Isolation valves – on both flow and return so the ZEB can quickly be isolated from the heating system for maintenance without draining the system. Take note of PRV requirements – refer to the installation manual on our Documentation page here.
• Automatic bypass valve – to ensure minimum flow through the ZEB even when the heating system TRV valves have closed.
• Pressure relief valve – to ensure the system pressure stays within limits.
• Magnetic System Filter – to help ensure the ZEB heat exchanger stays free from contamination (which would reduce performance).

Do I need a smart meter?

In order to access lower-cost electricity tariffs, you will likely need a smart meter and a smart tariff from your energy supplier.

However, the ZEB is able to optimise charging so it minimises your carbon footprint without a smart meter.

Can ZEB draw electricity at the same time as my EV charger?

Yes, a typical charger will draw 30A, the ZEB 40A, so together 70A – less than the typical 100A household limit, depending on other loads in the house at the time.

My heating demand is high – could I get two units and charge both overnight?

This is theoretically possible, as each ZEB draws 40A so in combination they would draw 80A vs. a household limit of 100A.

We hope to fully support parallel running soon.

What happens in a power cut?

Just as with a conventional boiler, the circulation pump will not work if there is no power supply, so heat will not be provided. The stored heat will remain in the core for several days but will slowly be lost.

What happens if I demand heat at a faster rate than it can be replaced in the ZEB?

The ZEB has a class-leading 40kWh of high density storage so that it can independently charge (at low-cost off-peak times) and discharge (when heat is demanded). However, during periods of high heat demand, the ZEB is able to simultaneously charge and discharge (requires a minimum SoC). The ZEB discharges in the range 0-15kW and charges at up to 9kW – stored heat in the ZEB will deplete faster than it can be replaced if the discharge rate exceeds charge rate.

I have solar PV, can I use the excess to charge the ZEB?

This feature is currently under development.

How does Smart Charging Work?

Our Smart Charging algorithm charges the ZEB at the cheapest and greenest times of the day, ready for when you need it.

This factors in:

• Local weather.
• How much heat your home uses.
• The carbon intensity of electricity and the pricing of your energy tariff.

Like many smart electric boilers, the ZEB works best with “time of use” or “flexible” tariffs where the price you pay for electricity changes throughout the day.

Can I control my ZEB remotely?

Yes you can! Take control of your ZEB from anywhere with the tepeo App. Get insights into the energy and carbon from your ZEB. The tepeo App is available on iOS and Android.

How much CO2 will I save with a low carbon heating boiler?

An independent climate impact report has found that if a home with a heating demand of 12,000kWh/year switched to a ZEB instead of a gas boiler they would save up to 2 tonnes CO2 equivalent per year by 2030.