Can my home battery power my house in a powercut?

This is a question we get asked a lot and here we delve into whether or not this is possible.

Most Solar Panel systems are designed with storage in mind, however, a common question we get asked here at Renew-Able Solutions is will my Solar PV system still operate during a power cut?

If backup functionality is essential to your home solar panel system, it is time we introduce you to EPS functionality. Remember you can get in touch with our green team and we’ll design a bespoke solution to match your energy requirements for FREE.

WHAT IS EPS MODE?

With the price of energy on the rise, and more energy in demand, the UK Government believes 6 million homes could face winter power cuts due to energy shortages and if Russia decide to cut off more supplies to the EU. Now with Israel at war with Palestine and unrest in the Middle East, Energy security has never been so stretched. So now more than ever may be the right time to consider adding an EPS to your Solar panel installation.

EPS or Emergency Power supply refers to a Solar PV System’s ability to automatically or manually change over to powering your essential circuits from your battery storage system, in the case of a power cut. The next generation of Hybrid solar inverters are designed to provide EPS, as a way to provide customers with peace of mind during power failure.

DO YOU REALLY NEED BATTERY BACKUP?

When considering installing EPS to your Solar Panel system ask yourself how often will you be using this feature, and whether or not backup storage is essential to your energy needs.

• Do you live in a rural remote area, prone to regular power cuts, for say 1 or 2 power cuts a month?
• Do these power cuts last a short period of time?
• Are you working from home, using servers, mining bitcoin, or using other devices that require continuous power supply such as medical equipment?
• Is your storage capacity large enough to keep reserved power? Remember EPS is limited by the capacity of your battery storage system, and reliant on how full your battery storage system is at the point of grid failure.

THE DIFFERENT LEVELS OF EPS FOR SOLAR

At Renew-Able Solutions we have options for both automated and manual change over Emergency power supply as well as full grid solutions. EPS is an optional extra that can be added to our Solar PV Packages for home and business owners looking to add security.

LEVEL 1: AUTOMATIC SOCKETS

A double 13A socket can be wired to your solar battery system as an EPS outlet. This is a relatively low-cost addition to any solar PV system, yet within just a couple of seconds, it allows the inverter to automatically disconnect from the grid to your socket in the event of a power cut. This is useful for powering small loads, such as charging a mobile phone or a light source. In this case, the socket is just an outlet for what the inverter can do, and will discharge energy at 3kW or 5kW depending on your battery and inverter rating.

LEVEL 2: AUTOMATIC CIRCUITS

With the addition of an extra consumer unit and some wiring the battery inverter can be used to operate one or more circuits, typically lighting and perhaps also the fridge. Again in a power cut after a short delay, these circuits will become automatically powered by the battery system.

Due to power limits on the EPS output, this approach cannot be used to power the whole house as it is limited by the amount of power it can draw.

LEVEL 3: MANUAL WHOLE HOUSE BACKUP

In the event of a power cut, a homeowner can manually turn off all high power loads, and engage a full house switch over where your home demand is now supplied directly from your battery. This is done by rerouting the incoming grid connection and the house main consumer unit, to go through the battery system instead. 

This type of external manual changeover switch is compatible with current SolaX systems. Whilst it may sound like an inconvenient process, it does encourage the owner to turn off unnecessary heavy loads, to conserve your battery capacity for essential use only.

LEVEL 4: AUTOMATIC WHOLE HOUSE BACKUP

If you are looking to power your entire home, with or without a grid connection, an off-grid Victron energy inverter is your best solution. These types of solar PV systems are capable of managing high loads and automatically swapping over to battery energy in an event of a power cut. This changeover is seamless, however, requires a large battery to facilitate the home’s demand which can be costly.

LEVEL 5: AUTOMATIC WHOLE HOUSE BACKUP WITH OFF-GRID CAPABILITIES

Whilst all solar inverters need power to operate, it is possible to design a system in which the battery inverter provides power to the solar inverter so that even when there is no longer a grid connection, the entire house is isolated by the battery inverter.

Unlike the other solutions which are restricted by your battery capacity and storage at the point of the grid failure, in this type of solar PV system, as long as there is sunshine your system will be able to power your home. Essentially providing full off-grid capabilities. An example of such a system would be a Victron Energy system or Tesla Powerwall system. 

HOW DOES THE EPS (EMERGENCY POWER SUPPLY) WORK?

EPS functionality gives a home or business owner access to the energy stored in the battery in the event of grid failure. These features can be used to continue to power the essential circuits in your home or even the entire home in the instance of a power cut. 

90% of the hybrid solar inverters on the current market will come with the hardware to support EPS compatibility, 70% of these inverters will require you to install external components, in order to access this functionality. 

Most of the time in EPS mode you can only use the energy stored in your solar batteries. It is only with certain leading brands, such as GivEnergy, Tesla and SolarEdge (firmware pending), that you can also generate solar energy during a power cut. It is also these leading brands that offer an all-in-one solution. 

The Tesla Powerwall is an example of an integrated battery system that can store solar energy, as well as provide backup protection. When installing the Tesla Powerwall, the switch to backup mode in the case of a power cut occurs seamlessly. 

HOW IS EPS INSTALLED?

Despite popular belief, many solar batteries will not provide you with a backup supply straight out of the box. In order to add EPS functionality to your solar panel system, if your inverter doesn’t have the hardware, you need to install an automatic contactor or manual changeover switch to your hybrid inverter. Also depending on the earthing arrangement of the property and how the grid is disconnected, you will have to install a new external earth, along with a fused down distribution board to link out the circuits. We will usually install a 20A or 43A contractor depending on the size of the discharge of the inverter. It is then time to calculate the size of the circuits that you would like to be powered, (we recommend 43A) which then have to be connected to the backup distribution board. This is a time-consuming addition to any solar panel installation and should be planned for ahead of installation. 

IS AN EPS SOLAR SYSTEM RIGHT FOR ME?

EPS or Emergency Power supply can be an expensive addition to any solar panel solution, however worthwhile under the right circumstances.

If you are a UK home or business owner interested in discussing solar panel battery backup, contact our award-winning green team today on 0131 210 0405 for expert advice.