Tesla has confirmed it will unveil a revolutionary power pack for the home next week. The California firm said it will announce a 'home battery' and a 'very large utility scale battery' in a letter sent to investors. While products such as this already exist, founder Elon Musk thinks they 'suck', according to Tesla's investor relations director, Jeff Evanson. Scroll down for video . The California firm said it will announce a 'home battery' and a 'very large utility scale battery' in a letter sent to investors. The company already offers battery packs (pictured) for its SolarCity project, but it is unclear whether the latest product will build on this design . There are a number of home battery packs on the market. Most work by powering up overnight when electricity rates are cheaper. Users can then switch them on during the day to use the home during the day. They can be used as back up power in the case of an emergency, or be used to hold power from renewable energy sources. Home battery packs could disrupt the utility market. In 2013, the Edison Electric Institute, the trade group for investor-owned electric companies, issued a report warning about disruption. 'One can imagine a day when battery storage technology or micro turbines could allow customers to be electric grid independent,' the report said . Musk announced the event last month in a cryptic tweet that said there will be a launch of a 'major' new line of products that is 'not a car'. The event will be held at Tesla's Hawthorne, California, Design Studio on April 30 at 8pm. PT. '[At the event] we will explain the advantages of our solutions and why past battery options were not compelling,' the company said. Home batteries power up overnight when electricity rates are cheaper. Users can then switch them on during the day to use the home during the day. In February, Musk said their version of a home battery would be ready for a public debut within months and that it should start going into production by the summer. It is likely to build on the power packs used in Tesla's range of electric cars such as the Model S. 'We are going to unveil the Tesla home battery, the consumer battery that would be for use in people's houses or businesses fairly soon,' Mr Musk told analysts earlier this year. 'We have the design done, and it should start going into production in about six months or so.' He didn't reveal what a home battery would be used for, but it could act as a generator during a power cut, for example. While products such as these already exist, founder Elon Musk (left) thinks they 'suck', according to Tesla's investor relations director, Jeff Evanson. On the right is an image of a Tesla residential battery being installed . Tesla's billionaire founder last month fuelled speculation by saying it 'not a car' and added the product will be revealed at the company's California, Design Studio on April 30 at 8 p.m. PT . But at a conference last year, Tesla's Stationary Energy Storage Director Arch Padmanabhan revealed some of Tesla's initial plans. The Mirai features the Toyota Fuel Cell System, which combines fuel cell technology with hybrid technology. The firm said it can serve as a 'high capacity power supply during emergencies'. The Mirai converts the DC power from the CHAdeMO power socket in the boot to AC power, using an attachment. Toyota calls it a vehicle-to-home system. Tesla's home battery could work in a similar way, or be a standalone battery. This included a 400 kWh commercial/utility battery for large buildings and a 10 kilo-Watt hour residential battery. Rival car manufacturer Toyota already uses a hydrogen fuel cell in its Mirai car that can be removed and used to power a home. According to the Japanese car maker, the battery can supply electric power to an average home for a week. Last year, Tesla Motors unveiled plans for a 'Gigafactory' designed to help the firm ramp up production of batteries for its electric cars, and now homes. Tesla said the factory will cut current battery production costs by up to 30 per cent, and will be powered predominantly by renewable energy sources, such as wind and solar. Elsewhere, Mr Musk is already the chairman of SolarCity - a company that offers solar power systems for homes - and Tesla's home battery could be an extension of this. These batteries 3ft tall (0.9 metres), and can be controlled remotely using a smartphone app. Tesla would not comment on whether the new batteries will work in the same way. Home battery packs could disrupt the utility market. In 2013, the Edison Electric Institute, the trade group for investor-owned electric companies, issued a report warning about disruption. 'One can imagine a day when battery storage technology or micro turbines could allow customers to be electric grid independent,' the report said .
Event will be held at Tesla's California Studio on April 30 at 8pm PT . Battery is likely to build on the packs used in Tesla’s electric cars . While similar products already exist, Elon Musk has said they 'suck' Toyota already uses a fuel cell in its Mirai car that can power a home .