Should you be specifying home battery solutions?

According to the Solar Trade Association the number of solar panels being installed in the UK has fallen by more than 80%, with a withdrawal of subsidies and hikes in business rates being blamed.

Between January and March, the STA survey noted about 650 rooftop deployments a week – a fall of more than 75% on the long-term average of 2,700 a week since 2010. The association, unsurprisingly, has called on the Government to get behind its Great British Solar Manifesto in a bid to stabilise the industry.

While solar panel installations may have stalled, one of the connected elements of many a solar system - a home battery - may live to fight another day. A heap of tech entrepreneurs, not least Elon Musk, are betting on consumer demand to store power to drive sales of home storage systems.

 Why would householders need a home battery?

• Householders are increasingly looking a self-generation through, say, solar or wind power. Unfortunately a major drawback to these technologies is that they don't provide a constant steady stream of power. Use of a battery system means energy can be stored to fill in the gaps in service when solar or wind doesn't work. Householders can even sell any stored surplus back to the grid.
   
• A battery can serve as a generator / uninterruptible power supply to ensure power is always available, even when the National Grid fails. With the gap between demand and supply set to dip as power stations come to the end of service this may be a compelling case to buy in the years ahead.
   
• A battery system could help reduce power spikes on the grid by flattening peak demand and ensuring that demand spikes (such as turning on air con or multiple households boiling kettles at the same time) can be met.
   
• Energy suppliers are also keen for householders to invest in home batteries. Smart meters (currently being rolled out across the UK in a programme that runs to 2020) open up the possibilities of prices that fluctuate according to time of day or even demand. With a battery system householders could stockpile energy at cheaper rates for use during the day without having to draw this down from the Grid at the time of use.
   
• The Government's move to ban the sale of petrol and diesel cars and vans from 2040 means that more of us will be investing in electric vehicles in the years ahead, dramatically increasing the amount of power individual households require. A battery could be one way of ensuring that household needs are met.

How much energy does a typical household consume?

As you'd expect, it all depends. What are your power demands and how do these vary by daypart? How long do you want to power your house on a battery? Rhett Allain from Wired.com did some calculations on what householders would need and the kind of battery needed to support that a few years back. Tesla estimate a one bedroom household would consume 5kWh a day, a two bedroom household 10kWh, three bedroom household 15kWh per day. Six bedrooms and you're looking at household consumption of 40kWh or more.

Who's working on home battery systems?

It's Tesla's Powerwall 2 that's garnering most media attention. It's a wall-mounted 264-pound lithium-ion device and those cells had been coming from Panasonic but are now created at the firm's Gigafactory in Nevada. One unit will store 13.5kWh but up to ten units can be linked to increase capacity. With a single unit coming in at £5,400 you'll need deep pockets to up your storage.

Elsewhere, LG have partnered with Sunrun to develop its RESU battery (under the LG Chem brand) and can store up to 9.8kWh with prices starting at $4000 USD. 

Automotive manufacturers have natural synergies with this emerging new market. Mercedes has partnered with Vivinit to sell a home battery unit - Mercedes-Benz Energy Storage Home for the first time in the US. It stores 2.5kWh individually, or up to 20kWh across multiple units. The biggest storage option comes in at $13,000 USD including installation.

Closer to home Nissan has announced plans to sell its XStorage Home battery systems manufactured at its Sunderland plant through a partnership with US power firm Eaton. The batteries are about the size of a conventional heating boiler and will cost from £5000. Batteries will be supplied new or reused from cars. These will attract 10 and 5 year warranties respectively.

IKEA have also announced plans to team with Solarcentury, the UK's biggest solar supplier, to offer a system starting at just £3000. UK startup Powervault's product starts at a 'mere' £2,500.

How much money can householders expect to save?

IKEA and Solarcentury say users could save up to £560 per year, in part because the average home with solar sells its surplus energy back to the National Grid at a loss. They estimate the average time to pay off the investment will be around 12 years.

So, the big question: Specify now or wait and see?

With growing demand for power and a constant, stable connection, it's no surprise to see manufacturers rise to the challenge. Indeed, a survey from SmartestEnergy, a renewable power buyer, found that many of the entrepreneurs involved in renewable energy had reacted to government subsidy cuts by moving into the burgeoning battery sector. It counted 20MW of commercial batteries operating in 2016, which it predicted would increase 27-fold by 2020.

There's evidence that costs are starting to decrease as battery technologies become more mature but there's clearly an appetite to create ever-higher capacity batteries to solve the 'range concern' in vehicles and all kinds of development underway to experiment with different battery technologies and £246m pledged to battery research it's clear the technology is competent, useful and even profitable for many, but not mature. For now though it definitely remains one to watch.