I’m a bit of a hippy. It’s no secret. I juggle, I have multiple pairs of harem trousers, and am currently sporting an undercut. I’m also a bit of a capitalist though, so when I installed solar panels on my house in 2014 it ticked the boxes of reducing my carbon footprint (over the lifetime of the panels, there is obviously an environmental cost in the production of the panels just as with my electric car) and being a sound investment.
The cost of battery storage solutions has come down since my original install and with the launch of the Tesla Powerwall 2 I figured I had better revisit the situation and see what was up. I have a 1.96kW PV install, and over a year I generate on average 5.4kWh a day, of which I export 4.1kWh (though the feed-in-tariff assumes I only export 50% I actually export around 76%). I obviously also have to import electricity on those occasions when the sun is not hitting the panels hard enough (so, at night), which I currently do from Ecotricity (a bit more costly, but they generate from renewables themselves and it gives me access to their rapid chargers for my car).
So I fired off a couple of enquiry emails to local installers of battery storage systems and received responses the same day (good customer service there). The second company just pointed me at their twitter and facebook pages and didn’t give me any idea of an installation cost (which is what I had enquired about, points lost there), but the first company Ecocetera sent me back a considered reply (within a couple of hours) specific to my install. They included a summary of the different battery storage systems available in terms of both capacity and cost per kWh over the expected lifetime of the battery. They also included cost estimates including labour and delivery (what I had asked for).
They also prompted me to think about how much spare capacity I had to charge a battery, on how many days per year. All of the battery storage solutions assume the ability to charge on 250 days of the year, so I downloaded the numbers from my install and started crunching. For my specific install I probably wouldn’t be able to keep a larger battery like the Powerwall sufficiently charged up (which isn’t good for the battery), so I would be a looking at a smaller capacity battery. Unfortunately the smaller the battery, the higher the cost per kWh (there are a lot of additional gubbins that go along with the battery to manage it, so it’s not just the cost of the physical battery that goes into the overall cost).
All of this number crunching led me to conclude that given there is an environmental cost in the creation of any battery storage system, it actually makes both environmental and financial sense not to add battery storage to my existing PV system. Instead I will keep buying in electricity from renewable sources, keep trying to use as much of my excess solar during the day (luckily I am in a position to run high-drain items such as the washing machine and dishwasher, and charge my car then), and keep investing in green energy projects locally. It also means I don’t have to worry about where to put a physical battery, as well as saving me some money to put towards my Tesla Model 3.