Will battery storage affect my feed-in tariff payments?
Posted by Sandra Hayes on 16 August 2016 at 3:45 pm
Q. Will battery storage affect my FiT payments?
A. A recent question from a YouGen reader about the impact of battery storage on Feed-in Tariff (FiT) payments for solar PV got me thinking. My initial reaction was that FiT payments wouldn’t be affected by storage as FiT payments are made for every unit generated –right?
It turns out that the answer isn’t as simple as that. As I found out when I started digging into this, it all depends on the way in which the battery storage system is linked into your solar PV system. Bearing in mind that batteries can only store DC electricity your system could either be:
DC coupled –meaning that the batteries are installed on the same side of your inverter as your solar panels; DC electricity is stored and only converted to AC electricity when it is used, or
- AC coupled – the batteries are stored on the grid side – the electricity has been converted by your inverter to AC electricity and measured by your generation meter before being stored in the battery. A second inverter is required to convert this back to DC electricity again (and back again to AC when you need it).
As you can appreciate the advantage of the DC coupled system is greater efficiency (as energy is lost on each conversion from DC to AC). However, it has the disadvantage of reducing payments through the FiT. Remembering that part of the FiT payment is based on what is recorded by the generation meter, this could happen for two reasons:
If DC electricity is drawn directly off the battery for use before it reaches the generation meter
- Because batteries lose energy in the charge-discharge cycle and this lost energy is not measured by the meter.
The second part of the FiT is the export tariff. Currently this is not likely to be affected if you store the electricity you generate in a battery. This is because the amount you export is usually deemed for domestic systems at 50% of what you generate. Once smart meters are introduced (and every GB home should have one by 2020) this is likely to change so that payments will be made only for what is exported. Storage will reduce your payments but this is likely to be offset by the savings that are made by being able to use electricity your panels have generated rather than paying for imported electricity.
I found a really helpful guide from BRE and RECC on this subject called Batteries and Solar Power: Guidance for domestic and commercial consumers. I recommend reading this guide (see section 4.4) if you want to know more on this subject. The diagrams in it will make everything I’ve said above much clear. It states that you’re more likely to be offered an AC coupled system if you’re looking to add a battery storage system to an existing solar PV system and a DC coupled system if you’re installing a new one.
So how are the commercially available domestic solar PV storage systems currently configured? Telsa say that their Powerwall is a DC-coupled battery which requires a compatible inverter. Retrofit seems possible but pricey because a new inverter is likely to be needed as well as the battery pack. The Powervault is an AC-coupled system, so installing one won’t affect your existing FiT payments. In theory at least it should be a cheaper option for retrofit as is no need to change the existing inverter. In simple terms the AC option would appear to lend itself to retrofit whereas DC option is likely to better suit a new build project.
If you have any direct experience of battery storage why not post your comment here? I’m sure there’s a lot more that can be said on this subject!
More information about Energy Storage on YouGen
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