So, I had a client request the CO2 savings figures for systems with PV vs. the same systems with battery storage included. 

Of course, I had assumed that the systems with batteries included would have greater CO2 saving figures (or "CO2 emissions avoided" figures).

However, the CO2 emissions avoided figure is slightly lower for the systems with battery. An example (not actual figures but there about!):

* 170kWp Solar PV system with no battery: 150,000kWh/year production, 60,000kg/yr CO2 emissions avoided

* 170kWp Solar PV system with battery storage: 150,000kWh/year production, X amount stored in battery, 58,000kg/yr CO2 emissions avoided

How can this be? The only things I can think of are:

> Perhaps it is not including the battery storage figures, and so the CO2 avoided stays roughly similar. However, I think this is unlikely as each time I did this on different systems, the CO2 avoided seemed to decrease by roughly the same amount each time I added batteries, and it never increased.

> Perhaps it takes into consideration the CO2 in the production of the battery?! This also seems unlikely. 

I just don't want to say to a client: "You will save more CO2 if you don't have a battery installed", as then the client is likely to not have the battery installed, when in fact this will help their energy bills etc far more than just the Solar PV. 

 

Thank you

Hi GeorgeRymer96,

the avoided CO2 emissions are calculated using the average CO2 emissions applied to one kilowatt hour of drawn grid electricity.

Without knowing your project files I assume the battery storage is configured with full and equalization charging strategies. Because it is maintenance charging, it does not matter whether it is photovoltaic or grid electricity. It might be possible that your battery storage causes a higher grid draw.

I understand your concerns about client communication. If you like, you could send me your project files here via private message so I can take a look.

Best regards,
Frederik