Tesla Motors Inc (NASDAQ:TSLA) has been in partnership with its sister company SolarCity Corp (NASDAQ:SCTY) since 2013 and it appears that their collaboration is starting to bear juicy fruits. Earlier this month, Tesla said in its 14A document that it earned $8 million in revenue from the solar company last year and it expects over five-fold to $44 million this year.

Green Tech Media (GTM) conducted a study on the filing’s details and found that the electric vehicle (EV) company’s estimated sales to SolarCity will be 116MWh, which is 60% more than the entire US behind-the-meter energy storage market of 2015.

The research firm initially shed lights on ‘Certain Relationship and Related Party Transactions – Related Party Transaction – SoalrCity Agreement’ section, which provided information on realized revenue from previous-generation and second-generation storage products from the solar company.

Tesla realized roughly 2.4 million in revenue for previous-generation storage products to SolarCity last year. In April 2013, both the companies entered into a supply agreement under which Tesla supplied SolarCity with previous-gen products. Through this agreement, the automaker recognized revenue of $700,000 from its sister company in 2015. Lastly, the companies joined hands through a ‘master supply agreement’ in December 2015 which resulted in about 4.9 million in revenues for Tesla.

Tesla Energy only offers two products: Powerwall (for households) priced at $430 per kWh and Powerpack (for commercial customers) priced at $250 per kWh. The research firm used the existing data to find the MWh the automaker sold to the solar company.

Taking into account a 5% on higher-volume, long-term agreements, GTM Sr. Energy Storage Analyst Ravi Manghani found that Tesla sold 6 MWh through the $2.4 million revenue realized, 1.8 MWh from the $0.7 million revenue, and 18MWh via $4.9 billion revenue. These makes total of 25.8 MWh of sales to SolarCity.

The EV maker is now expecting $44 million of revenue from SolarCity via the December 2015 agreement, representing 450% or over 5 times growth from the millions of dollars realized last year.

Mr. Manghani even calculated the MWh of energy-storage products Tesla will likely sell to SolarCity, excluding the recent KIUC territory deal for which the company will be providing 13 MW solar PV, along with 13 MW/52 MWh of storage capacity. The analyst’s calculations stood at 116.5 MWh, which could have gone over to 168.5 after including the KIUC project.