Cost of revenue – provision for loss contracts related to service. The Company also recorded a provision for loss contracts related to service of $2.1 million for the three months ended March 31, 2022, compared to $1.5 million for the three months ended March 31, 2021, related primarily to new service contracts entered into during the first quarter of 2022.
Cost of revenue – Power Purchase Agreements. Cost of revenue from PPAs includes depreciation of assets utilized and service costs to fulfill PPA obligations and interest costs associated with certain financial institutions for leased equipment. At March 31, 2022, there were 77 GenKey sites associated with PPAs, as compared to 50 at March 31, 2021. Cost of revenue from PPAs for the three months ended March 31, 2022 increased 73.1%, or $13.4 million, to $31.8 million from $18.3 million for the three months ended March 31, 2021 due to the increase in units and sites under PPA contract as well as certain inflation and COVID-19 related issues such as increased freight costs and scrap charges associated with certain parts. Gross loss increased to (216.4%) for the three months ended March 31, 2022, as compared to (134.4%) for the three months ended March 31, 2021 primarily due to certain inflation and COVID-19 related issues, such as increased freight charges, and scrap charges associated with certain parts.
Cost of revenue – fuel delivered to customers and related equipment. Cost of revenue from fuel delivered to customers and related equipment represents the purchase of hydrogen from suppliers that ultimately is sold to customers and costs for onsite generation. Cost of revenue from fuel delivered to customers for the three months ended March 31, 2022 increased 77.4%, or $17.1 million, to $39.3 million from $22.1 million for the three months ended March 31, 2021. The increase was primarily due to higher volume of hydrogen delivered to customer sites as a result of an increase in the number of hydrogen installations completed under GenKey agreements, inefficiencies in fueling systems and higher fuel costs. As a result of these inefficiencies and higher costs, gross loss increased to (192.5%) during the three months ended March 31, 2022, compared to (99.0%) during the three months ended March 31, 2021. We expect higher hydrogen molecule costs to continue at least through 2022.
Expenses
Research and development expense. Research and development (“R&D”) expense includes: materials to build development and prototype units, cash and non-cash stock-based compensation and benefits for the engineering and related staff, expenses for contract engineers, fees paid to consultants for services provided, materials and supplies consumed, facility related costs such as computer and network services, and other general overhead costs associated with our research and development activities.
Research and development expense for the three months ended March 31, 2022 increased $10.7 million, or 110.0%, to $20.5 million, from $9.7 million for the three months ended March 31, 2021. The overall growth in R&D investment is commensurate with the Company’s future expansion into new markets, new product lines, acquisitions and varied vertical integrations.
Selling, general and administrative expenses. Selling, general and administrative expenses includes cash and non-cash stock-based compensation, benefits, amortization of intangible assets and related costs in support of our general corporate functions, including general management, finance and accounting, human resources, selling and marketing, information technology and legal services.
Selling, general and administrative expenses for the three months ended March 31, 2022, increased $55.3 million, or 216.2%, to $80.9 million from $25.6 million for the three months ended March 31, 2021. This increase was primarily related to increased headcount, which resulted in increased salaries and stock-based compensation, as well as branding expenses.
Contingent consideration. The fair value of the contingent consideration related to the Giner ELX, Inc., United Hydrogen Group Inc, Frames, Applied Cryo and Joule acquisitions was remeasured as of March 31, 2022, which resulted in a $2.5 million and $0.8 million charge for the three months ended March 31, 2022 and 2021, respectively.
Interest income. Interest income primarily consists of income generated by our investment holdings, restricted cash escrow accounts, and money market accounts. Interest income for the three months ended March 31, 2022 increased