In 2018, Acumen raised $36.7 million in philanthropic capital, an increase of 22.5% from 2017. Of the $36.7 million, $7.8 million represents grants to fund our Pioneer Energy Investment Initiative which seeks to bring off-grid energy solutions to the world’s poor. Acumen recognized non-cash revenue of $1.7 million, mostly in the form of donated legal services, primarily to support our investing work.
We received $0.5 million in interest income from portfolio loans and recorded a provision of $2.5 million for portfolio investment losses. Acumen carries our program investments at cost, and we lower these valuations when impairment exists. We review our portfolio of assets on an annual basis and apply a consistent valuation philosophy across the companies in our portfolio. Because we carry these investments at cost, we do not mark up our equity investments to fair market value, even when subsequent funding rounds imply an increase in the holding value of our investments. Any increase in value of equity investments would be recognized as realized gains or profits upon exit.
Operating expenses represents all the direct costs related to the running of Acumen programs as well as our management and general and fundraising costs. They do not reflect any of our investments in our portfolio companies. Total expenses for 2018 were $23.7 million, a 10.7% increase compared to the prior year. Donated services expenses (a direct offset to In-kind contributions) comprise $1.7 million. Our increases reflect growth in a number of our program areas including our Portfolio team, our Leadership Fellows programs, and our +Acumen course offerings.
Program work constitutes 73.6% of our total expenses. Portfolio expenses were $7.9 million, representing the cost of sourcing, due diligence, planning and the execution of $5.8 million in new and follow-on investment disbursements, as well as managing our active portfolio of 83 companies. Outreach, Impact and Communications expenses were $7.4 million, representing our work in measuring and reporting our investment performance (both financial and non-financial), and in the research and sharing of our insights gleaned from our programmatic work. Our Leadership Fellows program expenses were $2.1 million, a decrease of 7.7% from 2017. Fundraising costs and Management and General expense accounted for $6.3 million, which included investments in improving organization efficiency and effectiveness.