If you're a federal employee who started before 1987, you may have had the choice to switch from CSRS to FERS, or you're still under CSRS. If you started after 1987, you're in FERS. Either way, understanding what separates the two systems reveals a lot about what your retirement will actually look like.
The short version: CSRS is a richer, more self-contained defined benefit. FERS is a three-legged stool designed around the assumption that you'll also have Social Security and TSP. Neither is obviously better -- the right answer depends on your specific situation -- but the math is worth knowing.
The benefit formula
CSRS uses a tiered multiplier: 1.5% for the first five years of service, 1.75% for the next five, and 2.0% for every year after that. A 30-year CSRS employee's annual pension is roughly 56.25% of their high-3 average salary.
FERS uses a flat 1.0% multiplier for most retirees, or 1.1% if you retire at 62 or later with at least 20 years of service. A 30-year FERS employee retiring at 62 earns 33% of their high-3. That's roughly 40% less than the equivalent CSRS pension.
The gap looks brutal in isolation. But FERS employees also receive Social Security (CSRS employees generally don't) and can contribute to the TSP with a government match (CSRS employees get only a partial match). The three components together are designed to reach a similar total retirement income -- but only if Social Security is substantial and TSP contributions have been maximized.
The COLA difference
This is where CSRS wins decisively. CSRS retirees receive the full CPI-W increase every year with no cap. In years with 7% inflation, CSRS retirees get 7%.
FERS retirees get a reduced COLA: if CPI is 2% or below, they get the full amount. If CPI is between 2% and 3%, they get exactly 2%. If CPI exceeds 3%, they get CPI minus one percentage point. At 7% CPI, FERS retirees get 6%. At 5%, they get 4%.
The cumulative effect over 25 years is significant. At 3% average inflation, a $40,000 CSRS pension grows to $81,000 in nominal terms. The equivalent FERS pension (assuming the 2% COLA every year at 3% CPI) grows to $65,000. The CSRS retiree is $16,000 ahead by year 25 on the pension alone. Add the periods of higher inflation like 2021-2023, and the gap widens further.
FERS COLAs also don't begin until age 62. If you retire at 57 under FERS, your pension is frozen in nominal terms for five years before any inflation protection starts. That's roughly 15% of purchasing power lost before your first COLA even arrives, at 3% inflation.
Social Security integration
CSRS employees don't pay into Social Security during their federal service and generally don't receive Social Security from that work. If they have private-sector Social Security credits, the Windfall Elimination Provision (WEP) reduces those benefits. The Government Pension Offset (GPO) can eliminate spousal and survivor Social Security benefits for CSRS retirees.
FERS employees pay full Social Security taxes and receive full Social Security benefits (subject to normal rules). For a federal employee with 30 years of federal service and some private-sector history, the Social Security benefit at 67 might be $1,800-$2,400/month. That's a significant addition to the FERS pension that CSRS retirees don't have.
TSP and the match
Both FERS and CSRS employees can contribute to the Thrift Savings Plan. FERS employees receive an automatic 1% employer contribution plus a 4% match on their contributions (up to 5% total). CSRS employees receive only a 5% employer contribution with no match on personal contributions -- making the TSP substantially less valuable for them.
A FERS employee who contributes the full 5% to TSP over a 30-year career, earning average market returns, can accumulate $400,000-$700,000 in TSP depending on salary level. That's a meaningful supplement to the smaller FERS pension. CSRS employees who didn't contribute to TSP (many didn't, since it wasn't the primary retirement vehicle) have only the pension.
The actual comparison
For a federal employee with a $100,000 high-3 salary and 30 years of service:
- CSRS pension at retirement: ~$56,000/year with full CPI COLA from day one
- FERS pension at 62: $33,000/year with partial COLA from age 62
- FERS Social Security at 67: ~$22,000/year with full CPI COLA
- FERS TSP at 65 (annuitized or drawn at 4%): ~$20,000-$28,000/year
Total FERS income at full retirement: $75,000-$83,000/year, with most components growing with inflation. Total CSRS: $56,000/year, fully indexed. FERS wins on total income if TSP was funded and Social Security is substantial. CSRS wins if the federal employee has minimal private-sector SS credits, didn't maximize TSP, or values the simplicity of one fully-indexed income source.