William Harnisch Peconic Partners
William Harnisch is the founder of Peconic Partners, a concentrated investment firm known for high-conviction equity positions. The firm’s portfolio often differs sharply from broad market benchmarks, reflecting a willingness to concentrate capital. Harnisch’s disclosures are tracked by investors interested in bold, research-driven concentration.
Top Buys
| Rank | Stock | Value |
|---|---|---|
| 1 |
MasTec
MTZ
|
+$178M |
| 2 |
Freeport-McMoran
FCX
|
+$86.7M |
| 3 |
Amazon
AMZN
|
+$68.6M |
| 4 |
First Solar
FSLR
|
+$49.2M |
| 5 |
Cinemark Holdings
CNK
|
+$10.5M |
Top Sells
| Rank | Stock | Value |
|---|---|---|
| 1 |
Shoals Technologies Group
SHLS
|
+$52.3M |
| 2 |
Warner Bros
WBD
|
+$19.5M |
| 3 |
Array Technologies
ARRY
|
+$17.4M |
| 4 |
Dycom Industries
DY
|
+$2.84M |
Sector Composition
| Rank | Sector | Weight |
|---|---|---|
| 1 | Industrials | 91.48% |
| 2 | Materials | 2.41% |
| 3 | Energy | 2.17% |
| 4 | Technology | 1.92% |
| 5 | Consumer Discretionary | 1.67% |
| Name | Market Value | Portfolio Weight | Shares or Principal |
Change in Stake | Capital Flow | |
|---|---|---|---|---|---|---|
1
Quanta Services
PWR
$96.1B
| $2.11B | 50.23% |
5,007,840
| – | – |
|
|
2
Dycom Industries
DY
$11.8B
| $1.39B | 32.99% |
4,108,320
-9,000
| -0.2% | -$2.84M |
|
|
3
MasTec
MTZ
$21.4B
| $348M | 8.27% |
1,600,000
+850,000
| +113% | +$178M |
|
|
4
Freeport-McMoran
FCX
$110B
| $102M | 2.41% |
+2,000,000
| New | +$86.7M |
|
|
5
First Solar
FSLR
$23B
| $77.1M | 1.83% |
295,000
+195,000
| +195% | +$49.2M |
|
|
6
Amazon
AMZN
$2.79T
| $70.2M | 1.67% |
303,980
+300,000
| +7,538% | +$68.6M |
|
7
EQT Corp
EQT
$33.6B
| $31.1M | 0.74% |
580,000
| – | – |
|
8
Range Resources
RRC
$9.59B
| $28.2M | 0.67% |
800,000
| – | – |
|
9
Devon Energy
DVN
$54B
| $11M | 0.26% |
+300,000
| New | +$10.5M |
|
|
CTRA
10
DELISTED
Coterra Energy
CTRA
| $10.5M | 0.25% |
+400,000
| New | +$10.1M |
|
11
Antero Resources
AR
$11.7B
| $10.3M | 0.25% |
+300,000
| New | +$10.2M |
|
|
12
Cinemark Holdings
CNK
$4.24B
| $9.3M | 0.22% |
+400,000
| New | +$10.5M |
|
13
AMC Entertainment Holdings
AMC
$2.28B
| $4.68M | 0.11% |
3,000,000
+1,000,000
| +50% | +$2.38M |
|
14
Silicon Laboratories
SLAB
$7.27B
| $3.92M | 0.09% |
+30,000
| New | +$3.94M |
|
15
Alphabet (Google) Class A
GOOGL
$4.22T
| $563K | 0.01% |
1,800
| – | – |
|
|
16
Array Technologies
ARRY
$722M
| – | – |
-2,130,783
| Closed | -$17.4M |
|
|
17
Shoals Technologies Group
SHLS
$1.19B
| – | – |
-7,054,803
| Closed | -$52.3M |
|
|
18
Warner Bros
WBD
$71.6B
| – | – |
-1,000,000
| Closed | -$19.5M |
|
Similar funds
William Harnisch's Q4 2025 Portfolio in Review
As of Q4 2025, William Harnisch held 18 positions worth $4.21B, up 16% from $3.62B the previous quarter. Its ten largest holdings account for 99% of the portfolio.
William Harnisch deployed $338M of net new capital in Q4 2025, opening 6 new positions and adding to 4 existing holdings. Its largest new stake was Freeport-McMoran: 2,000,000 shares worth $102M.
By sector, the portfolio is most concentrated in Industrials at 91% of assets, down from 95% a quarter earlier, followed by Materials and Energy.
On the sell side, the largest reduction was Dycom Industries, an estimated $2.84M trimmed.
- William Harnisch's largest Q4 2025 buy was Freeport-McMoran: 2,000,000 shares worth $102M.
- William Harnisch added most to MasTec in Q4 2025, an estimated $178M increase.
- William Harnisch's biggest Q4 2025 reduction was Dycom Industries, cutting an estimated $2.84M.
- William Harnisch fully exited Shoals Technologies Group in Q4 2025, selling an estimated $52.3M.
- William Harnisch's ten largest holdings make up 99% of its $4.21B portfolio in Q4 2025.
- William Harnisch opened 6 new positions and closed 3 in Q4 2025.
- William Harnisch's portfolio value rose 16% quarter-over-quarter to $4.21B.
Based on Peconic Partners's 13F filing for Q4 2025, filed 17 Feb 2026.