Plaid Cymru has taken Caerphilly in a record-turnout Senedd by-election, a result that resets expectations for Wales ahead of May 2026. Lindsay Whittle won with 47% of the vote, Reform UK finished second on 36%, and Labour crashed to 11% on a 50.43% turnout, the highest ever for a Welsh Parliament by-election. The poll was held on 23 October after the death of Labour MS Hefin David in August.

For a seat Labour had held locally for more than a century, third place will sting. Whittle’s victory came despite Reform throwing resources at the contest, with senior figures saturating the campaign. ITV’s count analysis pointed to a near-27% swing from Labour, and to tactical votes coalescing around Plaid to block Reform.

Labour’s setback leaves the party governing with just 29 of 60 Senedd seats for the remainder of this term, narrowing room for manoeuvre on a difficult budget. The numbers also underline Plaid’s momentum and Reform’s growing vote share under the current system-just months before Wales moves to a new proportional election in 2026.

Eco Current readers will see the climate stakes immediately. Key decisions now land within weeks: ministers have tabled regulations setting Wales’s Fourth Carbon Budget ahead of a Senedd vote on 2 December 2025. That package would lock in the next milestones on the path to net zero.

The Climate Change Committee advises setting Carbon Budget 4 at a 73% average emissions cut from 1990 levels for 2031–35, and says the current 2026–30 budget should be met with zero use of international offsets-meaning delivery must happen within Wales. Priority action areas are transport, buildings, and land use.

Progress is real but uneven. Official data show that in 2023 about a third of electricity generated in Wales came from renewables, equivalent to roughly 53% of national electricity consumption when losses are included. Installed renewable capacity inched up, but growth has slowed compared with earlier years.

Infrastructure bodies warn the pace must quicken. The National Infrastructure Commission for Wales notes just 109 MW of new renewable electricity capacity was added in 2023-far below the 2015 peak-and estimates electricity demand could double by 2035, implying generation from renewables must nearly quadruple to hit targets.

There is a route to accelerate. The Crown Estate’s Round 5 awards in the Celtic Sea handed seabed leases to Equinor and Gwynt Glas (EDF Renewables UK/ESB), each planning 1.5 GW of floating wind, with supply-chain studies pointing to more than 5,000 jobs across the region if projects move at speed. First power is expected in the early-to-mid 2030s, so investment and permitting decisions taken now will decide whether Wales captures the benefits.

Party positions matter. Analysis by the Institute of Welsh Affairs highlights that Plaid Cymru backs bringing Wales’s net zero target forward to 2035 and wants energy and Crown Estate powers devolved, while Reform UK argues for scrapping net zero mandates. Plaid’s own programme emphasises a Welsh Green Deal, community energy, and large-scale retrofit to cut bills and emissions.

With the 2026 Senedd election switching to a 96‑member, fully proportional closed‑list system, coalition politics is likely. That raises the odds that climate policy will be shaped at the negotiating table. For campaigners, councils and employers in south Wales, the next six months are an opening to line up retrofit bids, skills programmes, and port upgrades that make clean industry and cheaper energy tangible on the ground.

Back in Caerphilly, the arithmetic tells its own story: Plaid’s 15,961 votes topped Reform’s 12,113, with Labour on 3,713. Smaller parties were left in the low hundreds. A high‑engagement contest produced a clear call for change; what happens next will be measured in heat pumps fitted, buses electrified, and offshore turbines built-not just votes tallied.