Beyond South-Facing Yield: Designing Zurich PV for Winter Electricity Value / Our Blog / By admin On the south-facing default We’re all familiar with the same rule of thumb: point it south, tilt it around 30-35 degrees, chase the highest annual kWh number you can get. Back when a kWh in July and a kWh in January were worth roughly the same to the client, this fared fine. Definitely not now. And the gap gets wider. Swiss spot prices sag toward zero. Even below it sometimes, on summer afternoons when half the country’s rooftops are dumping power onto the grid at once. Winter prices keep climbing as the grid leans harder on solar to fill a gap it can’t fill in December. The Winterstrombonus kicked in for systems commissioned from January 1. It pays a one-time CHF 3.50 per kWh of winter output above 500 kWh/kWp. Most flat, south-facing Plateau installs never get close. So we’ve got a situation where the metric everyone was trained on (maximize annual yield), sort of works against the client’s financial interest. A kWh produced in January is worth more than the same produced in June. Both on the market and now through direct subsidy. We’re leaving money on the table if we keep designing for the summer curve. Why the standard tilt falls short in winter Around Zurich, the winter sun barely clears 20 degrees above the horizon. Meanwhile a 30-35 degree tilt is built to catch high summer sun, not that. Typical Plateau systems land somewhere around 250-300 kWh/kWp for the winter half-year.Compare that with what steep/vertical bifacial setups do at Swiss test sites today: 60° monofacial modules: ~743 kWh/kWp in winter 60° bifacial: around ~889 kWh/kWp 90° vertical monofacial: winter output making up 55% of total annual yield, vs roughly 25-40% for a standard flat-tilt roof The reason is pretty clear once you see it. Steep panels face low winter sun head-on instead of glancing off it. And if there’s snow on the ground, near-vertical bifacial modules pick up a decent amount of reflected light off its back. That’s where the reported “winter boost” comes from. What this means on a real roof You’re not usually building a greenfield alpine array. You’ve got an existing roof, maybe a facade, and a budget. Put this through the winter lens: Ask which orientations get the system past the winter threshold without getting the annual number too low. And facades stop being a fallback option. Now they’re genuinely useful for winter production. A vertical bifacial facade can stack the GREIV integration bonus on top of the Winterstrombonus if it clears 500 kWh/kWp. Big roofs don’t need one uniform tilt. Split it: A steeper section (45-60 degrees) doing double duty on winter yield and snow shedding A flatter section left alone for the summer/annual number Modeling the blended winter fraction, not just total kWp installed Bifacial as a starting point. On a light membrane roof or anywhere with reliable snow cover, a 5-12% bifacial gain on flat roofs is enough now to specify by default. Price against the whole incentive stack. Potentially, a design that clears the winter threshold can combine: The Winterstrombonus Cantonal top-ups Standard feed-in revenue (it’s already moving toward quarterly and eventually hourly pricing) What we’re telling clients this year Don’t default to just a south-facing tilt on new Plateau projects. Run the winter fraction and see where it lands. If you’re above ~30 kWp and targeting 2026 or later, check if a steeper or facade-integrated sub array gets you over the 500 kWh/kWp line. Hourly spot pricing kicks in, Jan 2027. Winter-strong systems will feel the upside first. On the Plateau this has become a pretty basic design question. Certainly not an alpine niche anymore. Steeper designs might generate fewer total kWh over the year. It can still make the client more money. Because more of that output lands when the price curve and now the bonus, actually reward it.
