Solar design of the day
A new roof, a competitor's quote and a budget. Win the job.
Live sun and shade · Scored out of 100 · Daily leaderboard
Drawing today's roof…
Checked the way a real design is
Every submission is re-scored on our side against the same rules.
Every string has to pass on the worst days
Open-circuit voltage on a −10 °C morning stays under the inverter's DC limit. Maximum-power voltage at 70 °C cell temperature stays above the MPPT minimum, and at −10 °C under the MPPT maximum. 1.25 × Isc stays under each input's short-circuit limit.
The DNO and the diary are real constraints
The install has to happen in four weeks on a single-phase supply. Anything over 3.68 kW needs G100 export limitation to go through a fast-tracked G99 application.
Shade drags the whole string
Without optimisers, a shaded panel's bypass diodes cut in and the string runs at the current that suits most of it. Optimisers fix that panel by panel, at a price.
Scored out of 100
Beat the competitor's quote and win the job and you score 50. Match the best design our solver found for the day and you score 100. A sharp design can beat our best and go past 100.
Glow, limited release
Get every design right before it reaches the roof
Glow lays out the customer's real roof from satellite imagery and strings it to the inverter, on the same job as the survey, proposal and MCS paperwork. So the design your team signs off is the one that gets installed.
Solar design of the day, explained
Each puzzle runs an hourly sun path for the city's latitude across a clear, a broken-cloud and an overcast day in every month. Direct and circumsolar light are traced past every tree, the chimney and the house to each panel; the rest of the sky is reduced by how much of it each obstacle blocks. Output is calibrated so an unshaded south-facing 35° roof matches typical yields for that city, then derated for cell temperature, string behaviour, inverter clipping and any export limit.
No. It's a game built on a simplified physical model, not the MCS MIS 3002 method, and the kit and prices are fictional. For a customer estimate on a real roof, use the solar yield calculator, which uses MCS irradiance data.
Bare branches let roughly half the light through, while a tree in leaf lets through around a fifth. Scrub the month slider to December and the same oak casts a longer shadow but a thinner one.
Because that's how a design goes out in real life. You can practise on earlier days as much as you like, and our best design opens for every day once it's over.
Your first name, initial and score, if your design wins the job and you confirm by email. Only the top 10 show, and equal scores go to the cheaper system, then the faster time. Your company and email are never published, and you still see your own rank.
Estimating a real roof? Use the solar yield calculator