Solar design of the day
A new roof, a competitor's bid 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 in that city's weather
Open-circuit voltage at the city's ASHRAE extreme minimum stays under 600 V (NEC 690.7). Maximum-power voltage at the 2% design high plus 30 °C stays above the MPPT minimum, and on the coldest day under the MPPT maximum. 1.25 × Isc stays under each input's short-circuit rating, the conservative NEC 690.8 value.
Every panel needs rapid shutdown
NEC 690.12 needs the conductors in a roof array brought under 80 V within 30 seconds. On a string inverter that means an optimizer or a rapid shutdown device on every panel, and add-on optimizers can share a transmitter with RSDs. Microinverters have it built in, if the panel is within their listing.
The busbar decides how big you go
The main breaker plus 125% of the inverter's output current has to fit inside 120% of the busbar rating, with the PV breaker at the opposite end from the main (NEC 705.12). If it doesn't, derate the main when the load calculation and the 100 A dwelling minimum allow it, tap the supply side where the utility allows it, or upgrade the panel.
Fire setbacks come first
Every slot already keeps 18 in from the ridge and leaves a 36 in pathway. If the array covers more than 33% of the roof plan (66% with sprinklers, which these houses don't have), the ridge setback becomes 36 in and the top row is out (IRC R324.6).
Scored out of 100
Beat the competitor's bid 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, strings it to the inverter and estimates the year's production, on the same job as the site survey, proposal and permit paperwork. So the design your team approves 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 clear, broken-cloud and overcast days, in the proportions that suit its climate. Direct and circumsolar light are traced past every tree, the chimney and the house to each panel, and 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 behavior and inverter clipping.
No. It's a game built on a simplified physical model, and the kit and prices are fictional. It leaves out options like a UL 3741 PV hazard control system and power control systems (705.13). Your AHJ, its adopted NEC and fire code editions, and the utility all have the final say. For a homeowner estimate on a real roof, use the solar panel output calculator, which uses PVWatts data.
Check its maximum input short-circuit current. 1.25 × a high-current panel's Isc can be more than an older micro is listed for, and then the pairing isn't allowed however good the price is.
Because that's how a design goes out in real life. You can practice 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 panel output calculator