Cool it, power it.

Size solar, batteries and air conditioning for homes and hotels, from the customer's bills or from a building plan. Show the options, then hand over a proposal.

Start with the customer, the city and the bill.

Is solar worth it for this house?

      Your house in the sun

      Drag to turn · scroll to zoom
      SolarBatteryGridMore dots = more power

      A typical day, hour by hour

      Battery level

      Shaded columns are night. Tap or drag on the chart to move the sun in the 3D view. The order never changes: solar runs the house first, extra solar fills the battery, the battery runs the house when the sun is gone, and the grid steps in only when the battery reaches its backup reserve.

      Air conditioning size

      Cooling

      Where the heat comes from at the hottest hour

      Which system to buy

      Room by room

      Quick AC rules per m²

      For a site visit

      Fast checks to do in front of the customer. Type in one room and the size updates as you type. These rules look only at size and a few adjustments, so use the room-by-room calculation for top floors, big glass and hotels.

      Cooling: rules of thumb

      Heating: rules of thumb

      Units

      Where your electricity goes

      Before solar

      Month by month

      Solar panels and battery

      Best value

      How one panel turns sunlight into power

      25-year value vs number of panels

      Value is in today's money: 25 years of bill savings, discounted, minus the up-front cost and one battery replacement at year 15. The top of the curve is the best-value size. Panels go on the sunniest roof face first.

      Where your power comes from each month

      Battery storage

      Savings, evenings, backup

      Three ways to size it

      Backup during an outage

      During a power cut
      Fridge, lights, Wi-Fi, a few outlets ≈ 0.5–1 kW on average.

      Inverter

      Money over 25 years

      Where the money stands each year

      Pay with a loan

      What could change the result

      Year-by-year cash flow

      How we calculate, and how professionals do it

      Methods & sources

      Every number on this page comes from a published engineering method. The table names the method, says whether installers and engineers use the same one, and explains where and why we simplify.

      Monthly numbers (table)