Sizing tools
Free, no signup. Four steps size a system and add it up; numbers carry from one tool to the next, kept in your browser only.
- What do you need to run?
Pick your appliances - typical running, surge and idle watts are filled in - and get daily watt-hours, peak load, battery bank and inverter size.
You get: Wh per day · battery kWh · inverter W
- How much sun do you get?
Peak-sun hours for your ZIP code, year-round, summer and winter, with the tilt to use. Turns your daily Wh into the number of panels you need.
You get: sun hours · tilt · panels needed
- How many panels can you actually install?
Your inverter sets a minimum and a maximum number of panels per string (and total), and your roof or yard sets a hard ceiling. Find all three and the number you can build.
You get: min / max per string · inverter limit · what fits
- What does that add up to?
The panels, inverter and battery your numbers point at, in one list you can print or link to - plus the wire, fusing, disconnects and mounting the install still needs.
You get: parts list · where to buy · what else you need
Quick converter
- Watts, volts, amps & time
Enter any two of W / V / A and a run time. Get the third, plus Wh and Ah at 12, 24, 48, 120 and 240 V. Handy any time you are reading a label.
Planning figures, not a design. These calculators give you ballpark numbers to shop and plan with. They are not an electrical design, they cannot see your site, your loads or your local code, and they may be wrong. Wire sizing, over-current protection, grounding, rapid shutdown and interconnection must follow NEC 690 and your local code. Have any design checked by a licensed electrician before you buy or energize anything. You use these tools at your own risk.More on safety.