From my experience, solar alone can be an inconsistent source of electricity for a fan that must be on 24 hours/day (as soon as the sun goes down or it gets too cloudy the system stops). But, it is possible if you connect a few batteries to the system to overcome this; during the day the solar panels recharge the batteries, and at night the fan continues to run off the batteries. Although, from my calculations, the ROI is simply not there, especially if you consider the routine maintenance and inspections required of these systems.

If anyone else has found radon mitigation fans that run off renewable energy, i would be very interested too. Thank you.

I wanted to develop a solar-powered fan a few years ago, and discussed it with my neighbor who installs solar systems. Bottom line is that it is possible, but not practical. I envisioned a 4-6" sq. solar panel on top of the fan, like a landscaping light, but it turned out the panel would need to be about 3' square, and with the necessary storage batteries for night time and cloudy days, the setup would run about $3500.

I attended a Vapor Intrusion training a number of years ago where Bill Brodhead was looking at it for new construction. Sealing was extensive, so only a very low power fan was needed. Of course VI economics are different than for radon mitigation.

Things have changed with new low voltage fans and cheaper solar panels since we discounted solar. I just did some quick calculations which are likely to be way off but here is what I figured. Using RadonAway's new LV175 24 volt radon fan as an example. It uses 30 to 71 watts at 120 volts via the 24 volt converter. That is about a maximum of 0.6 amps at 120 volts. At 24 volts it would be using about 15 watts. You can buy a Renogy 5'5"X3'3" 24 volt 270 watt panel for $300. You can also buy two deep cycle 25 pound 12 volt 300 AH batteries for about $150 and wire them for 24 volt. You would also need some voltage regulator to keep the batteries from over charging. The solar panel would easily run the radon fan. Two batteries should keep the fan running for 2 days when no sun. And the solar panels at full capacity are putting out 11 amps at 24 volts so theoretically they could re-charge the batteries in 6 hours of bright sun. Besides the fan that makes the basic solar materials about $500. Maybe others can correct my conversions