The importance of less than 100% reliability

From How to Build a Low-tech Website:

In contrast, this website runs on an off-the-grid solar power system with its own energy storage, and will go off-line during longer periods of cloudy weather. Less than 100% reliability is essential for the sustainability of an off-the-grid solar system, because above a certain threshold the fossil fuel energy used for producing and replacing the batteries is higher than the fossil fuel energy saved by the solar panels.

The “less than 100% reliable” design pattern is a powerful one.

I get pinged on my mobile phone, for example, if this website goes down. But only between 7:00 a.m. and 11:00 p.m.

I could hire a antipodean doppelganger to keep the watch in small hours, but the risk-reward of that wouldn’t be worth it. If MySQL crashes at 3:00 a.m., y’all are on your own until I wake up.