While estimates vary based on demand and solar conditions, a typical recommendation for a solar and storage system for the average American household of 2.5 people is 8kW of PV and 30KWh of battery capacity. (If you don’t believe us, see this link for reference or ask your local solar installer.)
By contrast, the DC Microgrid at Living Energy Farm supports 10 people with 2.5kW in PV capacity. Per capita, that’s 8% of the PV estimate quoted above. However, we also have 150 square feet of flat plate thermal collectors, which brings the total to 8kW equivalent (PV and thermal collectors are not really the same, but this is a ballpark estimate). That’s 25% of the solar collectors needed for conventional off-grid systems.
But the real difference comes with comparing the battery demand. At Living Energy Farm, 3 kWh in total battery capacity supports the electrical storage needs for 10 people. Crunch the numbers and you’ll see that D3M reduces battery demand by a shocking 97.5%, compared to conventional solar and storage. And keep in mind that conventional solar and storage systems rely on lithium batteries that must be replaced every 5-10 years. The nickel iron batteries used at LEF will last for many decades. (Our oldest battery set has been in service for 14 years with no decline in output.)
Of course, a lot of what makes these numbers impressive comes down to the number of people served. But that’s not just an accounting trick, it’s a reflection of the laws of physics and economies of scale. For thermal loads, particularly in cold climates, the per capita cost and complexity declines dramatically as systems are shared. What makes renewable energy affordable, for both people and the planet, is community.
Ignoring thermal loads – let’s say you live in the tropics, or you’re planning to burn a lot of firewood – D3M still has a significant edge over conventional solar and storage, but sharing systems becomes less critical.