If you’re on-grid, energy efficiency is important. It saves you dollars and reduces your environmental footprint. But it’s even more important if you’re off-grid—or planning to move off-grid.
Renewable energy (RE) systems generally produce electricity that is more expensive than heavily subsidized grid electricity, with all its socialized costs and impacts. The utility grid also provides you with essentially unlimited electricity 24/7/365, without a need for storage. This makes renewable electricity seem expensive by comparison (though it really isn’t if you look at the big picture).
Off-grid RE systems must provide for all the electrical energy you want, day or night and no matter the weather. There can be several consecutive days with little sun or wind—and even when it is sunny or windy, you need a buffer between your energy sources and your energy loads. This means a battery bank, which is costly and also limited in capacity. Your backup for when energy production and the battery is low is not the utility grid, but usually a noisy, polluting, and expensive fuel-fired generator.
All of this is why, in 1984, at a time when I was not accustomed to spending thousands of dollars on anything, I bought a $2,500 refrigerator. This was shocking to my on-grid neighbors, who couldn’t imagine why I would spend so much on an appliance, when nothing else on my property had cost that much.
The explanation was clear: If I had purchased the lowest-cost fridge from the local appliance store, I would have had to spend many more thousands of dollars on additional RE gear to power the initially cheap—but lower efficiency—fridge. Energy efficiency is often the best investment you can make, if you take the long-term view.
My fridge is direct current (DC), a choice I might or might not make today (and would be much less likely to make for a client). Going with DC avoids the losses inherent in an inverter, which converts PV and battery DC to conventional alternating current (AC)—the electricity type most people are used to. This makes a simpler system in some ways, since the batteries are tapped directly.
When I started with RE, efficient inverters were non-existent. So my home still uses a lot of DC. The drawbacks to this strategy are that DC is not conventional, so it’s not always easy to find appliances, and some appliances—made for the RV and marine industry—are not as efficient or robust as their AC counterparts.
The other drawback is that you’ll typically end up with dual household wiring systems, because very few people can live with only DC. Most often, AC appliances are also desired, which means having two sets of wiring (DC and AC), a more expensive option. Usually the wisest choice for a modern, whole-house system is to choose all AC, buy an efficient inverter, use ultra-efficient appliances, and add a bit more energy capacity to the system to cover the inverter losses.
For large residential RE systems, small phantom loads (appliances that use energy when “off,” or for no useful purpose) are not necessarily a big deal. It’s important from an environmental point of view to reduce or eliminate them, but they are not deal-breakers when the grid or large renewable generating capacity is available.