One of the most frustrating questions to encounter when talking to homeowners about the merits of going solar is, “what happens when the power goes out?” This question, which is often phrased more as a statement with an inflection at the end – “the system works when the power goes out?” – can kill a deal and is a terrible limitation of most grid-tied solar systems. When the grid goes down most inverters disconnect in order to avoid sending potentially deadly electricity into the power lines while somebody is working on them.
Until recently most inverters, which convert variable direct current to utility frequency alternating current, have been one of two kinds, stand-alone inverters that draw energy from batteries charged by a solar array not connected to the grid and grid-tied inverters, which match phase with the utility sine wave and automatically shut off if the power goes out.
The benefit of grid-tied inverters is that they allow homeowners to take advantage of net-metering policy, which mandates that utilities credit their customers whom produce electricity that they do not use and instead flows back into the grid. Solar systems are most productive during the early afternoon when people are typically at work and using little electricity, so to be able to accumulate credit when systems are over producing relative to the household demand is key to making solar financially attractive.
The benefit of stand-alone inverters is that they will provide electricity as long as the sun shines and charges the batteries. These inverters are traditionally used when the option to connect to the grid doesn’t exist and require batteries, which increase the cost of the system by about 25%.
Now, however, companies like SMA Solar Technology, Outback Power and some up and comers, are putting an end to the unease sales folks feel when they inevitably get the blackout question by giving them a financeable and affordable solution to offer homeowners.
The Sunny Island, by SMA, allows for a host of different scenarios, from off-grid PV only systems, to off-grid generator only systems, to grid-tied battery backup systems to grid-tied PV systems with battery storage. You can scale the number of Sunny Island inverters and batteries to meet almost any household electricity need and with the right sized solar system you can be fully functional for months, regardless of what’s going on with the grid.
The GTFX and GVFX are Outback’s answer, capable of selling power back to the local utility, yet outfitted with a built in transfer switch that will automatically disconnect the house load from the grid if the power fails and seamlessly allow you to use your stored energy.
Other companies, like Sunverge Energy, have taken one step further and include home energy monitoring (HEM) systems, so that you can generate and store electricity, operate when the grid goes down, and monitor, allocate and control usage and charging schedules to take advantage of peak demand pricing, as well as help support grid stability by either accepting or discharging energy when needed. Basically these systems allow you to be your own utility when the powers out and support your local utility when its not. Oh, and did I mention it’s controlled by software running on the cloud and manageable via your smart phone? This truly is the future of electricity generation and management.