Grid-Tied Solar With Battery Back-up

Here at our home north of New Denver BC, we have a grid-tied, and battery backed-up system. We bank our extra power on sunny days after the batteries are charged. Should the utility-supplied power go off-line or should the voltage drop below 106 volts as in a Brown-out, the inverter drops the grid connection and acts as an island power source for a chosen set of “critical loads”, like the freezer, the solar hot water heater circulating pump, and several lights and particular wall plugs. For some of you, the well pump circuit and/or the propane furnace might be critical loads. The back-up power here is coming out of standby batteries which are held at full charge. During the outage, the batteries are running critical loads through the DC-AC inverter. When the sun is shining the batteries are being kept charged by solar energy. If it is a stormy and dark time during the power outage electrical loads are running on the stored energy in the batteries. When the power grid is restored, the DC-AC inverter then acts as an AC-DC charger to reestablish full batteries. The size of the back-up batteries dictates how long and how much power can be used during the outage. Manually started generators and automatic starting generator systems (AGS) can be configured into this system adding power reliability in prolonged grid power outages.

When an outage happens, all the power transitions are pretty seamless to you as the power user. The inverters make the power source switching so fast you hardly notice the flicker of the lights and computers are not affected as it only takes 30 milliseconds for the inverter to restore power after the grid power goes down.

You can also have a backup power system without the solar panels and solar charge controller. This system would be recharged either by a restored utility service or a generator. Follow this link: Battery-Based home power system with Generator.

Solar electric systems are PST exempt (7% off ) except batteries are taxable. There are no income tax credits and but for a limited time NRCAN is offering grants up to $5600 for energy audits and solar installations that can include batteries. The best incentive is the hardware costs have plunged as the rest of the world is readily adopting this technology and the economies of scale have made it Oso affordable. In 2022, a good solar site in the Kootenay region will pay for itself in in 15 years and with the grant as little as 7 years for a 5kW system. You can expect service for nearly 20 years on the inverters and 30 years on the modules.

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