May 31, 2023
This article initially appeared within the Q1 2023 version of Solar Builder journal. Be certain to get your individual free print and/or digital subscription proper right here.
When I first began working within the PV business within the mid-2000s, the brand new sector of grid-tied PV installer actively prevented costly and sophisticated lead acid battery programs that had been generally utilized in off-grid home purposes. Since the typical family loses power for lower than 10 minutes per yr, few solar contractors felt that battery backup made any sense in any respect for grid-tied solar homeowners.
But instances have modified. Lithium batteries have eradicated the excessive value and complexities of older lead acid battery programs and more and more frequent power outages in California and Texas have pushed solar householders to hunt out battery options to offer backup power and energy independence. Additionally, new time of use utility charges that improve night kWh charges and scale back the worth of a backfed kWh through the sunny hours of the day have led solar homeowners to cost their very own batteries through the day and use the kWh within the night to save cash.
Unfortunately, I see far too many utility errors when contractors design and set up battery programs for grid-tied prospects. One of the largest issues is that everybody desires to again up their total home, however few folks have the large finances to permit them to buy a battery system large enough to again up all the masses in a contemporary home.
Sadly, too many solar gross sales folks and contractors are promoting 10 to twenty kWh battery programs and configuring them for “whole home backup.” When the following power outage happens, most householders uncover to their dismay that their inverter can not power the entire hundreds of their home, and it stalls out or, if the inverter doesn’t shut off as a result of overload, the battery drains rapidly when the air-con and/or scorching water heater kick on. Only then do they notice that entire home backup means power for a number of hours, after which no extra power for lights, a fridge and different important hundreds till the solar costs the system once more.
Over 90% of house owners who need batteries with their solar system are finest suggested to have a partial load backup configuration. This usually includes putting in a particular backed up sub panel and relocating the load breakers which are increased precedence. These increased precedence hundreds usually embody lights, computer systems, medical gear (CPAP machines), fridges and storage door openers.
The load circuits deemed as important will differ from one area to a different and one household to a different, in fact. In areas with wells, a properly pump is an enormous load that’s seemingly important to each day life. Others may discover sump pumps to be a important load, and others may discover a window AC unit important for getting sleep on scorching nights. In Texas, many owners have understandably backed up their furnace blower fan so their gasoline heaters proceed to function when the grid goes down.
As a common rule, scorching water heaters, swimming pool pumps, central air conditioners and EV chargers are too power intensive and can seemingly stall out the inverter for battery programs, or they are going to drain your battery too rapidly.
Just to make use of an instance, my 2,600 sq ft Phoenix space home with two 4-ton AC models and a swimming pool pump will use a mean of 70 to 80 kWh per day in the summertime. To again up all my hundreds in the summertime would seemingly require a 100 kWh battery system costing from $70,000 to $100,000. Even if I had the funds to purchase a battery this huge, discovering appropriate area for a system this huge could be troublesome.
Therefore, the most suitable choice is making the arduous resolution of which hundreds to rewire to a backed-up load panel.
There is a brand new expertise that’s rising the flexibleness for powering houses in a grid outage. Demand load controls from Lumin, Span, Savant, Generac and others are permitting solar + storage programs to power the complete home load panel and allow management over which breakers to power off in a grid outage.
When the grid goes down, these controllable breaker circuits will usually be programed to power off your AC system, water heater, electrical vary, washer and dryer, dish washer, swimming pool pump, and another noncritical load. The lights, fridge and regular plug shops will stay energized by your battery.
However, a few of these noncritical hundreds might have to be run off battery power. A very good instance is a front-loading washer. If you endure a grid outage when working a load of laundry in a entrance loader, the machine will sit there, stuffed with water till power is restored. This might lead to a washer stuffed with moldy clothes if the power outage lasts a number of days.
Using demand load management, you’ll be able to override the default programming and instruct the system to permit your washer to run on battery power lengthy sufficient to complete the load of laundry and hold the moist garments to dry. These new demand controls are getting smarter and extra useful, permitting integration with thermostats to intelligently and correctly power down AC programs and warmth pumps and handle your battery power.
Partial load or load management?
If the venture finances permits addition of a load controller, it’s potential (and infrequently fascinating) to configure the ESS for entire home backup. Here are a number of choices value contemplating.
■ Generac’s PWRmanager automates management of as much as twelve 120V circuits or six 240V circuits, plus two thermostats, and it integrates seamlessly with the PWRcell System and PWRview app in order that householders can swipe any circuit on or off and see how a lot battery run time they’ve left consequently. Learn extra on this episode of The Pitch:
■ The Lumin Smart Panel has 12 controllable circuits (six 60A and 6 30A) and prices about $2,500 plus set up value. For most tasks, that is a straightforward couple-hour set up. This system is adequate for many houses, however bigger houses might have a extra sturdy answer like a Span panel.
■ The Span panel replaces an current load heart and makes all breakers controllable. It is dearer (beginning at $4,500+), and the set up is extra concerned since you’ll most likely be changing the present major load heart. Anticipate 4 to eight+ hours (~$2,000 – $5,000) for labor to put in and certain coordination with the utility to close off service throughout set up. A brand new meter/major model of the Span panel is coming quickly, however as of this date, the UL itemizing is just not but accessible. Since meter mains might be troublesome to make use of with ESS, I anticipate this is not going to be essentially the most sensible possibility for ESS.
■ Savant load management modules are put in proper within the breaker slots of many frequent panel boards and are fairly priced. One of their extra frequent load management module packages for 8 circuits is priced underneath $1,000 and would require about 3 hours of set up time. Keep in thoughts the Savant management modules have to be put in in a panelboard, so chances are you’ll must unlock breaker areas by utilizing twin or quad breakers, and even higher, set up a subpanel to accommodate all of the load breakers and the Savant load management modules.
Important notice: Not all ESS programs have adequate power (kW) and energy (kWh) to help hundreds aside from essentially the most primary backup of fridge, lights, wall shops and storage door opener, so relying on the variety of hundreds and their measurement, a partial load backup should still be advisable for programs lower than 7,000 W output or lower than 10 to twenty kWh.
Backup wrap up
As a results of the elevated demand for resilience and energy independence, the solar installer of yesterday is morphing right into a solar + storage installer. This evolution will proceed with contractors turning into home energy service suppliers, integrating solar, storage, demand management, mills, EVs and different management programs. Homeowners will be capable to management their energy prices and effectively handle battery use when the grid goes down whereas permitting life to proceed with minimal interruptions.
Jeff Spies is the president of Planet Plan Sets, a solar plan drafting firm serving contractors in all 50 states. He is a board member and secretary for NABCEP, a UL 2703 and UL 9540 Standard Technical Panel member, a founding member and previous secretary for the Sustainable Energy Action Committee (SEAC) and chairs the Codes/Standards committee for the California Solar and Storage Association (CALSSA).
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Tags: Generac, load management, Lumin, Savant Power, Span