Solar + Storage for Homeowners Storage Value Proposition in VA Bac - - PowerPoint PPT Presentation

Solar + Storage for Homeowners

Storage Value Proposition in VA

Bac ackup up Power er for

• r you
• u

Save ve money

• r g

r get et pa paid d to help t p the Gri rid

Batteries Similar to Generator

Source: alarmcentralsecurity.com Source: Sonnen

Other Applications of Storage

Peak demand reduction, grid support (mostly non-residential)

Time of use (arbitrage)

How Does Storage Work With Solar?

• On grid/off grid
• Solar charges batteries for later
• Grid can charge batteries too

(ac coupled)

• batteries “topped off”
• Batteries ‘kick in’ automatically

“Islanding” with grid connected

What Can Batteries Power?

Duri ring ng an outage ge

• Seamless backup power
• Critical loads Subpanel
• “Loads” consume power
• “Critical loads” consume

power- are vital to functioning”

• Essential lights, medical

equipment, well pump

Sizing a System: 2 Considerations

Power and Energy

Power: er:

• Instantaneous Watts (Measured in KW)
• What are you powering at any given instant
• Difference between 100 W light or 2,000 W

HVAC

• “Surge power”

Energy rgy:

• Quantity of power used/available over time
• Measured KWh
• Do you need to run load for 1 hour or 24

hours? (data center example)

Source: SimpliPhi

Terminology: Power and Energy

Energy (kWh) Power (Watts/KW)

The Johnsons lose power several times a year. Each time the power is

• ut for at least a day.

Batt ttery y Bank: nk: (P (Power wer 5 KW/ Ene nerg rgy y 6 KWh) )

• Fully re-charged by solar daily
• No solar = 1 day of backup power
• (days of autonomy)

Cri ritica ical Loads ds

• Refrigerator; small microwave
• Some lights; some outlets
• Cable modem

What they chose not

• t to po

power wer:

• Stove; dryer; electric water heater

Solar Battery Backup Example

.

How is storage priced?

Tot

• tal

al cost t = hardware costs + installation costs + lifetime maintenance costs

Hardware are (battery, , inver erter) er)

• Price per kW (power)

OR

• Price per kWh (energy)

(Charge Controler AC/DC coupling) Install stallation ation +

• Cost of design,

installation, and permitting

• Additional

equipment Lifetim time e maint intena enanc nce

• Battery replacement
• Associated labor cost

$$$ $$$ $$ $$ $

Federal Tax Credit for Storage

30% federal tax credit available for storage systems that are 100% charged by solar

• Value: 30%

% of the e total

• tal system

em co cost st (hardware + installation) for fully solar-charged batteries

• Storage systems that are at least

st 75% % charged by solar are eligible for a portion of the full tax credit

• Storage system that are less than

n 75% % charged by solar are ineligible for the tax credit

Common Battery Technologies

”Deep Cycle” Lead Acid/AGM

Pros:

• Lower upfront cost
• Tried and true

Cons:

• Maintenance requirement
• Slower energy discharge

(power)

• High space requirement
• Shorter lifespan
• Less usable energy per cycle

Lithium ium Ion

Pros:

• High energy density
• Lower lifetime costs
• Longer lifespan
• Small space requirement
• More usable energy per cycle

Cons:

• Higher upfront cost
• Newer to market
• Losses for heating/venting

Bu But w t wait, t, there’s more!

There are other chemistries used in battery applications, but their deployment is much uch le less common

• mmon

Operations and Maintenance

Space Requirements

Lithiu thium m Ion

• Single, larger box
• Wall-mounted or floor-mounted
• Can often also be wired together

Lead d Ac Acid

• Small, shoe box-sized battery
• Wired together in a group
• Can sit directly on floor or shelf
• Requires more space

Source: Fire Mountain Solar Source: Clean Technica

Operations and Maintenance

• Batteries function best in cont

ntro rolled lled envir ironm nments ents

• Specific conditions depends on chemistry:
• Lead-acid
• Stable temperatures (ideal: 50℉ – 80℉)
• No extreme heat or freezing air
• Often installed indoors (garage/basement)
• Special ventilation required for unsealed batteries
• Lithium Ion
• Wider temperature range (~32℉ - 100℉)
• Some can be installed outdoors in stable climates

Siting Considerations

Operations and Maintenance

• Installer’s labor should be warranted (wiring)
• Note: Solar panels are warranted for 25 years

Source: https://blog.pickmysolar.com/home-battery-backup-comparison-tesla-sonnenbatterie

Basic cost estimates (example)

Hardware are co cost st (examp amples les) ) + Installatio tallation n co costs sts + $3,000 - $5,000 for retrofit installation and additional equipment Maint intenan enance ce co costs ts Varies between installers and battery chemistries

Pri ricing ing for r our r small ll 6 kW kWh h batt ttery y example: xample: ~$6,000 + $4,000 + $1,000 = ~$11,000

Equipment Cost Size Powerwall 2 (Li-ion) $6,200 13.5 kWh Powerwall 1 (Li-ion) $3,000 6.4 kWh LG Chem (Li-ion) $6,000 6.6 kWh Sonnen Eco 4 (Li-ion) $10,000 4 kWh Sealed Lead Acid $5,200 12 kWh

Check out our Residential Storage Guide!

Installing Storage with Solar vs. Later

Lat ater

• Solar now and wait for battery

prices to fall further

• AC-coupled or retrofit existing

solar array

• Inverter replace or add
• Uncertain eligibility for solar

Federal Tax Credit With Solar ar

• Immediate backup power benefits
• May reduce some shared labor

and admin costs by paying a contractor once instead of twice

• Eligible for solar Federal Tax Credit

The value of resiliency

Losing power does have a cost

Latest update from the IRS

In Marc rch 2018, the IRS issued a private-letter ruling clarifying:

• Adding storage to an

existing rooftop solar array will qualify for the 30% Federal Tax Credit

• Solar charging

stipulations still apply