Building to be Off Grid at Latitude 17.5

Single-Family Residence - September 2018

Building to be independent of an unreliable grid.

Quick Facts

Average Annual Savings

$3,000

Energy Needs Met

100%

or more of electricity

Net Investment

$21,581

Return on Investment

13.9%

Property

Owner:: Brian Boschen
Type:: Single-Family Residence
Address:: St. Croix, VI 00820
Size:: 1,670 sq ft
Energy need met:: 100% or more of electricity
Designations:: Passive house; Zero net energy

Technology

Type:: Solar PV
Installed:: September 2018
Size of System:: 7.2 kW
Purposes:: To generate electricity

Financial Details

Gross Cost of System:: $30,850
Value of Tax Credits:: $9,249
Net Cost of System:: $21,581
Annual Savings:: $3,000
Own or Lease:: Purchase with Loan
Additional Financial Notes:: Financed as part of house construction. Further savings anticipated by installing an electric car charging station and reducing gasoline costs by $120 per month.

Professionals & Suppliers

Products:: Tesla
Installers:: ProSolar Systems, LLC (St. Thomas)

What You Need to Know

Description:

24 x Trina TSM-300W panels 2 x Tesla Powerwall 2.0 Tesla Powerwall: Energy Gateway

Other Benefits:

Independence from fragile grid which fails weekly, and which was down for 3+ months after last years hurricanes. Powering Air Conditioning! Providing charging for an electric car, saving gas even with the use of A/C! Web monitoring of power generation and usage via smartphone app

Maintenance Requirements:

Performance monitored by supplier

Efficiency or Sustainability Improvements:

Quad-Lock Insulated Concrete Forms (ICF) construction provides 2" of foam insullation inside and out on 6" poured concrete exterior walls, and 7" of steel reinforced foam insulation under the poured concrete roof. Heat pump water heater, high efficiency mini-split air conditioning in bedrooms. Intelaflo multispeed high efficiency pool pump. Glass blocks for ambient lighting. LED lights throughout. Energy Star appliances. High efficiency ceiling fans.

My Motivation:

We were without power for over 3 months following hurricanes Irma and Maria. Since water is pumped from cisterns, we were also without water. Aside from that, the utility regularly has outages on a weekly basis, and locally gas generated costs are very high, ranging from $0.45-0.60/kWh. We wanted to be free to use air conditioning when needed, power our swimming pool pump daily, and drive without concern for fuel economy.

Advice:

We initially specified low cost FLA batteries for storage, recognizing that storage costs are coming down. However, we didn't anticipate that they were coming down as quickly as they did, and we switched to Tesla PowerWall 2.0 before installation - at a lower cost!

Experience with Installer:

We leveraged the local experience of other friends who had already installed net-metered or grid-tied systems and their experience with local installers, and decided to go with a well known major local installer.

Additional Notes:

We were originally going to do net-metering. The day we went to sign the contract, the local utility reached their net-metering capacity cap, preventing us from signing up! Meanwhile, we had friends who had recently installed net-metered systems, and when the grid went down for 3 months due to hurricane damage, our friends with net-metering were without power unless they ran their generator. That sealed our decision to go completely off-grid!

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