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News from Prairie Hill

Dear Friends,

Winter is upon us and soon we will wake to the shortest day of the year. We look forward to the cycle of the sun's gradual return. In the meantime, we are finding ways to light up the darkness with fun and good cheer. May your home, too, be filled with light and love.

Upcoming events at Prairie Hill

Please take a few minutes to mark these Prairie Hill Zoom events on your new 2022 calendar. We look forward to seeing you soon!

Info Meeting
Wednesday, January 12
6:00-7:00 p.m.

Find out about cohousing. How does it work? Do you have your own kitchen? How is it different from owning a condo? What it's like to have someone else cook dinner for you once a week? To get the link text Val Bowman at 916-751-9188.

Meet and Greet
Saturday, January 29
10:00-11:30 a.m.

Grab a cup of coffee and join us for this casual event. Meet people who live at Prairie Hill as well as others who are interested in learning more about it. To get the link to this Zoom event, send a text to Val Bowman at 916-751-9188 or write to us at

CELEBRATING IN THE TIME OF COVID: Bob Reynolds masked up and donned his seasonal best to start Prairie Hill's holiday festivities off right!
GINGERBREAD HOUSE AND GARDEN BUILDING: Everyone cast their ballots for the winners in the graham cracker gingerbread challenge.
HOMEBAKED COOKIE TRADING: These almond pinwheels were a popular choice in the cookie exchange.
BUILD IT STURDY, BUILD IT TALL: Teams of masked builders were given toothpicks and gum drops. They had five minutes to build the tallest structure.
Competition was intense!
Here's the winner!
BUILDING SOIL: We arranged with the city to dump five truckloads (!) of leaves at Prairie Hill. Crews like the one above delivered wheelbarrow loads to gardens all over the site. We are going to have some of the richest soil in the county!
SUN POWERED: Prairie Hill homes are sited to take advantage of the sun to generate power. There are currently ten units with solar panels installed.

A report on solar energy at Prairie Hill

John McGonegle gives a detailed report of how solar panels are working at Prairie Hill

As of December, 2021, there are ten Prairie Hill units with photovoltaic (PV) systems installed for a total capacity of 33 kilowatts. The PV systems range from 5 to 12 roof-mounted panels. The systems are tied to the electrical grid and net metered. If the PV system is producing more energy than the unit is using, the excess energy is delivered to the utility grid and banked to the user’s account. The roof area on the four-unit stacked flat is divided to allow each owner to purchase their own PV system. Some of the PV systems have power optimizers with string inverters and some have micro-inverters.

How it works

For example, in 2020, one of our 3.8 kilowatt (kWh) PV systems produced 5,247 kWh and the unit’s usage was 4,546 kWh. The surplus 1304 kWh was credited to the user’s account. This 3.8 kW PV system has generated over 10,000 kWh since its commissioning in February, 2019. That's the equivalent of 126 trees saved and 16,755 lbs. of CO2 not released into the atmosphere.

The PV systems shut down when the normal power is lost, so they do not provide emergency power. Systems with batteries and transfer switches can be designed to interface to the utility and provide emergency power from the batteries when the normal power is lost, but these systems are very expensive.

Costs are going down and panels are improving

The cost of basic solar systems has been decreasing at the same time that power density and the efficiency of PV panels have been improving. This means even units with small roof areas can produce more energy. In the last three years, the standard panel has changed from 345 watts to 420 watts, a 23% increase in power density and 11% improvement in efficiency.

Prairie Hill Net Zero Energy Building

Our Prairie Hill cohousing units are equipped with high efficiency systems. We have managed to achieve our goal of building sustainable homes with a low carbon footprint. With solar photovoltaic panels installed, the units can be near net zero energy (NNZE) or net zero energy building (NZEB). A net zero energy building produces enough renewable energy to meet its own annual energy consumption requirements, thereby reducing the use of nonrenewable energy in the building sector.

Details from John McGonegle's usage logs

It's interesting to track your energy usage. In 2020, my 1290-square-foot 2-story duplex had a Net Zero Energy Building (NZEB) usage year. I used 4,546 kWh for heating, cooling, lighting, ventilation, water heating and plug loads during the twelve-month period. The Energy Usage Intensity (EUI) for the 12 month period was 12.88 kBTU/ square foot. The offsite energy purchased was 9.59 kBTU/ square foot. This compares to a US mean residential multi-family housing site usage of 59.6 kBTU/ square foot. The energy production from the 3.795 kW photovoltaic system was 5.247 megaWatts during the year. The photovoltaic system produced 115% of the electrical needs for the unit.

Low energy bills

My total MidAmerican Energy annual bill for 2020 was $136.31 with only February and March bills exceeding the $8.59 monthly meter charge. The water bill for 2020 of $243.64 exceeded the electric bill. The 2020 surplus energy (1304 kWH) may offset the 2021 winter usage, and I would have 12 months of minimum payments of $8.59! The 4.546 megaWatts electrical usage would have cost approximately $558, so the estimated saving is $422.

The PV system production displaced 7,047 lbs. of CO2 and is equivalent to 53 trees planted in 2020. The purchased electricity gives the unit an equivalent carbon footprint of 0 lbs. of C02, compared to a 5,455 lbs. average for a one-person household per year. 

As 2021 draws to an end, we send warm holiday cheer your way. We hope to see you soon!
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Iowa City Cohousing · 140 Prairie Hill Ln · Iowa City, IA 52246-2029 · USA

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