Page 50 - Zero Net Energy Case Study Homes-Volume 1

CASE STUDY NO. 2
FORTUNATO HOUSE RENOVATION
Energy Performance
Post-Occupancy Measurement
Energy Use—Monitoring and Measurement
In 2016, the owners arranged for meters to be installed to record separately the energy use and the energy production by the solar PV system. A full year of data was recorded for the period 4/2016-3/2017. The house plus two electric vehicles (EVs) used 10,466 kWh in that period, which was confirmed by SCE’s net meter total. A reasonable estimate of the annual electric energy used to charge the EVs was done based on recorded miles driven for this period and a “mileage” rate of 3 miles per kWh. This estimate was 3,118 kWh, which gives a (non-metered) total energy use for the house alone of 7,350 kWh. This translates to an EUI of 11.7 kBtu/sq.ft.
The total energy use by month (house plus cars) is given in the performance chart below. The data includes monthly energy use to charge two electric vehicles since this category of energy use was not separately metered or estimated.
Energy Production versus Energy Use: Zero Net Energy Performance
The charts on the opposite page show the relative solar PV system performance over the course of that one year, (4/2016-3/2017). The chart of solar production compared to metered energy use of house plus cars shows the balance between the excess energy use in the winter months with the excess energy production in the summer.
The precise balance is indicated in the chart giving the cumulative net energy production. This
chart shows the progression of the energy performance toward ZNE by adding each month’s net
energy performance to the previous month’s total. If, at the end of the year, the curve remains
on the positive side of the zero axis, then the building is indeed performing at ZNE. For this case
study house plus the two EVs, the curve essentially reaches precisely the “net zero” mark at the
UI
Measured Energy Use (2016 - 2017)
7,350 kWh/year Measured EUI* = 11.7
*house only—deducts estimat- ed annual energy use for charg- ing EVs from metered total.
Measured Monthly Energy Use
38
Zero Net Energy Case Study Homes: Volume 1
end of one year, a near perfect outcome showing a match of design, operation and weather.
(2016 - 2017)
3.00 2.50 2.00 1.50 1.00 0.50 0.00
Energy Use (All Electric)
Apr
2016
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan Feb Mar
2017
kBtu/sq.ft.
E