An Experimental Analysis of the Impact of Tree Shade on Electricity Consumption

Article Figures & Data

Table 1.

Comparison of Light Conditions (PAR) and Electricity Used for Cooling (kWh) Between Apollo and Hades.

Time Period	Mean PAR		t-statistic	kWh/day		t-statistic
Time Period	Apollo	Hades	t-statistic	Apollo	Hades	t-statistic
April	609.24	153.07	12.12^{^z}	1.33	0.28	7.86^{^z}
May	655.18	57.05	18.75^{^z}	2.56	0.65	7.87^{^z}
June	684.71	50.11	22.92^{^z}	4.71	1.93	10.69^{^z}
July	650.96	41.55	29.06^{^z}	4.40	1.80	15.18^{^z}
August	543.44	50.12	14.89^{^z}	3.61	1.47	8.15^{^z}
September 1–17	506.87	47.89	14.07^{^z}	3.33	1.45	6.59^{^z}

Table 2.

OLS regression estimation of factors affecting electricity used for cooling. Dependent variable: kWh/day.

Explanatory Variable	(expected sign)	Coefficient Estimate (Std. Error)	Coefficient Estimate (Std. Error)
Mean daily PAR^{^z}	(+)	0.0028^{^y}
Mean daily PAR^{^z}	(+)	(0.0002)
Mean daily high temperature^{^x}	(+)	0.0191^{^y}
Mean daily high temperature^{^x}	(+)	(0.0015)
Maximum daily high PAR^{^w}	(+)		0.0008^{^y}
Maximum daily high PAR^{^w}	(+)		(0.0001)
Maximum daily high temperature^{^v}	(+)		0.0166^{^y}
Maximum daily high temperature^{^v}	(+)		(0.0020)
R²	0.8014	0.7566
F (model)	631.40	486.35
N	316.00	316.00

↵^zDaily PAR readings averaged across readings taken at 15-minute intervals, non-nighttime (PAR > 0).
↵^ycoefficient statistically significant at 0.01 level.
↵^xDaily temperature averaged across readings taken at 15-minute intervals, nonnighttime (PAR > 0).
↵^wThe highest PAR value each day.
↵^vThe highest temperature each day.

	kWh/day	mean PAR	max inside temp	Apollo (sun) min inside temp	max outside temp	min outside temp	N
April	1.33	609.24	78.55	52.24	77.22	50.72	30
April	(0.87)	(188.97)	(5.28)	(8.26)	(7.84)	(8.15)
May	2.56	655.18	82.00	58.92	83.68	57.77	28
May	(1.17)	(163.89)	(3.89)	(5.99)	(4.19)	(5.69)
June	4.71	684.71	86.14	67.58	92.46	65.95	27
June	(0.90)	(142.94)	(4.29)	(2.94)	(3.27)	(2.94)
July	4.40	650.96	83.27	69.01	93.39	67.72	28
July	(0.79)	(110.50)	(2.18)	(3.07)	(2.48)	(3.47)
August	3.61	543.44	81.51	69.41	89.24	68.72	29
August	(1.29)	(176.51)	(3.63)	(2.71)	(5.73)	(3.33)
September 1-17	3.33	506.87	80.16	65.59	87.98	68.42	17
September 1-17	(1.04)	(133.29)	(2.34)	(4.92)	(4.92)	(3.97)
April – September 17	3.26	614.55	82.06	63.93	87.14	62.72	159
April – September 17	(1.58)	(316.64)	(4.52)	(8.38)	(7.70)	(8.56)

	kWh/day	mean PAR	max inside temp	Hades (shade) min inside temp	max outside temp	min outside temp	N
April	0.28	153.07	73.64	54.15	75.10	52.08	29
April	(0.42)	(74.23)	(4.34)	(7.55)	(7.35)	(7.61)
May	0.65	57.05	76.07	60.36	80.28	58.93	27
May	(0.48)	(25.15)	(1.74)	(5.64)	(4.08)	(5.67)
June	1.93	50.11	78.79	69.31	88.60	66.99	27
June	(1.01)	(17.15)	(1.20)	(2.54)	(2.65)	(2.66)
July	1.80	41.55	78.51	70.04	n/a	n/a	28
July	(0.58)	(10.38)	(0.83)	(2.77)
August	1.47	50.12	76.92	70.52	n/a	n/a	29
August	(0.58)	(25.73)	(1.77)	(2.60)
September 1-17	1.45	47.89	75.68	66.84	n/a	n/a	17
September 1-17	(0.55)	(17.82)	(1.76)	(4.46)
April – September 17	1.25	47.89	76.78	64.94	n/a	n/a	157
April – September 17	(0.88)	(58.48)	(2.87)	(9.09)