Solar heating performance


Yes, we do use Solar heating here at home! We have two low-profile solar collectors mounted on a south facing wall.
They are controlled by an Okapi 2 Bluetooth system and all heating data is logged on an Android tablet.

We even let the heaters run all summer (2015), so we could capture the data.
There are uses for solar heat in the summer months, for example to help dry out a basement, dry clothes or food, or to simply provide warmth on a chilly day.


Data logging began in January 2015, when the Okapi Solar Calculator app was in development and being tested.

Totals for February 2015 to January 2016 inclusive:

Totals Heater 1 Heater 2 Both
kWh kWh kWh BTU
February 73.2 66.2 139.3 475458.1
March 81.5 78.9 160.4 547471.3
April 80.0 62.1 142.1 484913.1
May 78.1 57.5 135.6 462597.7
June 57.7 40.6 98.4 335608.0
July 77.1 84.7 161.7 551838.8
August 131.3 138.0 269.3 918862.4
September 139.4 149.3 288.7 985026.8
October 98.0 103.0 201.1 686034.0
November 51.4 48.4 99.8 340645.0
December 42.8 52.1 94.9 323853.0
January 61.2 79.7 141.0 480959.0
Annual totals 971.8 960.5 1,932.3 6,593,267.2

*From December 2015, the temperature sensor in Heater 2 appears to have dropped closer to the motor in the fan, the temperatures recorded may be at least 5% higher than actual


Monthly reports:


Heater 1 Heater 2
February 2015 February 2015
1-Feb-15 289 w 1-Feb-15 215 w
2-Feb-15 699 w 2-Feb-15 886 w
3-Feb-15 3158 w 3-Feb-15 2104 w
4-Feb-15 5596 w 4-Feb-15 5322 w
6-Feb-15 2895 w 6-Feb-15 2386 w
7-Feb-15 2750 w 7-Feb-15 2755 w
8-Feb-15 4989 w 8-Feb-15 4627 w
9-Feb-15 893 w 9-Feb-15 769 w
11-Feb-15 606 w 11-Feb-15 782 w
12-Feb-15 8695 w 12-Feb-15 7765 w
14-Feb-15 7033 w 14-Feb-15 6225 w
17-Feb-15 6261 w 17-Feb-15 6193 w
19-Feb-15 33 w 19-Feb-15 29 w
20-Feb-15 2963 w 20-Feb-15 3096 w
21-Feb-15 6826 w 21-Feb-15 5958 w
23-Feb-15 128 w 23-Feb-15 109 w
24-Feb-15 5691 w 24-Feb-15 5095 w
26-Feb-15 1246 w 26-Feb-15 1241 w
27-Feb-15 5064 w 27-Feb-15 4039 w
28-Feb-15 7355 w 28-Feb-15 6577 w
Total 73170 w Total 66173 w
73.17 kWh 66.173 kWh
249666.4 BTU 225791.6 BTU
Heater 1 Heater 2
March 2015 March 2015
1-Mar-15 5245 w 1-Mar-15 5312 w
3-Mar-15 5195 w 3-Mar-15 4927 w
4-Mar-15 52 w 4-Mar-15 170 w
6-Mar-15 7157 w 6-Mar-15 6729 w
7-Mar-15 2060 w 7-Mar-15 1815 w
8-Mar-15 4813 w 8-Mar-15 4640 w
9-Mar-15 2841 w 9-Mar-15 2915 w
10-Mar-15 5375 w 10-Mar-15 5119 w
11-Mar-15 434 w 11-Mar-15 190 w
12-Mar-15 224 w 12-Mar-15 318 w
13-Mar-15 2993 w 13-Mar-15 2038 w
14-Mar-15 7515 w 14-Mar-15 6798 w
17-Mar-15 1692 w 17-Mar-15 2673 w
20-Mar-15 5786 w 19-Mar-15 161 w
21-Mar-15 1765 w 20-Mar-15 6448 w
23-Mar-15 1438 w 21-Mar-15 2221 w
24-Mar-15 6544 w 22-Mar-15 28 w
25-Mar-15 7179 w 23-Mar-15 1917 w
26-Mar-15 372 w 24-Mar-15 6207 w
29-Mar-15 8032 w 25-Mar-15 6123 w
30-Mar-15 4462 w 26-Mar-15 287 w
31-Mar-15 333 w 29-Mar-15 7541 w
30-Mar-15 4066 w
31-Mar-15 298 w
Total 81507 w Total 78941 w
81.507 kWh 78.941 kWh
278113.4 BTU 269357.9 BTU
Heater 1 Heater 2
April 2015 April 2015
1-Apr-15 6298 w 1-Apr-15 5904 w
2-Apr-15 6335 w 2-Apr-15 4418 w
3-Apr-15 1156 w 3-Apr-15 1009 w
4-Apr-15 24 w 5-Apr-15 4036 w
5-Apr-15 5649 w 6-Apr-15 3827 w
6-Apr-15 5260 w 7-Apr-15 130 w
7-Apr-15 139 w 8-Apr-15 4600 w
8-Apr-15 6112 w 9-Apr-15 4632 w
9-Apr-15 6295 w 11-Apr-15 2547 w
11-Apr-15 3474 w 12-Apr-15 2396 w
12-Apr-15 2805 w 13-Apr-15 4766 w
13-Apr-15 6189 w 15-Apr-15 3735 w
14-Apr-15 34 w 16-Apr-15 3977 w
15-Apr-15 4882 w 17-Apr-15 657 w
16-Apr-15 4687 w 18-Apr-15 3868 w
17-Apr-15 862 w 19-Apr-15 3827 w
18-Apr-15 4967 w 20-Apr-15 4104 w
19-Apr-15 4757 w 21-Apr-15 713 w
20-Apr-15 5445 w 23-Apr-15 885 w
21-Apr-15 804 w 24-Apr-15 1343 w
23-Apr-15 1202 w 25-Apr-15 499 w
24-Apr-15 1792 w 26-Apr-15 145 w
25-Apr-15 595 w 27-Apr-15 76 w
26-Apr-15 155 w
27-Apr-15 102 w
Total 80020 w Total 62094 w
80.02 kWh 62.094 kWh
273039.6 BTU 211873.5 BTU
Heater 1 Heater 2
May 2015 May 2015
1-May-15 1668 w 1-May-15 1406 w
3-May-15 5024 w 3-May-15 3474 w
4-May-15 5709 w 4-May-15 3852 w
5-May-15 4305 w 5-May-15 3121 w
6-May-15 4004 w 6-May-15 3020 w
7-May-15 3947 w 7-May-15 3146 w
8-May-15 3556 w 8-May-15 2755 w
10-May-15 1123 w 10-May-15 802 w
11-May-15 2327 w 11-May-15 1797 w
12-May-15 299 w 14-May-15 1728 w
14-May-15 1898 w 15-May-15 3544 w
15-May-15 4792 w 16-May-15 3080 w
16-May-15 4511 w 17-May-15 433 w
17-May-15 522 w 18-May-15 3242 w
18-May-15 4562 w 19-May-15 3101 w
19-May-15 4164 w 20-May-15 535 w
20-May-15 674 w 21-May-15 2605 w
21-May-15 3450 w 23-May-15 417 w
23-May-15 531 w 24-May-15 1992 w
24-May-15 2736 w 25-May-15 3046 w
25-May-15 4136 w 27-May-15 3324 w
27-May-15 4651 w 28-May-15 1486 w
28-May-15 2024 w 29-May-15 2872 w
29-May-15 3881 w 30-May-15 2646 w
30-May-15 3610 w 31-May-15 46 w
31-May-15 54 w
Total 78104 w Total 57470 w
78.104 kWh 57.47 kWh
266501.9 BTU 196095.8 BTU
Heater 1 Heater 2
June 2015 June 2015
3-Jun-15 178 w 3-Jun-15 96 w
4-Jun-15 3898 w 4-Jun-15 2817 w
5-Jun-15 3758 w 5-Jun-15 2696 w
7-Jun-15 101 w 7-Jun-15 131 w
8-Jun-15 2442 w 8-Jun-15 1691 w
9-Jun-15 2780 w 9-Jun-15 2004 w
10-Jun-15 413 w 10-Jun-15 344 w
11-Jun-15 2544 w 11-Jun-15 1908 w
12-Jun-15 2655 w 12-Jun-15 1647 w
13-Jun-15 2087 w 13-Jun-15 1450 w
14-Jun-15 1326 w 14-Jun-15 1008 w
15-Jun-15 3650 w 15-Jun-15 2677 w
16-Jun-15 319 w 16-Jun-15 220 w
17-Jun-15 3702 w 17-Jun-15 2595 w
18-Jun-15 3997 w 18-Jun-15 2849 w
20-Jun-15 3774 w 20-Jun-15 2680 w
21-Jun-15 302 w 21-Jun-15 89 w
23-Jun-15 2338 w 23-Jun-15 1810 w
24-Jun-15 1479 w 24-Jun-15 889 w
25-Jun-15 3155 w 25-Jun-15 2278 w
26-Jun-15 3082 w 26-Jun-15 2139 w
27-Jun-15 3545 w 27-Jun-15 2423 w
28-Jun-15 1124 w 28-Jun-15 777 w
29-Jun-15 1949 w 29-Jun-15 1358 w
30-Jun-15 3147 w 30-Jun-15 2036 w
Total 57745 w Total 40612 w
57.745 kWh 40.612 kWh
197034.1 BTU 138573.9 BTU
Heater 1 Heater 2
July 2015 July 2015
1-Jul-15 3783 w 1-Jul-15 2567 w
2-Jul-15 4025 w 2-Jul-15 2824 w
3-Jul-15 3659 w 3-Jul-15 2323 w
4-Jul-15 4697 w 4-Jul-15 3099 w
5-Jul-15 2009 w 5-Jul-15 1526 w
6-Jul-15 4604 w 6-Jul-15 6434 w
7-Jul-15 4095 w 7-Jul-15 5230 w
8-Jul-15 2072 w 8-Jul-15 2629 w
9-Jul-15 4360 w 9-Jul-15 6210 w
10-Jul-15 3948 w 10-Jul-15 5046 w
11-Jul-15 5061 w 11-Jul-15 6917 w
12-Jul-15 3218 w 12-Jul-15 4215 w
13-Jul-15 4928 w 13-Jul-15 6554 w
14-Jul-15 4947 w 14-Jul-15 6801 w
15-Jul-15 3456 w 15-Jul-15 4592 w
16-Jul-15 4871 w 16-Jul-15 5007 w
17-Jul-15 5190 w 17-Jul-15 4972 w
18-Jul-15 1893 w 18-Jul-15 1915 w
21-Jul-15 463 w 21-Jul-15 420 w
22-Jul-15 100 w 22-Jul-15 96 w
23-Jul-15 1889 w 23-Jul-15 1864 w
24-Jul-15 1257 w 24-Jul-15 1058 w
25-Jul-15 620 w 25-Jul-15 518 w
26-Jul-15 1629 w 26-Jul-15 1636 w
27-Jul-15 283 w 27-Jul-15 218 w
28-Jul-15 213 w 28-Jul-15 226 w
29-Jul-15 3670 w 29-Jul-15 3814 w
30-Jul-15 6200 w 30-Jul-15 6138 w
31-Jul-15 4023 w 31-Jul-15 3669 w
Total 77057 w Total 84671 w
77.057 kWh 84.671 kWh
262929.4 BTU 288909.4 BTU
Heater 1 Heater 2
August 2015 August 2015
1-Aug-15 7201 w 1-Aug-15 7333 w
2-Aug-15 6678 w 2-Aug-15 6655 w
3-Aug-15 6869 w 3-Aug-15 7365 w
4-Aug-15 5994 w 4-Aug-15 6597 w
5-Aug-15 3756 w 5-Aug-15 4198 w
6-Aug-15 6165 w 6-Aug-15 6520 w
7-Aug-15 3520 w 7-Aug-15 3913 w
8-Aug-15 3156 w 8-Aug-15 3303 w
10-Aug-15 1997 w 10-Aug-15 1975 w
11-Aug-15 6659 w 11-Aug-15 6956 w
12-Aug-15 758 w 12-Aug-15 662 w
13-Aug-15 4371 w 13-Aug-15 4653 w
14-Aug-15 7089 w 14-Aug-15 7132 w
15-Aug-15 4626 w 15-Aug-15 5069 w
16-Aug-15 7239 w 16-Aug-15 7622 w
17-Aug-15 7491 w 17-Aug-15 7892 w
18-Aug-15 7641 w 18-Aug-15 6085 w
19-Aug-15 6632 w 19-Aug-15 6956 w
20-Aug-15 6819 w 20-Aug-15 7096 w
21-Aug-15 6053 w 21-Aug-15 6411 w
22-Aug-15 2762 w 22-Aug-15 2941 w
23-Aug-15 1533 w 23-Aug-15 1648 w
24-Aug-15 1225 w 24-Aug-15 3697 w
28-Aug-15 8380 w 28-Aug-15 8518 w
29-Aug-15 6665 w 29-Aug-15 6816 w
30-Aug-15 6300 w 30-Aug-15 6261 w
31-Aug-15 7898 w 31-Aug-15 8147 w
Total 131279 w Total 138013 w
131.279 kWh 138.013 kWh
447942.5 BTU 470919.9 BTU
Heater 1 Heater 2
September 2015 September 2015
1-Sep-15 510 w 1-Sep-15 622 w
2-Sep-15 6180 w 2-Sep-15 6455 w
3-Sep-15 7094 w 3-Sep-15 7238 w
4-Sep-15 4425 w 4-Sep-15 4984 w
5-Sep-15 6259 w 5-Sep-15 6827 w
6-Sep-15 8667 w 6-Sep-15 9700 w
7-Sep-15 8389 w 7-Sep-15 8891 w
9-Sep-15 1689 w 9-Sep-15 1934 w
10-Sep-15 156 w 10-Sep-15 170 w
11-Sep-15 119 w 11-Sep-15 83 w
12-Sep-15 62 w 12-Sep-15 137 w
14-Sep-15 1744 w 14-Sep-15 1741 w
15-Sep-15 331 w 15-Sep-15 467 w
16-Sep-15 3377 w 16-Sep-15 3600 w
17-Sep-15 9394 w 17-Sep-15 9533 w
18-Sep-15 8574 w 18-Sep-15 9037 w
19-Sep-15 9350 w 19-Sep-15 10208 w
20-Sep-15 5216 w 20-Sep-15 5694 w
21-Sep-15 8397 w 21-Sep-15 9150 w
22-Sep-15 6746 w 22-Sep-15 7260 w
23-Sep-15 9916 w 23-Sep-15 10877 w
24-Sep-15 7774 w 24-Sep-15 8408 w
25-Sep-15 9289 w 25-Sep-15 10040 w
26-Sep-15 7329 w 26-Sep-15 7453 w
27-Sep-15 8430 w 27-Sep-15 8756 w
28-Sep-15 8774 w 28-Sep-15 9186 w
29-Sep-15 3250 w 29-Sep-15 3092 w
30-Sep-15 2082 w 30-Sep-15 2257 w
Total 139417.5 w Total 149265.4 w
139.4175 kWh 149.2654 kWh
475712.2 BTU 509314.6 BTU
Heater 1 Heater 2
October 2015 October 2015
4-Oct-15 8826 w 4-Oct-15 8411 w
5-Oct-15 9297 w 5-Oct-15 9183 w
6-Oct-15 2051 w 6-Oct-15 2403 w
7-Oct-15 7605 w 7-Oct-15 7573 w
8-Oct-15 7315 w 8-Oct-15 7168 w
9-Oct-15 3108 w 9-Oct-15 3565 w
10-Oct-15 3984 w 10-Oct-15 3558 w
12-Oct-15 544 w 12-Oct-15 494 w
13-Oct-15 177 w 13-Oct-15 273 w
14-Oct-15 6446 w 14-Oct-15 6111 w
15-Oct-15 5178 w 15-Oct-15 5157 w
16-Oct-15 3885 w 16-Oct-15 4586 w
17-Oct-15 342 w 17-Oct-15 44 w
18-Oct-15 1406 w 18-Oct-15 1336 w
19-Oct-15 4308 w 19-Oct-15 5348 w
20-Oct-15 203 w 20-Oct-15 188 w
21-Oct-15 7406 w 21-Oct-15 8985 w
22-Oct-15 61 w 22-Oct-15 58 w
23-Oct-15 1359 w 23-Oct-15 1807 w
26-Oct-15 57 w 26-Oct-15 74 w
27-Oct-15 8733 w 27-Oct-15 9166 w
28-Oct-15 8838 w 28-Oct-15 9503 w
31-Oct-15 6916 w 31-Oct-15 8025 w
Total 98040.77 w Total 103015.9 w
98.04077 kWh 103.0159 kWh
334529 BTU 351505 BTU

Heater 1 Heater 2
November 2015 November 2015
11/4/2015 5 w 11/10/2015 10078 w
11/7/2015 2568 w 11/11/2015 1015 w
11/8/2015 3851 w 11/12/2015 8436 w
11/9/2015 6999 w 11/14/2015 1134 w
11/10/2015 7896 w 11/16/2015 1831 w
11/11/2015 523 w 11/17/2015 295 w
11/12/2015 7471 w 11/19/2015 2896 w
11/14/2015 929 w 11/25/2015 7688 w
11/16/2015 904 w 11/26/2015 7367 w
11/17/2015 97 w 11/27/2015 7520 w
11/19/2015 2137 w 11/29/2015 163 w
11/25/2015 6234 w
11/26/2015 5972 w
11/27/2015 5714 w
11/29/2015 112 w
Total 51412 w Total 48421 w
51.41199 kWh 48.4212 kWh
175425 BTU 165220 BTU
From December 2015, the temperature sensor in Heater 2 appears to have dropped closer to the barrel of the fan, the temperatures recorded may be at least 5% higher than actual

Heater 1 Heater 2
December 2015 December 2015
12/1/2015 6602 w 12/1/2015 7607 w
12/6/2015 4868 w 12/6/2015 5448 w
12/7/2015 6889 w 12/7/2015 7926 w
12/8/2015 1029 w 12/8/2015 1597 w
12/9/2015 65 w 12/9/2015 71 w
12/12/2015 134 w 12/12/2015 350 w
12/13/2015 5038 w 12/13/2015 6352 w
12/16/2015 481 w 12/16/2015 634 w
12/17/2015 614 w 12/17/2015 746 w
12/19/2015 1936 w 12/19/2015 1964 w
12/20/2015 1446 w 12/20/2015 2326 w
12/25/2015 6722 w 12/25/2015 8039 w
12/26/2015 6974 w 12/26/2015 8994 w
12/28/2015 23 w 12/28/2015 39 w
Total 42821 w Total 52091 w
42.82061 kWh 52.09133 kWh
146110 BTU 177743 BTU


Heater 1 Heater 2
January 2016 January 2016
1/2/2016 5861 w 1/2/2016 7355 w
1/4/2016 0 w 1/4/2016 4 w
1/6/2016 6278 w 1/6/2016 8196 w
1/7/2016 5756 w 1/7/2016 7880 w
1/9/2016 348 w 1/9/2016 421 w
1/10/2016 2585 w 1/10/2016 3740 w
1/11/2016 2847 w 1/11/2016 3047 w
1/12/2016 5179 w 1/12/2016 7192 w
1/13/2016 2252 w 1/13/2016 2619 w
1/14/2016 1806 w 1/14/2016 2197 w
1/15/2016 6494 w 1/15/2016 8338 w
1/20/2016 4468 w 1/20/2016 6233 w
1/22/2016 6716 w 1/22/2016 8847 w
1/24/2016 12 w 1/23/2016 22 w
1/25/2016 1537 w 1/24/2016 13 w
1/26/2016 1326 w 1/25/2016 1907 w
1/28/2016 7763 w 1/26/2016 1559 w
1/28/2016 10156 w
Total 61229 w Total 79726 w
61.22899 kWh 79.72617 kWh
208922 BTU 272037 BTU