Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
Smart thermostat
Table title:
Internal Studies
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Fuel </th><th colspan=1 rowspan=1 > Sample Size </th><th colspan=1 rowspan=1 > Pre-Nest Total Energy Use </th><th colspan=1 rowspan=1 > Pre-Nest HVAC </th><th colspan=1 rowspan=1 > Total Energy Savings </th><th colspan=1 rowspan=1 > % of HVAC </th></tr>
<tr> <td colspan=1 rowspan=1 > Natural Gas (therms/yr) </td><td class="highlighted"  colspan=1 rowspan=1 > 735 </td><td colspan=1 rowspan=1 > 774 </td><td colspan=1 rowspan=1 > 584 </td><td colspan=1 rowspan=1 > 56 ±12 </td><td colspan=1 rowspan=1 > 9.6 ±2.1% </td></tr>
<tr> <td colspan=1 rowspan=1 > Electricity (kWh/yr) </td><td class="highlighted"  colspan=1 rowspan=1 > 624 </td><td colspan=1 rowspan=1 > 12,355 </td><td colspan=1 rowspan=1 > 3,351 </td><td colspan=1 rowspan=1 > 585 ±97 </td><td colspan=1 rowspan=1 > 17.5 ±2.9% </td></tr>
</table>
Question:
What was the sample size of homes for Smart Thermostat fuel usage analysis?
Answer:
The study had a sample size of 735 homes for natural gas usage analysis and 624 homes for electrical analysis.