Query Vars

functions.php

<?php
 function custom_query_vars_filter($vars) {
  $vars[] .= 'bedrooms';

  return $vars;
}
add_filter( 'query_vars', 'custom_query_vars_filter' );

Loop

<?php $bedrooms = get_query_var('bedrooms'); 

$args = array(
	'posts_per_page' => -1,
	'post_type' => 'property',
	'orderby' => 'title',
	'order' => 'DESC',
);

if ($bedrooms >= "1" ) {
	$args['meta_query'] = array(
		// 		'relation'		=> 'AND',
				array(
					'key'	 	=> '_bedrooms',
					'value'	  	=> $bedrooms,
					'compare' 	=> '=',
				)
		);	
} 

Or

<?php
// functions.php
function custom_query_vars_filter($vars) {
    $vars[] .= 'ecs01';
    $vars[] .= 'ecs02';
    $vars[] .= 'ecs03';
    $vars[] .= 'ecs04';
    $vars[] .= 'ecs05';
    $vars[] .= 'ecs06';

  return $vars;
}
add_filter( 'query_vars', 'custom_query_vars_filter' );

// loop
$ecs01 = sanitize_text_field(get_query_var('ecs01'));
$ecs02 = sanitize_text_field(get_query_var('ecs02'));
$ecs03 = sanitize_text_field(get_query_var('ecs03'));
$ecs04 = sanitize_text_field(get_query_var('ecs04'));
$ecs05 = sanitize_text_field(get_query_var('ecs05'));
$ecs06 = sanitize_text_field(get_query_var('ecs06'));

if (! empty($ecs01) || ! empty($ecs02) || ! empty($ecs03) || ! empty($ecs04) || ! empty($ecs05) || ! empty($ecs06) ) { 
	$ecs = array($ecs01, $ecs02, $ecs03, $ecs04, $ecs05, $ecs06); 
};
$args = array(
	'post_type' => 'electric-locations',
	'posts_per_page' => -1,
	'post_status' => 'publish',
);
if (! empty($ecs) ) { 
	$args['tax_query'] = array(
		array (
            'taxonomy' => 'electric-locations-category',
            'field' => 'slug',
            'terms' => $ecs,
        )
	);
}

?>
<?php $the_query = new WP_Query( $args ); ?>
// ... loop

To output the URL with the var string use a confirmation page in gravity forms and pass the variable, something likie this

ecs01={Categories (Company):1.1}&ecs02={Categories (Development Opportunities):1.2}&ecs03={Categories (Gigaplant):1.3}&ecs04={Categories (Innovation Hub):1.4}&ecs05={Categories (Networks):1.5}&ecs06={Categories (University and Colleges):1.6}

Or use your own form element like this:

<script language="JavaScript">
function toggle(source) {
    var checkboxes = document.querySelectorAll('#cat-form input[type="checkbox"]');
    for (var i = 0; i < checkboxes.length; i++) {
        if (checkboxes[i] != source)
            checkboxes[i].checked = source.checked;
    }
}
</script>
<form method="get" id="cat-form">						

<fieldset>
	<input type="checkbox" name="ecsall" id="ecsall" onClick="toggle(this)" <?php if ( ! empty($ecs01) && ! empty($ecs02) && ! empty($ecs03) && ! empty($ecs04) && ! empty($ecs05) && ! empty($ecs06) ) { echo "checked"; } ?> />
	<label for="ecsall">Toggle All</label>
	
      <input type="checkbox" name="ecs01" id="ecs01" value='company' <?php if ( $ecs01 == "company" ) { echo "checked"; } ?> >
      <label for="ecs01">Company</label>	
      <input type="checkbox" name="ecs02" id="ecs02" value='development-opportunities' <?php if ( $ecs02 == "development-opportunities" ) { echo "checked"; } ?> >
      <label for="ecs02">Development Opportunities</label>	
      <input type="checkbox" name="ecs03" id="ecs03" value='gigaplant' <?php if ( $ecs03 == "gigaplant" ) { echo "checked"; } ?> >
      <label for="ecs03">Gigaplant</label>	
      <input type="checkbox" name="ecs04" id="ecs04" value='innovation-hub' <?php if ( $ecs04 == "innovation-hub" ) { echo "checked"; } ?> >
      <label for="ecs04">Innovation Hub</label>	
      <input type="checkbox" name="ecs05" id="ecs05" value='networks' <?php if ( $ecs05 == "networks" ) { echo "checked"; } ?> >
      <label for="ecs05">Networks</label>	
      <input type="checkbox" name="ecs06" id="ecs06" value='university-and-colleges' <?php if ( $ecs06 == "university-and-colleges" ) { echo "checked"; } ?> >
      <label for="ecs06">University and Colleges</label>				                
</fieldset>
<button id="search-submit" class="button">Apply Filters</button>

</form>

Note: the ‘Get’ method shows the string in the URL useful for copy and paste and the ‘post’ method hides the string which maybe useful if you want to have a cleaner URL.