EV charging cost calculator template

Free build guide: EV charging cost calculator for WordPress

This guide rebuilds the EV charging cost calculator from this site in Gravity Forms: 6 inputs, 4 live results and no submit button. Expect about 30 minutes by hand. The template above is the same form as an import file, and the bundle adds a PDF version of this guide with a screenshot of every setting, plus the stylesheet.

You will end up with:

• Cost of this charge
• Energy from the wall (kWh)
• Cost of a full charge
• Cost per mile

What you need

• Gravity Forms (any license) — Calculation fields are in core.

Everything here is core Gravity Forms. No add-ons.

1. Create the form

1. Go to Forms → New Form and name it EV charging cost.
2. In Form Settings → Form Layout, set the CSS Class Name to fo-live-only. Step 3 uses it to hide the submit button.
3. Leave the form open in the editor; the fields come next.

2. Add the fields, in this order

Field IDs are assigned as you add fields. If yours come out differently, change the {Label:ID} references in the formulas to match your IDs. Settings not mentioned stay at their defaults.

1. Battery size (kWh) · Number · ID 1
Number Format 9,999.99; Default Value 75; Description “Usable capacity, from the spec sheet. 60–80 kWh is typical; a Model 3 Long Range is about 75, a Bolt 65, an F-150 Lightning 98–131.”.

2. Charge from (%) · Number · ID 2
Number Format 9,999.99; Default Value 20; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

3. Charge to (%) · Number · ID 3
Number Format 9,999.99; Default Value 80; Description “80% is the everyday limit most makers suggest.”; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

4. Electricity rate (¢ per kWh) · Number · ID 4
Number Format 9,999.99; Default Value 17; Description “Your home rate from the bill; off-peak EV rates can be 8–12¢. Public fast charging runs 40–60¢.”; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

5. Charging loss (%) · Number · ID 5
Number Format 9,999.99; Default Value 10; Description “Energy lost as heat. About 10–15% on a home Level 2 charger, 15–20% on a 120 V outlet, 5–10% on DC fast charging.”; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

6. Range on a full charge (miles) · Number · ID 6
Number Format 9,999.99; Default Value 280; Description “EPA range, or what you really see.”.

7. Cost of this charge · Number · ID 7
Number Format Currency; Custom CSS Class (Appearance tab) fo-result; tick Enable Calculation, Rounding 2.

( {Battery:1} * ( {To:3} - {From:2} ) / 100 / ( 1 - {Loss:5} / 100 ) ) * {Rate:4} / 100

8. Energy from the wall (kWh) · Number · ID 8
Number Format 9,999.99; Description “What the meter counts, losses included.”; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 1.

( {Battery:1} * ( {To:3} - {From:2} ) / 100 / ( 1 - {Loss:5} / 100 ) )

9. Cost of a full charge · Number · ID 9
Number Format Currency; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 2.

( {Battery:1} / ( 1 - {Loss:5} / 100 ) * {Rate:4} / 100 )

10. Cost per mile · Number · ID 10
Number Format 9,999.99; Description “Dollars per mile. A 30 MPG petrol car at $3.50 a gallon is about 0.117.”; Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 3.

( {Battery:1} / ( 1 - {Loss:5} / 100 ) * {Rate:4} / 100 ) / {Range:6}

3. Hide the submit button

The results are live, so nothing needs submitting. Add this filter to your theme’s functions.php or a code-snippets plugin; it hides the button on any form carrying the fo-live-only class:

add_filter( 'gform_submit_button', function ( $button, $form ) {
	return str_contains( (string) rgar( $form, 'cssClass' ), 'fo-live-only' ) ? '' : $button;
}, 10, 2 );

Or with CSS alone: .fo-live-only_wrapper .gform_footer { display: none; }

4. Put it on a page and make it look like this

Add the form to any page with the Gravity Forms block, or the shortcode [gravityform id="X" title="false" ajax="false"]. The form inherits your theme’s styles; the classes you set in step 2 are hooks for the look you see on this site:

• fo-result on a calculation field makes it the big teal result panel.
• fo-result fo-result--sub makes the smaller secondary figures.
• fo-segmented on a radio field turns it into a segmented switch.
• Two fields on one row is the editor’s own column layout: drag a field beside another and the row splits in half. No CSS class is needed, and the old gf_left_half Ready Classes are deprecated.

The bundle includes the two stylesheets that implement those classes, with notes on matching your brand colours. Without them the form still works; it just looks like your theme’s default Gravity Forms styling.

How the maths works is explained under “How it’s calculated” on the live EV charging cost calculator.