Abbreviation in chart or caption

It’s OK to abbreviate words in charts and captions if needed. If it’s in body copy, use a period after the abbreviated word.

approx. 87 homes

34 avg.

Acct 1234567

kWh / thm

Abbreviation in body copy

In general, don’t abbreviate a word if there’s room to spell it out.

This is based on approximately 87 nearby homes.


Avoid acronyms when possible, unless the acronym is commonly understood by people in the target audience. If you have to use an acronym, make sure to spell it out in the first instance.

Acronym in client name

Follow the client’s conventions.


Common acronyms

Don’t spell them out.


Industry jargon

Rewrite to avoid using an acronym. If that’s not possible, define the acronym the first time you use it.

smart meter

AMI (advanced meter infrastructure)


Acronyms in Opower internal communications

Use real words, people! Acronyms like WUM, PBU, and UUA in internal communications can be confusing, especially for new colleagues.

We started a list of product acronyms to keep track of the alphabet soup, but it’s much better if you just say what you mean.


In general, use the word “and” instead of an ampersand. Exception: You can use ampersands in buttons or places with very limited character counts.

View & Pay



Use bold text with discretion—if everything’s bold, nothing stands out. If you’re using bold, choose helpful keywords. In general, it’s better to bold a phrase than a single word.

You used 30% more than your neighbors.

You’re eligible for a $50 rebate.

You’ll get up to 50% off.

Get a free home energy assessment.


In general, don’t use italic text.

All caps

Never use all caps for emphasis—it feels like shouting. Buttons are the exception.


Make sure all apostrophes are actually apostrophes (’) and not inch marks ('). The difference is subtle, but apostrophes are curly and inch marks are straight.




Capitalization in headings and body copy

In general, use sentence case—start every sentence, heading, and phrase with the first letter capitalized.

Ways to save

Exception: If it’s a proper name or product name, capitalize each word.

Home Energy Report

Exception: Use title case for chart labels and tables.

Efficient Neighbors

Average Neighbors

Don’t capitalize






Commas in a list

Use serial (Oxford) commas to separate all items in a list, including the last item.

Pay special attention to windows that face south, west, and east.

Commas to separate an aside

Use commas to separate asides. For important asides, you can also use em dashes.

Window coverings, like awnings or curtains, can reduce heat in your home.

Currency, costs

In general, round costs to the nearest dollar.

Insights and body copy

Round to the nearest dollar.

This costs you $34 per year.


Use round, logical increments for a chart’s Y axis.

$100, $200, $300

Savings and rebates

Round to the nearest $5.

Get a $65 rebate


For billing info or tooltips, show the exact amount.


If showing energy rates, show the exact amount.


If showing a range, use a hyphen with a space before and after (not an en dash). The dollar sign goes before both values.

$10 - $15

Date, time

Days and months

Short form: Abbreviate to 3 letters, no period.

Mon, Tue, Wed

Jan, Feb, Mar

Long form: Spell out in body copy, or whenever the day or month is framed by other words.

Please reduce energy use on Saturday, August 18.

Don’t use ordinals.

August 18

August 18th

Date ranges

If showing a range, use a hyphen with a space before and after (not en dash).

Dec 2014 - Jan 2015

Include years for both. Exception: Omit the year in tooltips if it appears somewhere else.

Jan 2, 2010 - Feb 4, 2011

Time, hours, minutes

Use “am” and “pm.” Don’t use spaces, periods, or capital letters.


Use figures, but spell out noon and midnight.

9am, noon, 6pm, midnight

In general, don’t show minutes.


Exception: Show minutes if it’s relevant.

Join your neighbors in reducing energy use from 2:30pm - 7:30m.

If showing a range, use a hyphen with a space before and after (not en dash).

9am - 7pm

Exclamation marks

In general, don’t use them. (!!!!!) OK, fine, you can use them sparingly. Overusing exclamations hurts the overall tone—it can make your communication seem unprofessional.

Also, keep in mind that using exclamation marks in an email makes it more likely to be flagged as spam.

Still not sure? Check out this handy chart.

Hyphen, dashes

Hyphen in a range of numbers

Include space before and after.

2pm - 7pm

1,000 - 1,500 sq ft

Hyphen between a word and number


Hyphens in compound adjectives

Use if the compound adjective is before the term it modifies.

Get an energy-efficient furnace this winter

Printed on 10% post-consumer recycled paper using water-based inks

Don’t use a hyphen if the compound adjective is after the noun.

New ovens are very energy efficient

Energy-efficient vs. Energy efficient

Hyphenate this phrase when there’s a noun after it.

An energy-efficient furnace

Don’t hyphenate this phrase when there’s no following noun.

Make your house more energy efficient

Never hyphenate "energy efficiency".

Energy efficiency

Energy-saving vs. Energy saving

Hyphenate this phrase when it’s describing something that concretely saves energy.

Energy-saving habits

Don’t hyphenate this phrase when used as a noun.

Tips for energy savings

Don’t hyphenate this phrase when it’s used as a noun.

Energy saving tips

Email vs. E-mail

Don’t hyphenate email.


Counter-clockwise vs. Counterclockwise

Hyphenate as “counter-clockwise.”


Pick-up vs. Pickup vs. Pick up

When used as a noun, it’s one word without hyphens.

Schedule a free pickup

When used as a verb, it’s two words.

UtilityCo will pick up your refrigerator.

Tune-up vs. Tune up

“Tune-up” is the noun.

You may qualify for a free AC tune-up from UtilityCo.

When used a verb, use two words. "Tuneup" (one word) is never correct.

A certified contractor will tune up your AC free of charge.

Step-by-step vs. Step by step

If used as a heading, don’t use hyphens (Step by step). When using the phrase as an adjective, use hyphens.

a step-by-step guide to saving energy

En dashes

In general, don’t use en dashes. To show a range, use a hyphen with a space before and after.

2pm - 7pm

Note: Yes, en dashes are technically correct in this case... but since people are more familiar with hyphens, we decided to prioritize consistency over technical accuracy.

Em dashes

Use at writer’s discretion.

Keep an eye out for future reports—you can track your progress over time.


Number in headings and body copy

Use numerals.

You’re in the top 5!

Number in a chart

Use numerals. Don’t use ordinals.

Number to show rank

Use ordinals and superscript for 1st, 2nd, 3rd, etc.

You’re the 4th most efficient home!

Number in a date

Don’t use ordinals in dates (3rd, 4th, etc.).

Jan 5

Jan 5th


Use the percent symbol (%). Avoid using the word “percent.”

If showing a range, use a hyphen with a space before and after (not en dash). The percentage sign goes after the second value.

10 - 15%


Use them sparingly (at writer’s discretion). ← See? To avoid a parenthesis, you might try breaking into different sentences, using commas or em dashes, or removing the idea altogether.

If you decide to use a parenthetical aside, make sure it’s short.

Efficient neighbors use the least electricity (they’re the top 20%).


Periods in body copy

Use periods and punctuation. Incomplete sentences or phrases shouldn’t have punctuation at the end.

Periods in display heading

In general, use periods and punctuation.

Please join your neighbors in reducing energy use on August 18 from 2pm - 7pm.

Periods in hierarchical headings

Don’t use periods. Use question marks as needed.

Energy use trends

Billing history

How you’re doing

Ways to save

New! Home Energy Report

What’s next?

Periods in marketing module headings

In general, don’t use them (at writer’s discretion).

Phone number

This is a customizable field—in general, use the format the utility want to use. See examples on the wiki.

Default style

Use a parenthesis around the area code and a hyphen after the third number. Note the space between the area code and number.

(415) 222-2222

Another style for 1-800 numbers

In the U.S., the more common convention is to use hyphens instead of parentheses.


When to use bold

Don’t use bold for phone numbers on web. It’s ok to bold phone numbers on paper reports, but use at your discretion—make sure it looks right in context.


For items not covered here, refer to the AP Stylebook.


In general, avoid semicolons; use them only when absolutely necessary. See how weird that was?


If showing a range, the degree sign (°) and scale (C or F) go after the last value.

10 -15°F

Use a hyphen with a space before and after (not en dash).

Units of measurement

Use numerals and spell out inch, feet, mile. If there are space constraints, abbreviate in., ft., mi. Note: no periods after metric units m, cm, mm.

In general, round up. If you need to be more precise, use decimals, not fractions.

2 inches Alt: 2 in.

1.75 feet Alt: 1.75 ft.

4 miles Alt: 4 mi.

300 Therms Alt: 300 thm

1200 - 1400 square feet Alt: 1200 - 1400 sq. ft.

$35 per square foot

1 3/4 ft




For Hong Kong: Use sq ft for area and litres for water.
For United Arab Emirates: Abbreviate all units.

kWh, kilowatt

When abbreviated, use a capital W.

Therm, thm

Use a capital T in Therms. If abbreviated, it’s thm.



Units (combined gas/electric)

Units represent a combination of electricity (kWh) and natural gas (Therms). This comparison is based on approx. 100 homes most similar to yours.