The arrival of Memorial Day in Hawaii signaled the unofficial start of summer, and with it a higher demand for electricity as fans and air conditioners rev up to deal with the heat.

Hawaiian Electric said energy use for homes without rooftop solar systems during the warmer months from June to October is generally about 10% higher than other times of the year, based on an analysis of data from residential customers from 2017 to 2020.

“Generally, bills often increase over the summer months because higher temperatures trigger increased use of air conditioners,” said Hawaiian Electric spokeswoman Shannon Tangonan. “But even if a customer doesn’t have an air conditioner, the heat and humidity also cause other appliances such as refrigerators and freezers to work harder to keep temperature, especially if they’re kept outdoors or in garages.”

Although this can vary from household to household, even homes with rooftop solar can experience an increase during warmer months, she said.

Air conditioning is one of the biggest energy users in a home, according to Hawaii Energy, a ratepayer-funded initiative that helps families and businesses make smarter energy choices. Hawaii Energy recommends using fans instead, when possible.

This year, however, residential customers may be in for a triple whammy.

Residential energy usage also went up, on average, during the pandemic, according to Hawaii Energy Executive Director Brian Kealoha.

When the pandemic hit in March 2020, the average customer on Oahu was using about 20 to 25 kilowatt-­hours more per month, according to Kealoha. That translates to a possible bump of maybe $7 a month for those without solar.

Fortunately, that increase in usage was offset by a drop in fuel oil prices due to a decline in worldwide demand, and the average bill may have stayed about the same.

Still, for some, energy bills spiked during the pandemic, even for those with solar systems due to higher usage while staying at home. Multigeneration households, in particular, he said, were susceptible because more people are using energy in the home.

“We also saw some pretty big fluctuations,” Kealoha said. “Certain households, their energy usage was 50% to 75% more. It really depended on the home situation. I can’t speculate to knowing all the reasons. If you have a lot more people at home, especially last March and April, you were using more energy because you weren’t going out.”

For those who continue spending more time at home and working from home, that trend will likely continue as temperatures climb this summer and as fans and air conditioners go on.

Unlike last summer, however, fuel prices worldwide are now on an upward trend.

If using air conditioning, it’s a good idea to get the system tuned up. Cleaning or replacing filters can increase the unit’s efficiency by up to 15%. Hawaii Energy offers a $75 rebate for tuneups from participating contractors.

This will help by making the air conditioner more efficient. But it’s a good idea to schedule that early, Kealoha said, because by July, most contractors are booked.

Generally, August, September and October are the highest energy usage months due to cooling costs, he said.

Becky Gustafson of Mili­lani is a big believer that a few changes can make a difference in her electric bill. Due to more remote work at home last year, she saw her energy costs spike.

Gustafson has had a solar PV system for at least eight years, but also changed every light bulb in her four-bedroom house to more energy-efficient LEDs, including the ones in the refrigerator. She also has Energy Star appliances.

In May, she upgraded to two solar fans — and got a rebate on them — making a huge difference in keeping the house cool. She has two split air-conditioning systems but is keeping them off until later this summer.

“We have not turned on our AC yet,” she said. “We’re trying to hold out till July 1.”

Record-high temperatures in the summer of 2019 resulted in a surge in demand, resulting in a 12% jump in electricity usage for the month of July and higher energy bills, according to Hawaiian Electric.

This past Memorial Day weekend was a hot and humid one, resulting in record high of 86 in Lihue on May 30 and temperatures in the mid-to-high 80s for the month. That was no match for May 2019, though, when temperatures in Kahului soared to a record high of 96 degrees.

The National Weather Serv­ice Climate Prediction Center predicts below-normal monthly temperatures for Kahului and Hilo this summer, but equal chances for above, near or below normal temperatures for Honolulu and Lihue in June. Summer officially starts June 20.

Hawaii’s average electricity retail prices, at 28.7 cents per kWh, are the highest of any state, according to the U.S. Energy Information Administration. That is in part because the state relies on petroleum for more than 60% of its electricity generation.

Hawaiian Electric said this is due to Hawaii’s geographic isolation and the cost of imported oil, which fluctuates, to power many of the islands’ generators.

Fuel and purchased power from independent producers make up roughly half of a typical bill, according to the utility.

Kealoha said one of the biggest variables is that Hawaii still relies predominately on fossil fuels for generation.

“The quicker we can transition to a cleaner, renewable generating situation, the better,” he said. “Not only will it help reduce bills, it will minimize the variability. We were lucky that oil prices went down last year in the midst of all this.”

Besides air conditioning, Kealoha said water heaters use a lot of energy, particularly without a solar water heater.

Shortening shower times by two minutes could save up to $56 per person a year for those without solar water heating, he said. Investing in a solar water heater could save up to 40% on the electricity bill for families of four or more.

After that, highest energy users include smaller-load appliances like refrigerators, dryers and washing machines.

When purchasing or replacing an appliance, look for the Energy Star logo, which will save money in the long run. Rebates are available for the purchase of Energy Star appliances and solar water heaters.

Hawaii Energy also says peeking in the fridge and a heated oven wastes energy, and that cooking outdoors can keep a home cooler over the summer.

To save energy while working from home, Hawaii Energy recommends taking advantage of natural light, putting computers on sleep settings and using a desk lamp instead of whole room lighting.

Laptop computers, printers and charging devices are not necessarily the biggest energy users, but they use standby power when not in use, and in aggregate can contribute to higher monthly energy bills.

This may have been a contributing factor last year, when parents and kids were on their computers eight to nine hours or more a day. If plugged into smart power strips, a family could save up to $10 a year.

“There’s not one silver bullet: Do this and your bill’s going to come down 50%,” Kealoha said. “It’s taking a lot of different actions and cumulatively you can make a difference.”

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Hawaii Energy Tips

>> Use fans instead of air conditioners when possible.

>> If using an air conditioner, be sure to shut it off when things cool off. Many systems can be set to automatically turn on and off as needed.

>> Make sure the dishwasher is fully loaded and air dry instead of using the heat dry setting.

>> Purchase Energy Star appliances and equipment to ensure optimal energy efficiency.

>> Perform regular maintenance and tuneups on solar water heaters and air conditioners (Hawaii Energy has rebates for both).

Rebates are available at hawaiienergy.com/for-homes/rebates. More energy savings tips are available at hawaiienergy.com/for-homes/tips-to-save-energy.