The next most popular company to switch to was Meridian, with 406 switches.
The only other company to experience a switch deficit was Todd Energy, which was down 71.
There were 26,065 switches across New Zealand between December 31, 2016, and December 31, 2017.
Powerswitch listed Trustpower as the most expensive power company in Tauranga.
However, Trustpower general manager, markets Craig Neustroski said Powerswitch as a data source was more about tracking trends in prices rather than calculating actual savings for consumers.
It was based on an average annual consumption for a medium-sized household (8492 kWh per year), but Trustpower's actual customers used much less – their average consumption was 6158 kWh. The median usage was 5571kWh, he said.
"Therefore the actual amount customers spend is much less than that shown and any differences are much less than that shown.
"Trustpower is a bundled utility provider offering customers packages that include electricity, gas and telco products and as such Powerswitch is not well placed to cater for all the packages and offers we have available in the market.
"Trustpower is also based in Tauranga providing significant employment and support in the community and have a very long relationship with many of our customers, which means that new competitors coming into the area have to undercut us to win customers."
A Mercury Energy spokesperson said Mercury had been rewarding customers with loyalty programmes and providing customers with certainty with fixed-price contracts.
"Our bold customer-led brand has resonated with customers in a highly competitive market previously focused almost exclusively on price.
"We're inspiring customers to enjoy energy in more wonderful ways through offerings including Mercury Solar, giving customers the freedom to generate their own renewable energy."
One Tauranga couple who made the switch was Tam McDonald and his wife.
McDonald said he was getting power bills of up to $200 a month when he decided to knuckle down and compare different companies prices.
"I was with Trustpower for the power and Genesis for the gas. The power bills were getting up, there's only two of us at home, and the bills were approaching $200 at certain times of the year plus $100 on top of that for gas.
"So I decided to have a look at the Powerswitch website, then I delved a bit further by talking to the two companies and then moved over to Genesis," McDonald said.
McDonald said that part of it is about having an awareness.
"I used a few of the calculators on the Powerswitch website, and also approaching the companies and having a civilised conversation with them can be really helpful as well."
Tauranga Budget Advisory Service Manager Diane Bruin said the difference between power companies could make a difference of up to $500 per year.
Power rates change regularly and Bruin suggests you go online to: www.powerswitch.org.nz with your power bill and compare prices.
"Check if your bill is an estimate or actual. Sometimes these can be higher or lower and if you are concerned you can read your own meter," Bruin said.
Tip to save on your power bill
-Turn off appliances that you are not using don't leave TV's in standby mode.
