The ANZ has warned that the Reserve Bank's big rate cut will hurt savers more than it will benefit mortgage holders with deposit rates likely to fall.

"Given how low interest rates now are, a drop in deposit rates is likely to have a bigger impact on elderly savers than a drop in lending rates on home owners," said Ben Kelleher, ANZ's acting managing director retail and business banking.

All five major banks have announced cuts to home loan and savings rates in the wake of the Reserve Bank's official cash rate cut.

The RBNZ slashed the cash rate by 50 basis points to 1 per cent today - a new record low for New Zealand's cash rate.

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ASB was the first bank to move on cutting its home loan and saving rates but it has since been joined by Westpac, BNZ, Kiwibank and ANZ.

ASB's variable home loan interest rate will fall from 5.7 per cent to 5.2 per cent and its revolving credit Orbit home loan will drop from 5.75 to 5.3 per cent.

Those changes will come in from August 14 for new customers and August 21 for existing customers.

It is more of a shaving for its fixed rate. It will slice just four basis points of its two year fixed term rate dropping it to 3.75 per cent making it the lowest two year fixed rate available at a major bank.

ANZ lowered the interest rates on its Floating and Flexible home loans by 0.50 per cent, from 5.69 per cent to 5.19 per cent.

It said it would be reviewing deposit rates.

ASB will drop its on-call savings rate by five basis points.

Craig Sims, ASB executive general manager retail at the ASB, said it was limiting its cut on deposits to its on call savings accounts.

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"This is about meeting the expectations of our customers and making a deliberate choice to put them first.

"We believe our new lower rates provide a fair and considered outcome for borrowers while also balancing the needs of our savings customers."

The banks are heavily reliant on deposit holders to help fund their loan books and have been cautious about cutting those rates.

Sims urged borrowers to make the most of the low interest rate environment.

"Now is an ideal opportunity for customers to review their home loan. Customers should consider whether to adjust the ratio of fixed versus floating if they have split their mortgage or whether changing from monthly to fortnightly payments would save them money.

"This is also an opportunity for customers to make extra payments or increase their regular payments while interest rates are low."

Westpac will also reduce its floating home loan rates dropping its Choices Floating rate by 45 basis points to 5.34 per cent and its revolving Choices Everyday rate by 40 basis points to 5.44 per cent.

The changes come into effect on August 12 for new customers and on August 26 for existing customers.

But there was no shift in its fixed term rates.

Westpac will also drop the rates on its Simple Saver, Online Saver, Cash Management and Ready Access accounts by five basis points. This comes into effect from August 12.

BNZ will cut both its fixed and floating rates. Its floating rate will drop 50 basis points to 5.3 per cent while its two year fixed term rate will fall four basis points to 3.75 per cent - matching the ASB rate.

It has made no change to its deposit or on call savings rates.

Kiwibank will cut 50 basis points off all its variable rates lowering its variable home loan rate to 5.15 per cent, revolving rate to 5.2 per cent and offset rate to 5.15 per cent.

The cuts make its variable rate the lowest in the market almost more than 80 per cent of home loans are on fixed terms currently.

Kiwibank left its fixed rates unchanged.

It also cut some of its deposit rates. Its 32 day Notice Saver rate will drop 40 basis points to 1.7 per cent and its 90 day Notice Saver rate will drop 40 basis points to 2.7 per cent.

The changes comes into effect on August 12.

Canstar New Zealand general manager Jose George said the extent of the official cash rate cut was a surprise but was good news for borrowers.

"Banks would have built in expectations of a 25 basis point cut, and another one later in the year - not such a big cut now.

"Home loan rates are already being cut by some banks and we would expect others to follow suit."

George said it was a good time for borrowers to consider if their mortgages were structured to take advantage of the cut.

"For those who rely on savings, such as retirees, this news will not be welcome. However we would expect banks to be reluctant to push savings rates down too far, too fast."