What Does Time-of-Use Pricing Mean for a Home With EV Charging, Electric Hot Water and Solar?

Time-of-use pricing means the price of electricity changes depending on when you use it. For a home with an EV, electric hot water and solar, it can create genuine savings, but only when those systems are coordinated around the household’s actual energy pattern.

The cheapest advertised rate does not necessarily produce the lowest overall bill. What matters is when the home imports electricity, when it generates solar, what it earns from exporting, and whether its largest loads can be moved without affecting daily life.

The plan applies to your whole home

A flat-rate plan charges approximately the same usage rate throughout the day. A time-of-use plan divides the day into periods such as peak, off-peak, night or free-power hours.

The lower off-peak rate may be balanced by a higher peak rate, a different daily charge or a lower solar buyback rate. That means the plan affects more than EV charging. It also changes the cost of cooking, heating, lighting and everything else running during the more expensive periods.

The Electricity Authority says time-of-use plans tend to suit households that can consistently move substantial electricity use into off-peak periods. EV charging and electric hot water are among the clearest opportunities because they can often operate without needing to run immediately. Electricity Authority guidance

Before changing plans, look at several weeks of smart-meter data rather than relying only on the headline discount.

EV charging is usually the easiest load to move

An EV is often parked for far longer than it needs to charge. A smart charger can use that flexibility to delay charging until an off-peak period, while still having the vehicle ready by the required departure time.

If the EV is regularly at home during the day, solar charging may be another option. Using surplus solar directly can reduce the amount exported for a lower buyback rate and avoid purchasing that energy later. EECA notes that daytime EV charging can materially increase a household’s solar self-consumption. EECA solar research

The better choice depends on the plan. Overnight grid charging may be cheaper on one plan, while daytime solar charging may deliver more value on another. A solar-aware smart charger can help the home use either strategy automatically.

Electric hot water can store energy for later

A hot-water cylinder is effectively a store of thermal energy. It does not always need to heat water at the same moment that hot water is being used.

Depending on the system, the cylinder may be scheduled to heat during cheaper overnight periods or during the middle of the day when solar production is available. This can make hot water one of the most useful flexible loads in the home.

However, the existing control arrangement needs to be understood first. Some cylinders are already connected to a controlled supply managed by the electricity network. Others may require suitable switching, monitoring or control equipment before their operating times can be changed properly.

The goal is not simply to turn the cylinder off during peak periods. It is to ensure the household still has reliable hot water while using the most appropriate source of energy.

Solar introduces a second set of prices

With solar, there are two values to compare:

• The price avoided by using solar within the home

• The buyback rate received for exporting it

Self-consuming solar is often valuable because every unit used directly replaces electricity that would otherwise be purchased. But some plans now offer different export values at different times, especially when electricity is more valuable to the network.

New Electricity Authority requirements were intended to make both off-peak import plans and peak-time export rewards more widely available from July 2026. Electricity Authority decision

Solar, EV charging and hot water therefore need to be considered together. Sending solar to the grid while buying electricity later may make sense under one plan, but using that solar to heat water or charge the EV may be better under another.

Cheap electricity does not remove capacity limits

Moving several appliances into the same cheap period can create a new problem. If the EV charger, hot-water system, heat pumps and other appliances all start together, the home’s instantaneous demand may still be high.

Time-of-use pricing changes the cost of electricity. It does not increase the capacity of the incoming supply, switchboard or circuits.

Smart charging, load management and staged operating times can prevent large loads from stacking unnecessarily. These controls should be planned around the home’s electrical foundation, including Capacity, Protection, Distribution, Condition and what will be needed to keep it Future Ready.

When is an electrical assessment worthwhile?

An assessment is useful when a home is adding or coordinating several substantial electrical systems, particularly if the switchboard is older, the available supply is uncertain or further upgrades are planned.

For a Dunedin home, a Power Integrity Review™ can establish what the existing electrical foundation can support, identify any constraints and help determine the correct order for solar, EV charging, electric hot water and load-management decisions.

The takeaway

Time-of-use pricing can work particularly well for a home with flexible electrical demand. The greatest value usually comes from coordinating when the EV charges, when water is heated and how solar is used or exported.

Start with the household’s real energy pattern, then make sure the electrical foundation can support the way those systems will operate together.