Hot Water Running Cost Calculator & Comparison.
Hot Water Running Cost Calculator & Comparison
See what different hot water systems could cost your household to run before you choose one.
Compare electric storage, heat pump, gas and solar hot water using the same household. See estimated daily, monthly, annual and 10-year running costs — then calculate the potential saving and simple payback.
Compare My Hot Water Costs
Choose the household size and two hot water setups. The calculator applies the same household demand to both so the comparison is like-for-like.
Comparative estimate only. Actual running costs vary with household use, tariff rates, retailer pricing, climate, water temperature, system efficiency, solar production, controls and maintenance. The 10-year benchmark model uses 5% annual energy-cost escalation.
How Much Does a Hot Water System Cost to Run?
Hot water running cost depends on four main things: how much hot water the household uses, how efficiently the system produces it, what the household pays for energy and when the system is allowed to heat.
4-Person Household Hot Water Running Cost Comparison
These benchmark figures compare the running cost of different hot water setups for the same four-person household over ten years.
| Hot Water System | Energy Setup | Estimated 10-Year Running Cost | Why It Changes |
|---|---|---|---|
| Electric Storage | Tariff 11 | $22,973.90 | Resistance heating using general-use electricity. |
| Electric Storage | Tariff 31 | $16,484.00 | Controlled-load pricing reduces the cost of each unit of electricity used. |
| Natural Gas | 4 Star | $13,415.00 | Gas consumption is affected by appliance efficiency and storage losses. |
| Natural Gas | 6 Star | $11,179.00 | Higher appliance efficiency reduces the amount of gas needed for the same hot water demand. |
| Heat Pump | Tariff 31 | $3,620.89 | A heat pump transfers heat rather than generating all heat directly from resistance electricity. |
| Solar Hot Water | Roof / HiLine + T31 Boost | $2,774.00 | Solar heat reduces the amount of purchased boost energy required. |
| Solar Hot Water | Ground / LoLine + T31 Boost | $2,607.00 | Solar contribution and boosting determine purchased-energy use. |
| Heat Pump + Solar PV | Daytime Solar | $1,348.47 | Rooftop PV can provide part of the heat pump's electrical demand during the day. |
| Heat Pump + PV + Load Sensitive Relay | Solar-Aware Control | $524.40 | Heating can be better matched to available surplus solar rather than relying only on a fixed timer. |
Electric vs Heat Pump vs Gas vs Solar Running Costs
Each technology pays for energy differently. Comparing only the purchase price can hide a much larger difference in long-term operating cost.
Electric Storage
Conventional electric storage uses a resistance element. Running cost depends heavily on the electricity tariff and the amount of water reheated each day.
- Simple technology.
- General supply can be relatively expensive.
- Controlled load can reduce energy cost.
- PV timing can change the result again.
Heat Pump
Heat pumps use electricity to move heat from surrounding air into the water, reducing the electrical input required for each unit of useful heat.
- COP affects efficiency.
- Climate affects performance.
- Daytime operation can suit solar PV.
- Smart controls can reduce grid imports further.
Natural Gas
Gas hot water cost depends on the appliance efficiency, gas price and whether the household would retain the gas connection for other appliances.
- Star rating affects consumption.
- Storage systems have standing heat loss.
- Continuous flow avoids tank losses.
- Gas supply charges may also matter.
Solar Hot Water
Solar thermal systems collect heat directly from sunlight and use electricity or gas for boosting when solar contribution is insufficient.
- Solar conditions affect contribution.
- Boost energy remains important.
- Collector orientation matters.
- Tank and household timing affect performance.
Heat Pump + Solar PV
A heat pump's relatively low electrical demand can make it easier for rooftop solar to cover a large portion of hot-water energy use.
- Daytime operation is important.
- Available PV surplus varies.
- Other household loads compete for solar.
- Export value should be considered.
Solar-Aware Control
A load-sensitive relay or similar solar-aware control can react to available household solar rather than assuming generation is available at a fixed time.
- Can reduce grid imports.
- Better follows actual PV output.
- Other home loads still matter.
- Installation and control strategy must suit the system.
Electricity Tariffs Can Change Hot Water Running Cost Without Changing the Tank
A resistance electric hot water system uses essentially the same heating method regardless of tariff. What changes is the price and availability of the electricity supplied to it.
General Supply
The system can normally heat whenever required, but hot-water consumption is charged using the applicable general household electricity rate.
Controlled Load
A dedicated controlled-load arrangement can provide a lower electricity price while restricting the hours in which power is available to the water heater.
Solar PV
Daytime operation can use locally generated solar electricity where enough surplus generation is available.
Fixed Timer
A timer moves heating into a selected period but does not know whether household solar is actually available at that moment.
Load-Sensitive Relay
Solar-aware control can respond to actual available generation and switch the hot water load according to configured conditions.
Free-Power Window
Some electricity plans provide qualifying periods where electricity charges are reduced or waived. Tank capacity and recovery determine how much heating can be shifted into that period.
Can a 3-Hour Free Power Period Run Your Hot Water?
Potentially — but the system must be capable of putting enough heat into the tank during the available period to carry the household through the rest of the day.
Electric Storage
A resistance element can deliver a relatively high amount of heat during a short window, particularly where element output and tank size are suitable.
- Tank size matters.
- Element output matters.
- Household demand must fit the stored capacity.
- Additional heating may still occur outside the free period.
Heat Pump
A heat pump uses less electrical energy but may need a longer operating period because compressor heat output is generally lower than a high-output resistance element.
- Lower electrical demand.
- Longer recovery can matter.
- Storage carries heat beyond the free period.
- Solar PV can supplement the available window.
What COP Means for Heat Pump Running Cost
Coefficient of Performance compares the useful heat produced by a heat pump with the electrical energy it consumes under the applicable operating or test conditions.
Resistance Heating
A resistance element is effectively the baseline: electrical energy is converted directly into heat at the element.
Heat Pump COP
A heat pump can provide several units of useful heat for each unit of electrical energy consumed because much of the heat is collected from surrounding air.
Real-World Efficiency
COP changes with ambient temperature, water temperature, operating cycle and the manufacturer's test method, so a published figure should not be treated as identical performance in every condition.
Running Cost Is Only One Part of Hot Water Ownership Cost
A proper replacement comparison considers purchase price, installation cost, rebates, energy use, servicing and expected system life together.
Purchase & Install
Compare complete installed pricing rather than equipment-only pricing.
Incentives
Eligible heat pumps and solar hot-water systems may qualify for certificates or other incentives.
Energy Cost
Compare annual and long-term energy costs rather than only the first bill.
Service & Life
Maintenance requirements and expected system life also affect total ownership cost.
How the Installed Today Running Cost Calculator Works
This calculator is designed to compare technologies on the same household basis rather than predict an exact future electricity or gas bill.
Same Household
Both selected systems use the same household-size demand factor so you are comparing technology against technology rather than changing the household assumptions.
Technology Benchmarks
Each system starts from its established four-person 10-year benchmark and is scaled for household size.
Energy Escalation
The long-term benchmark incorporates a 5% annual energy-cost escalation assumption rather than assuming today's annual cost remains unchanged for ten years.
Hot Water Running Cost FAQs
What is the cheapest hot water system to run?
Running cost depends on the household and energy setup. Efficient heat pumps using well-matched daytime solar can have very low purchased-energy costs, while solar thermal systems can also substantially reduce boost energy. Purchase price and servicing should be considered separately.
How much does electric hot water cost to run?
Electric storage running cost depends on household demand and the electricity tariff. A resistance system using general-use electricity can cost substantially more than the same basic technology using a lower-cost controlled-load tariff.
Is a heat pump cheaper to run than electric storage?
Heat pumps generally use substantially less electrical energy because they transfer heat from the surrounding air rather than creating all of the heat directly through a resistance element. Actual savings depend on model efficiency, climate, tariff and use.
Is gas hot water cheaper than electric hot water?
It depends on the gas appliance efficiency, gas price and electricity tariff being compared. High-efficiency continuous gas can use less energy than older gas storage, while heat pumps can use substantially less purchased electricity than resistance storage.
Does off-peak hot water save money?
A controlled-load or off-peak tariff can reduce the price paid for electricity used by an eligible water heater. It changes the cost of electricity rather than the fundamental efficiency of the heating element.
Is a heat pump cheaper with solar panels?
It can be. Operating a heat pump when useful surplus rooftop solar is available can reduce purchased grid electricity. The value of the solar electricity that would otherwise be exported should also be considered.
Is a load-sensitive relay better than a hot water timer?
They work differently. A timer follows a fixed schedule, while a solar-aware relay can respond to actual available solar generation or household load conditions. This can improve solar utilisation where properly configured.
Can 3-hour free power make hot water free?
It may allow some or most hot-water heating to occur during a qualifying free-energy period, but zero running cost is not guaranteed. Tank size, heating output, household demand and control setup determine whether additional heating is required outside the free period.
What does COP mean for a heat pump?
COP means Coefficient of Performance. It compares useful heat output with electrical energy input under the relevant test or operating conditions.
Does household size affect hot water running cost?
Yes. More occupants generally create more hot-water demand, although consumption does not increase perfectly linearly because some household uses are shared.
Why compare hot water costs over 10 years?
Hot water systems are long-term equipment. A ten-year comparison makes it easier to see whether differences in efficiency and energy cost become large enough to outweigh differences in purchase and installation price.
Compare What Your Next Hot Water System Costs to Own — Not Just to Buy.
Use running cost alongside purchase price, household size, installation requirements and available incentives to compare the hot water systems that suit your home.
