Which is actually more eco-friendly/cost-effective, hot water, gas or electric? [EcoCute vs EcoJoes]

09/04/2025

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Hello everyone, this is DIY Renova.

When renovating a home by self-renovating or DIYing, "What should we do with the hot water heating system?" is a very big theme. especially,

Whether to pull the gas pipes
Should I cook induction?
How to balance utility costs and environmental impact

I'm sure there are many people who are worried about this from this perspective.

In this article,

EcoJoze (High-Efficiency Gas Water Heater)
Ecocute (heat pump type electric water heater)

We will thoroughly compare the following and explain in an easy-to-understand manner, including an engineering perspective, CO2 emissions, and future prospects: "Which one is really eco-friendly and cost-effective?" If you're wondering which one to choose, please refer to this.

If you're wondering "How much renovation or remodeling can I actually do on my own home?" or "Where should I even start?", please visit this page. If you're looking to learn more about specific renovation processes or construction details, don't miss this page as well!

So, here you go.

Table of Contents

Let's organize what to compare

Comparison items	EcoJoe (Gas)	Ecocute (electric)
Heat source	City gas (LNG)	Power (heat pump)
Hot water efficiency	Approximately 95%	COP3.2 (effective 320%)
Initial cost	Approximately 200,000 to 250,000 yen	Approximately 350,000 to 600,000 yen (Subsidy up to 130,000 yen)
running cost	Approximately 14 yen/kWh	Approximately 9-12 yen/kWh equivalent (Late night power)
CO2 emissions	Approx. 0.19 kg-CO2/kWh	Approximately 0.12 kg-CO2/kWh (assumed by Tokyo Electric Power Company)
Lifespan and update estimate	10-12 years	15 years and

Which is better in terms of running costs?

Let's estimate with specific numbers.

[Prerequisites]

Hot water: 250L/day (family 3-4 people)
Temperature difference: 15→40℃ (ΔT=25℃)
Annual heat: equivalent to 2,650 kWh

[Annual Utilities]

EcoJouze: 14 yen x 2,650kWh ≒ 37,100 yen
EcoCute: 9-12 yen x 830kWh (COP3.2 equivalent) ≒ 7,500-10,000 yen

→ There is a possibility that the difference of 20,000 to 30,000 yen or more per year.

Comparison of initial costs and subsidies

EcoCute has high initial costs, but it is currently subject to government subsidies (2024 energy savings, up to 130,000 yen). This will limit the actual initial difference to around 70,000 to 100,000 yen.

If you divide this by the difference in running costs (20,000 to 30,000 yen per year),Recoverable in approximately 3 to 4 years. After that, the structure will save you every year's utility bills.

Step A: Electricity (Ecocute)

Annual energy = 2,650 ÷ 3.2 ≒ 830 kWh/year (main example)
Annual electricity bill = annual energy × unit price as you like (easy to reduce it by using late-night and renewable energy plans)

Step B: Gas (EcoJoe)

Gas input per year = 2,650 ÷ 0.95 ≒ equivalent to 2,790 kWh
Annual gas usage = 2,790 ÷ 12.5 ≒ 223 m3/year (approximately 13A)
Annual gas fee = Usage × Unit price ± Basic fee (Tokyo Gas ismonthlyUp and down with raw material costs adjustment)
→ For specific unit prices, see "unit fees" for meter reading month. Recalculate your home details or the latest announcement.Tokyo Gas

"Which is cheaper" can sometimes be overturned by the use of electricity (late night, dynamic pricing, self-consumption of solar power) and the unit price of gas (regional and monthly raw material costs adjustments). The quickest correct answer is "recalculation" for each house.

Comparison between CO2 emissions and environmental performance

Annual CO2 emissions

EcoJoe: Approx. 0.19kg x 2,650kWh ≒ 500kg CO2
EcoCute: 0.12kg x 830kWh ≒ 100kg CO2

→ EcoCute isReduced by about 80%. The higher the reenergized energy ratio of the power source, the more advantageous it will become.

Gas also has an invisible greenhouse effect, which means methane leakage (the warming potential for 20 years is 80 times more than CO2), so in reality,The difference opens even moreIt's possible.

There are some situations where gas is superior in terms of time savings and comfort.

For example, if you want to continue using the shower or use bathroom heating at the same time, the instantaneous boiling ability of a gas water heater (10-20kW level) is what you can do.

Since EcoCute is a tank type, if a large amount of hot water exceeds the tank capacity is continuously drained.

For this reason, in some cases, "houses with a lot of visitors," "cold regions," and "homes that are particular about baths," the explosive power of gas-powered machines is likely to win.

A story about comfort and power (what is "number")

Gas "No. 〇" isEstimated amount of hot water (Δ25℃) that can be produced per minute. No. 24 is ``24L per minute''. Simultaneous hot water supply such as simultaneous use of kitchen and bathroomIt's resistant to. In houses with many visitors or households that simultaneously turn the bathroom heating into gas, there are times when gas is the winner.Sunre Fre
EcoCute is a tank type.Continuous use for long periods of time exceeding tank capacityThere is a risk of running out of water, such as "large capacity tanks," "reheating during the day," and "spring up during the day due to excess sunlight."Operational designis the key.

Practical solutions for cold regions, draining water, and installation spaces

For cold regions, choose "cold region specifications." Check the -20℃ compatibility notes and conditions that "boil can be heated even in low outdoor air." Some models have a note that the full boiling rate is limited between -20°C and -25°C, soPlease check the manual's proviso.Daikin
To prevent water drainage, there is a three-piece set: capacity, operation schedule, and water saving equipment.
Examples: Use 370L to 460L, once during the day, and use a water-saving shower head in conjunction with a sub-boiling.
The installation space is "70cm wide x 80cm deep x 200cm high" + delivery route (bending stairs, gates) + concrete foundation (anchor) + drainage. For the 300kg class, advance confirmation of the "transport route" and "base strength" is essential.

Is it good to pull gas pipes just for "Kenta-kun"?

There are many cases where you want to use a gas-type (Kenta-kun) dryer, but both cooking and hot water are powered. in this case,Pull city gas just for Kenta-kunWhat is the cost-effectiveness?

Initial cost

City gas intake: 100,000 to 150,000 yen
Gas tap and Kenta-kun construction: 100,000-150,000 yen
Kenta-kun: Around 200,000 yen

→ Total: Approximately 400,000 to 500,000 yen

Monthly running costs

Gas fee per serving: 40-50 yen
Use it every day for 1,500 yen + basic fee (approx. 750 yen)

→ Operating costs around 25,000 yen per year

Comparison with electric (heat pump dryer)

Price: 70,000 to 130,000 yen
Electricity fee per session: 25-30 yen
Annual utility bill: Approximately 10,000 yen

→ Running difference: Approximately 15,000 yen/year → To return on investmentOver 20 yearsIt takes

→The two are almost equal in terms of CO2 emissions. Electricity, which is becoming more renewable, has a higher future prospect.

"Really profit and loss" for those who want to introduce Kenta-kun

In the official catalog example, 6kg is about 96 yen per session and 9kg is about 149 yen per session (explaining the premise of LP gas and electricity). The time savings are overwhelming,Rainy weather, pollen, nighttimeIt's resistant to.Rinnai
however,New gas faucet installation, exterior wall opening, moisture drainage duct, and platform installationA set of installation work and a monthly basic fee are charged.
The electric competition is a "drum heat pump dryer." Only power per sessionSelf-consumption of sunlight surplusIt goes well with. It dries for a long time, but is energy-saving and quiet.
Conclusion: If you have a household with a high value in how fast it dries, and you have a lot of laundry rotations, then Kenta-kun will do it. Conversely, "sunlight x all-electric"I want to keep my total runningIn that case, electric HP drying is more likely to be optimal.

Issues and solutions for heat pumps

Preventing water drainage

Reheating settings during the day, use of excess solar power, and adopt a large capacity tank of 370L or more

Prevention of freezing

Selected model for cold regions (compatible with -20℃ outside air)

Equipped with installation space

Width 70cm x Depth 80cm, height just under 2m. Foundation installation and weight is over 300kg, so please check the delivery route.

Conclusion: EcoCute is an advantage in both eco-friendly and cost-effectiveness.

Utilities: 20,000 to 30,000 yen cheaper per year
CO2 emissions: Reduced by approximately 80%
Subsidies included: Initial costs are also small in real difference

Gas is superior to "explosive power," "small and cold areas," and "easy to introduce," but without these conditionsElectrical systems are clearly advantageous in the medium to long termIt can be said.

I pull gas just to introduce Kenta-kun.This is also low in terms of cost-effectiveness unless you value the great benefits of saving time and dry quality.

Summary: What is the correct answer for you?

How was the article?

To summarise the above mentioned details, the following is as follows:

conditions	Recommended hot water supply method
All-electricity-oriented, with sunlight	EcoCute is the only choice!
There are many visitors who are worried about the water draining	Eco Joes + tankless hot water supply
The house is too small to put tanks	Eco Joe
Highly environmentally conscious and long-term eco-oriented	EcoCute
I'll turn Kenta-kun every day	City gas + gas dryer + (electricity is OK for hot water)

Actual selection flow chart (directions to avoid getting lost)

"Can I place the tank?": Delivery, foundation, clear firewall → If it can be placed, it's EcoCute's favorite. If you can't put it in, go to gas.
"The necessity of simultaneous hot water heater": Simultaneous use of kitchen + shower + bathroom heatingDailymosquito. If yes, gas is dominated.
"Cold region?": -15 to -25°C. If yes, it's cold-climate (ecocute) or gas.
"Will electricity be used cheaply?": There is sunlight and the late-night price is low. If yes, ecocute is superior.
"Drying needs": Dry once or twice a day.The value of quick dryingIf it's expensive, go for Kenta-kun + (for hot water supply, use either).
"CO2 priority": Renewable energy menu selection and heat pump efficiencyElectricity is growing rapidly.east