Before opting for solar panels, one homeowner thought they had found a smart way to keep energy bills down in the meantime. 

The proposed overhaul centered on a 132-gallon (500-liter) attic tank that could be heated on a discounted EV power tariff. The elaborate money-saving solution was shot down in the comments as people pointed to something much simpler that offered similar benefits. 

Here's what to know

In a Reddit post, the homeowner described a pre-solar stopgap: switch to condenser gas central heating, eliminate the current electric-shower and heating-tank setup, and add an attic-mounted tank of about 132 gallons (500 liters) heated on an EV tariff to feed three showers.

Instead of endorsing the tank plan outright, commenters advised comparing it with a heat pump water heater and said utility rebates and tax credits might reduce the upfront price.

While a large tank can help shift energy use to cheaper hours, it does not automatically solve the efficiency question if the water is still being heated with resistance elements. A heat pump water heater, by contrast, is designed from the outset to use much less electricity.

More background

For a household with three showers, hot-water demand can be high enough that timing and recovery rate become major considerations. A large thermal store may help keep the household from running out of hot water, especially if it is charged overnight, but bigger tanks also take up space and can lose heat while sitting full.

Then there is the attic factor. A 132-gallon (500-liter) tank is not a small piece of equipment, and a plan like that raises practical questions about weight, plumbing runs, installation complexity, and whether another system could provide the same comfort with lower overall energy use.

Commenters pushed the discussion toward cost calculations rather than focusing only on the overnight tariff. If a homeowner is already thinking about replacing multiple parts of a hot-water system, the cheapest option over time may not be the one tied to the lowest hourly electricity price.

What can be done?

The first step is to compare total installed cost, expected energy use, available rebates, and the home's actual hot-water demand — not just tank size. It can also help to ask an installer about structural limits, ventilation, and whether future solar production could change which option makes the most sense.

Cala is one company focused on that kind of optimization. Its customizable smart heat pump water heaters help homeowners decrease their energy bills by heating water exactly when it's needed. That can be especially useful for households trying to match hot-water production to off-peak power prices, daily routines, and future rooftop solar output.

The main takeaway is that cheap electricity and efficient water heating are not always the same thing. In many cases, the best option may combine both — accessing lower-cost power when it is available and using equipment that wastes less energy in the first place, which is part of the pitch behind Cala.

"I think you're over complicating this," one commenter wrote. "Install a large heat pump water." 

"A heat pump water heater can be powered by solar, be controlled by Wi-Fi, has leak detection and auto shut off, will cool and dehumidify the attic, in the USA most utilities will offer a rebate to install one, and there may be state and federal tax credits," another added. 

Where can I learn more?

Homeowners worldwide are looking to the benefits of heat pumps and heat pump water heaters. While some encounter difficulties, there is still plenty to like about the technology if it can be installed.

• In the Netherlands, homeowners were told to rethink EV charging and heat pump upgrades as grid congestion worsened.

• In the U.K., one homeowner chased a 400%-efficient heat pump but encountered some hurdles.

• In Vermont, a freezing winter still left one homeowner calling heat-pump savings a no-brainer.

A heat pump's effectiveness ultimately comes down to balancing tariff timing, equipment efficiency, and the limits of the house and local grid.

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