Essential Takeaways
- Tankless water heater sizing depends on your home’s peak hot water demand and the incoming water temperature.
- Thermo Direct will calculate your flow rate, measured in GPM (gallons per minute), based on the number of fixtures running simultaneously.
- Gas tankless heaters typically handle higher flow rates than electric models, making them better suited for bigger households.
- Proper sizing with Thermo Direct guarantees you never run out of hot water while avoiding oversized equipment.
If you’ve ever run out of hot water while taking a few showers, you’ve definitely at least thought about upgrading to a tankless water heater. But you’ve probably also thought, what size tankless water heater do I need? There are a few factors to consider when answering this question, and, as your friendly local plumber, Thermo Direct is here to provide them. Read on below and learn why we are the right team to get you endless hot water.
The Short Answer – It Depends on Your Hot Water Demand
When it comes to tankless water heaters, there is no one-size-fits-all answer. A four-person house in Raleigh, NC, might need a completely different system than a four-person house in Durham.
It all comes down to how your household uses hot water, and this is called peak demand. This comes from something like taking a hot shower while someone is doing the dishes. Tankless water heaters don’t store water but heat on demand, meaning you will need the right size and heating capacity for your house.
What Makes Tankless Water Heaters Ideal for Large Homes?
With tankless water heaters, you can shower and do the laundry and the dishes at the same time. Since they heat water continuously as it flows through, you’re not limited by a classic 40- or 50-gallon storage tank, which can mean no hot water with repeated use. This makes them particularly attractive for homes with multiple bathrooms or growing families.
Tankless water heaters also take up way less space than a traditional tanked model. For larger homes with multiple heating zones, you can even install different smaller units throughout the house for faster hot water delivery. Thermo Direct can help you decide on how many tankless units you need.
Finally, tankless water heaters have fantastic efficiency, so your energy savings will appear quickly. Tankless units only fire up when you turn on a hot water tap, which typically translates to 8-14% lower energy costs. Over a 20-year lifespan, these savings really add up.
What Size Tankless Water Heater Do Large Households Need?
When it comes to how to size a tankless water heater, you can find your peak demand yourself or have a Thermo Direct plumber do it for you. Here are the tankless water heater sizing guide steps from the US Department of Energy:
- Step one: List the number of devices that use hot water.
- Step two: Add up their flow rates. Let’s say you expect to simultaneously run a hot water faucet with a flow rate of 0.75 gallons per minute and a showerhead with a flow rate of 2.5 gallons per minute.
- Step three: Check the temperature rise. Subtract the incoming water temperature from the desired output temperature. Unless you know otherwise, assume that the incoming water temperature is 50ºF.
Once you have these peak demand numbers, a Thermo Direct plumber, with professional tankless water heater sizing experience, will determine what kind of heating capacity your tankless water heater needs. For example, for a large household needing 7 to 8 GPM with a 60-degree temperature rise, you’re looking at a unit rated for at least 8 to 9 GPM at your specific temperature rise.
Are There Drawbacks to Tankless Systems in Large Homes?
Tankless water heaters have a higher upfront cost than traditional tanked models. And if one tankless water heater is not enough for your big house’s peak demand, you may require a few smaller units, making the cost quite high.
Tankless water heaters also need yearly maintenance to deal with scale buildup, especially in areas with hard water. If you ignore this maintenance task, you can find yourself with a leaking water heater. Gas water heaters require a dedicated gas line, which can be costly to install. You can learn more about the differences between gas and electric water heaters below.
Gas vs. Electric, Which Type Works Best for Large Households?
There are two different types of tankless water heaters: gas and electric.
Gas water heaters
Gas water heaters are workhorses and typically have higher flow rates at the temperature rises we need here in North Carolina. But they are more upfront, mainly because they require proper venting, either through your roof or the wall. They also require dedicated gas lines, so the installation price increases if you need a new one.
Electric water heaters
Electric tankless heaters are cheaper and simpler to install and maintain, but they have limitations for bigger households. Most residential electric units will max out around 3 to 4 GPM at the temperature rises we need here in North Carolina. For a large household, you’d likely need multiple units or limit simultaneous hot water usage.
Due to their higher flow rate, gas water heaters are more suitable for larger households.
Flexible Financing Options for Raleigh-Durham Homeowners
Upgrading to a tankless water heater is a significant investment, especially for larger systems that are needed in bigger homes. This is why Thermo Direct offers flexible financing options specifically designed for Triangle-area North Carolina homeowners. Partnering with companies like Goodleap and Optimus, we offer monthly payment plans that work with your budget and schedule.
Areas We Serve Across the Triangle
Serving homeowners across:
- Raleigh (27609)
- Rolesville (27571)
- Pittsboro (27228, 27312)
- Wake Forest (27587)
- Apex (27502)
Ready to Upgrade? Schedule Your Tankless Water Heater Consultation Today
If you’re looking for a local plumber for a tankless water heater setup, it’s never been easier than with Thermo Direct. Our experienced technicians will assess your current setup, calculate your actual hot water demand, and recommend the perfect system for your household. Don’t waste another day being choosy with your hot water. Call us today to take the first step toward endless hot water comfort.
Frequently Asked Questions
How do household size and number of bathrooms affect the sizing of a tankless water heater?
If your household size is, say, four people, as opposed to three, the amount of hot water used goes up. Multiple bathrooms also mean more water fixtures for potential simultaneous use. This is all calculated in your peak demand when figuring out the flow rate GPM of your tankless water heater.
Will a tankless water heater work during a power outage?
Even gas tankless heaters need electricity to run their control systems and ignition. During power outages, they won’t operate. However, they’ll start working immediately once power returns, unlike tanked heaters that need time to reheat stored water.
Can I install a tankless water heater myself?
We strongly recommend professional installation. Gas units require proper venting and gas line sizing, while electric units need specific electrical configurations. Improper installation is dangerous.
Can tankless water heaters handle hard water?
Yes, but hard water with high mineral content, like calcium and magnesium, can cause buildup that reduces a unit’s function if not maintained. If you live in an area with hard water, consider investing in a water softener to remove minerals and reduce the frequency of descaling.
