Understanding Tankless Water Heaters
Tankless water heaters heat water only when you need it. This means they don’t store hot water like traditional tanks do. Choosing the right size depends on how much hot water you use and how much temperature increase you need.How Tankless Water Heaters Work
A tankless water heater heats water directly as it flows through the unit. When you turn on your hot water tap, cold water enters the heater and passes over a heating element or gas burner. This instantly warms the water without storing any in a tank. Because it heats water only when you need it, you don’t waste energy keeping a tank full all day. This can save you money on your energy bill. But tankless heaters must be sized correctly to handle your household’s water use at peak times.Types of Tankless Water Heaters
There are two main types: electric and gas tankless water heaters. Electric units are usually smaller and cost less to install. They work well for homes with low to moderate hot water needs. Gas tankless heaters use natural gas or propane. They can provide higher flow rates, making them better for larger families or homes with more hot water use. Gas models often have a longer lifespan, but installation is more complex and costly.Benefits of Going Tankless
Tankless water heaters save space because they are compact and can be wall-mounted. They also last longer than tank models, often over 20 years with proper care. You get endless hot water since it heats on demand, so you won’t run out during showers or laundry. Plus, you can save on energy because they don’t keep water hot when it’s not needed. If you live near Anaheim, CA, Splash Plumbing can help you pick the right size tankless water heater and install it quickly.Determining Your Household Hot Water Demand
To pick the right tankless water heater, you need to know how much hot water your household uses. Think about when you need the most hot water, how much water flows through your taps, and how many things use hot water at the same time.Identifying Peak Usage Times
Look at when your family uses the most hot water. This usually happens in the morning when showers, dishwashers, and washing machines run. Evening meals and laundry can also create peaks. Write down the times during the day when multiple fixtures run hot water together. This helps you know how much your heater must supply at once. Keep in mind: if your family gets ready at the same time or runs several appliances together, your water heater needs to handle that peak without running out of hot water.Calculating Flow Rate Requirements
Flow rate means how many gallons of water per minute (GPM) flow through your taps. You need a tankless water heater that matches or exceeds this flow rate. Here’s a simple list for common fixtures and their estimated flow rates:- Shower: 1.5 to 2.5 GPM
- Kitchen Faucet: 1.5 GPM
- Bathroom Faucet: 0.5 to 1.0 GPM
- Dishwasher: 1.0 to 2.0 GPM
- Washing Machine: 2.0 GPM
Factoring in Simultaneous Appliance Use
Think about how many appliances and fixtures will run at once. For example, if two showers, a dishwasher, and a washing machine are all on, your heater must support all of them together. Ignoring this could mean not enough hot water or inconsistent temperatures. To avoid this, list all appliances likely used simultaneously and add their flow rates. When buying or sizing your tankless water heater, plan for your family’s busiest times. If you live near Anaheim, CA, and need help picking or installing the right unit, Splash Plumbing can guide you through the process.Key Factors That Influence Sizing
Choosing the right size for your tankless water heater depends on several important details. This includes where you live, how many people are in your home, and how many water fixtures or appliances you use. Each factor affects the water temperature and flow you need.Climate and Incoming Water Temperature
Your local climate plays a big role in sizing your heater. If you live somewhere cold, the water entering your system will be colder. This means your heater has to work harder to raise the water temperature to a comfortable level. For example, in cooler regions, you’ll need a unit that can handle a larger temperature rise. This is the difference between the incoming cold water and the hot water you want. The colder the incoming water, the more powerful the heater needs to be. If you live in a warmer area, like Southern California, you won’t need as high a temperature rise. This lets you pick a smaller unit that uses less energy. Knowing your area’s average cold water temperature helps ensure you get the best size without wasting money.Family Size and Lifestyle Habits
How many people live in your home affects how much hot water you’ll use. A family of five will need more hot water than a smaller household. But it’s also about how you use water daily. If your family takes long showers, runs multiple appliances at once, or has high water usage during certain times like mornings, you’ll need a higher flow rate from your tankless heater. Think about your lifestyle habits too. Do you often run the dishwasher and laundry at the same time? Do you have guests over often? These habits add to your hot water needs and should be part of the sizing calculation.Fixture Count and Appliance Requirements
The number of fixtures and appliances that use hot water impacts the size of your heater. Faucets, showers, dishwashers, and washing machines all add to the total demand. Each fixture has a flow rate, usually measured in gallons per minute (GPM). Adding up the GPM for all fixtures you plan to use at once gives you a clear idea of your peak water flow needs. For example:| Fixture Type | Typical Flow Rate (GPM) |
|---|---|
| Shower | 2.5 |
| Kitchen Faucet | 1.5 |
| Dishwasher | 1.0 |
| Washing Machine | 2.0 |
Calculating the Right Tankless Water Heater Size
To find the right tankless water heater size, you need to figure out how much hot water you use at once and how warm you want the water to be. This means knowing the flow rate in gallons per minute and the temperature rise needed. Using charts can help you match these numbers to the correct unit size. Practical examples show how these calculations work for different family sizes.Understanding Gallons Per Minute (GPM)
Gallons per minute (GPM) is the amount of hot water you use at the same time. You add up the flow rates of all the fixtures you might use together. For example:- Shower: about 2.5 GPM
- Kitchen faucet: about 1.5 GPM
- Bathroom sink: about 1.0 GPM
Using Sizing Charts Effectively
Sizing charts help match your GPM and temperature rise to the right heater size. Temperature rise means how much the heater must raise the water temperature from cold to hot. For example, if your incoming water is 50°F and you want 120°F, the rise is 70°F. A chart might look like this:| GPM | 50°F Rise | 70°F Rise | 90°F Rise |
|---|---|---|---|
| 3 | Small | Medium | Large |
| 5 | Medium | Large | X-Large |
| 7 | Large | X-Large | XX-Large |
Example Calculations for Common Households
If you have a family of four, you might use around 6 to 7 GPM during peak times. For example, two showers (2.5 GPM each) plus a kitchen faucet (1.5 GPM) total 6.5 GPM. If you live where the incoming water is 55°F and you want it heated to 120°F, your temperature rise is 65°F. Checking your sizing chart, you’d need a large or medium-large unit depending on the exact specs. For a single person or couple, the flow rate might only be 2–3 GPM. At the same temperature rise, a small or medium unit would work fine. If you’re unsure or want help, Splash Plumbing in Anaheim can guide you through sizing and install the right unit so your hot water needs are met every time.Selecting Between Gas and Electric Models
Choosing between gas and electric tankless water heaters means thinking about how each performs, what it takes to install them in your home, and how much energy they use. These factors will help you pick the best fit for your hot water needs and budget.Performance Differences
Gas models usually deliver hot water faster and in greater amounts than electric ones. They heat water by burning natural gas or propane, which gives them a stronger flow rate. This makes gas heaters a good choice if your household uses a lot of hot water at once. Electric tankless units heat water using electric elements. They might not produce as much hot water at once but work well for smaller homes or when the demand is lower. Both types provide hot water on demand, but gas models often succeed where you need higher volume and flow.Installation Considerations
Gas water heaters require a gas line and proper ventilation for safety. Installing them may mean extra work if your home doesn’t already have a gas hookup. This can add to the installation cost and time. Electric models are easier and usually cheaper to install, especially if you already have a sufficient electrical supply. They don’t need vents and take up less space, which can be helpful in smaller homes or tight areas. Splash Plumbing can guide you through the installation process, making it smooth whether you choose gas or electric.Energy Efficiency Comparisons
Both models save energy compared to traditional tank heaters because they only heat water when you need it. Gas heaters often use less energy per gallon than electric ones when sized right. Electric units are typically more efficient in converting energy to heat since they don’t lose heat through a flue or vent. However, if your electricity comes from a non-renewable source, your environmental impact might be higher compared to natural gas. To decide what’s best, consider your local energy costs and availability.Installation and Space Requirements
When installing a tankless water heater, knowing the exact space and system upgrades needed is key. You will need room for proper ventilation and clearance, plus possible updates to your electrical or gas lines to ensure the unit runs safely and efficiently.Ventilation and Clearance Needs
Tankless water heaters must have enough space around them to allow air to flow freely. This helps the heater work well and prevents overheating. Usually, you need to leave at least a few inches of clearance on all sides. The typical size of these heaters is about 20 x 27 x 10 inches, but check the specific model you pick. Proper ventilation is essential. If your heater uses gas, it needs a vent to remove harmful fumes. You may need to install a new vent or make sure the existing one meets building codes. Placing the heater in a spot where air can move naturally, like in a utility room or garage, often works best.Upgrading Electrical or Gas Lines
Your tankless water heater will likely require more power or gas flow than older units. Electric models usually need a dedicated circuit with the right amperage to avoid overloads. The wiring should meet local electrical codes, so you might need an electrician. Gas models must have piping that can supply enough gas for the heater to reach its full capacity. If your current gas line is too small, it may cause poor performance or safety issues. Upgrading to a larger line is common, as is ensuring proper pressure. If you’re unsure whether your home’s systems meet these requirements, Splash Plumbing in Anaheim can inspect and make sure everything is ready for your new heater.Common Sizing Mistakes to Avoid
Choosing the wrong size tankless water heater can lead to problems with hot water supply and increased costs. Knowing the risks of sizing too small or too large helps you pick the right model that fits your home’s needs.Undersizing Risks
If your tankless water heater is too small, it won’t keep up when multiple taps or appliances need hot water. This means your showers could end with cold water or your dishwasher may not clean properly. Undersized units may run constantly at full capacity, causing faster wear and higher energy use. It’s important to calculate the peak flow rate — how many gallons per minute (GPM) of hot water your household uses at once — and match the heater’s capacity to that number. Living in cooler climates also means your heater must work harder to raise water temperature. Undersizing can lead to frustration and extra repair costs over time.Oversizing and Cost Implications
A tankless heater that’s too large may seem like extra insurance, but it wastes money. Larger units cost more upfront and can use more energy than needed for your typical hot water demand. Oversized heaters may cycle on and off too often, which reduces their efficiency and lifespan. This can cause uneven heating and higher utility bills without much benefit. Balancing cost and performance means finding a size that meets your home’s flow rate and temperature needs without going too big.When to Consult a Professional
Choosing the right size tankless water heater might seem simple, but it can get tricky. If you’re unsure about calculating flow rates or temperature rises, it’s a good idea to call a professional. These numbers matter because the wrong size heater won’t give you enough hot water or could waste energy. A plumber can help you figure out your household’s peak hot water needs. They consider how many people live with you, the number of bathrooms, and appliances using hot water. This can be especially helpful if you have unusual water usage or special heating needs. If your home has complex plumbing or multiple water outlets running at once, trusting a pro can save you time and money. Professionals also know local codes and can recommend the best units for your area. Here are signs you should get expert help:- You don’t know the gallons per minute (GPM) needed
- You’re replacing an old unit and unsure about new sizing
- Your home has extra demands like radiant heating or multiple bathrooms
- You want to avoid costly mistakes
Final Tips for Choosing the Right Size
When picking a tankless water heater, remember two main things: your home’s maximum flow rate and the temperature rise needed. This means you need to think about how many taps or showers you might use at once and how cold the water is before heating. If you live somewhere cold, like parts of Orange County in winter, your unit needs more power to heat the water. If your incoming water is warmer, such as in summer or warmer climates, you can choose a smaller unit. Here are some quick tips to help:- List out how many hot water fixtures you use at the same time.
- Check your area’s water temperature to know the temperature rise needed.
- Avoid buying too big; it can cost more and waste energy.
- Don’t go too small either, or your water won’t stay hot during heavy use.
Frequently Asked Questions
Choosing the right size tankless water heater depends on knowing how much hot water your home needs at once and the temperature change required. You also need to think about how many bathrooms you have, the type of fuel your heater uses, and whether replacing an old system affects sizing.What factors should I consider when sizing a tankless water heater for my home?
You need to consider your home’s maximum flow rate and the temperature rise needed. The flow rate is how many gallons per minute (GPM) of hot water you use when multiple fixtures run at the same time. Temperature rise is the difference between incoming water temperature and desired hot water temperature.How do I calculate the flow rate needed for my household’s tankless water heater?
Add the flow rates of all fixtures likely to run at once. For example, a shower might use 2.5 GPM, and a sink might use 1.5 GPM. Add those numbers together to get your total flow rate. Use this number when choosing your heater size.What are the implications of choosing a tankless water heater that’s too small?
A unit that is too small won’t keep up with your hot water needs. You may run out of hot water during busy times. It can also make your system work harder, which lowers efficiency and might wear it out faster.Is there a guideline for matching tankless water heater size with the number of bathrooms in my home?
Yes. For a home with 2-3 bathrooms, a heater with a flow rate around 7-9 GPM usually works well. Larger homes might need units with higher flow rates to supply hot water to all bathrooms and fixtures running at once.How do electric and gas tankless water heaters differ in sizing requirements?
Gas units usually provide higher flow rates and can handle larger temperature rises. Electric models may need to be sized smaller or used for point-of-use applications unless you have enough electrical capacity. Your fuel type affects sizing choices.Can I replace my traditional tank water heater with a tankless one of the same size?
Not always. Tankless heaters work differently. Instead of tank capacity, size is based on flow rate and temperature rise. You might need a larger or smaller unit depending on your household’s hot water use and climate. Splash Plumbing can help you pick the right fit.Meet the Author
