Can Solar Panels Heat a House?

Can solar panels heat a house? In this article, we’re going to check how much electric power solar panels produce and how you can use this power to heat your home. We’re going to consider the effects of different seasons of the year on your solar power generation and the power yields of different roof sizes!

Quick answer: Yes, solar panels can heat a house. To heat your home on solar panels only, you will need to install 19 solar panels to power electric heating, or 7 solar panels to power a heat pump with a coefficient of performance (CoP) of 3.

How much power do solar panels produce?

Average solar panels produce between 250 – 400 Watts of power. The higher the Wattage a solar panel can produce, the more premium it is and the more expensive it is. Usually, solar panels are priced in dollars per watt.

Higher wattage is always preferable.

Of course, the wattage rating of solar panels is measured under ideal conditions in laboratories. In reality, the wattage heavily depends on the weather, the orientation of the roof, time of day, and sun intensity.

An average solar panel in the US produces about 1.8kWh a day. That is the amount of energy to run a 1800W device for one hour. At an average electricity rate of 14 cents per kWh, one solar panel reduces your electricity cost by 28 cents.

How many solar panels can a roof fit?

The US-average roof size is 1,700 square feet (about 160m²). An average solar panel is 17,6 square feet. Theoretically, an average roof could fit 101 solar panels.

If you know your roof’s area, just divide it by the average solar panel size to get the theoretical maximum amount of solar panels you can install.

Of course, there are practical limitations to this. Due to the geometry specific to your roof, you can only cover parts of your roof. And usually, you cover only the one side of your roof that yields the most electric power.

The realistic maximum amount of solar panels a home can fit is between 30 and 40. However, even that is more than you need!

Most homes install 20 to 24 solar panels rated 340W, which is enough to cover 100% of their energy usage.

Can I heat my house using solar panels?

To heat your home using solar panels, your solar panels have to absorb enough power from the sun. Let’s check how much energy, solar panels produce in the winter.

How much power do solar panels produce in the winter?

However, usually, you want to heat in the wintertime, where there are fewer sun hours and the sun rays have a lower inclination compared to summer.

However, there is an interesting, counterintuitive effect: In the cold, solar panels gain efficiency. The cold air reduces internal electric resistances.

According to an experiment by “The Solar Nerd” located in Buffalo:

On an average winter day, one solar panel produces around 0.25kWh of energy. On a sunny winter day, average solar panels can produce up to 1kWh of energy. And on a day where your roof is covered in snow, the power production is close to zero.

This looks like pretty bad values. However, this is where net metering gets beneficial. If you feed in your energy into your city’s electric grid, the excess energy you produce in summer makes up for the lack of energy in winter.

“If you have net metering, it means that the excess electricity you generate in the summer will be banked as credits that you can “spend” in the winter.”

thesolarnerd.com

So, it does not really matter whether your solar panels produce less in winter and more in summer, which is initially a concern for most people. Just make sure that net metering is supported in your area.

How much power do you need to heat a house?

An average home needs about 12,000kWh of heat energy a year (source). A heat pump with a coefficient of performance (CoP) would need 4,000kWh of energy a year, while other regular heating systems would require the full 12,000kWh.

So, you already see that the heating system you use matters. 

Also, the way you heat matters. Do you heat the full house? Or do you need to heat just one room in a blackout emergency situation?

To heat one medium-sized room to a comfortable temperature in winter, you will need around 750W of power. That’s the equivalent heat output of a regular space heater on moderate settings. In 24h that’s 750W x 24h = 18kWh a day. To heat during the cold half of the year, you would need 6 months x 30 days x 18kWh = 3,240kWh.

With a heat pump with a CoP of 3 that would be only about 1,080kWh.

To heat a whole house, you need 12,000kWh of energy per year or 4,000kWh with a heat pump. To heat a single room, you need 3,240kWh of energy per year or 1,080kWh with a heat pump.

How many solar panels do you need for heating?

Here’s how many solar panels you need to cover just the heating of your home considering an average production rate of 1.8kWh per solar panel per day.

The formula used in the table is (yearly energy / 1.8kWh * 365). Feel free to plug your own yearly heating energy consumption into the formula to calculate your personal required amount of solar panels. You should be able to find your annual energy consumption on your heating bill.

Finding:

Yes, you can heat a house on solar panels. You need 19 solar panels to heat a house using electric heating, or 7 solar panels to heat a house using a heat pump.

To heat a single room, you need 5 solar panels using electric heating and 2 when using a heat pump.

However, keep in mind that these numbers are just to cover heating. To run your entire house’s electric grid on solar panels, you will need to install at least 20 more solar panels.

So, to make an entire home fully energy independent including the heating, you need 39 solar panels with classic electric heating or 27 solar panels when you have a heat pump.

Now that we know how many solar panels you need to heat a house, let’s have a look at how you can do it.

How can you convert solar panel power to heat?

If you feed your solar panel power back into your neighborhood’s electric grid and you make use of net metering, you don’t have to worry about setting up complex heating systems.

The net metering ensures that you can heat independently of your solar panel’s current power output.

To heat your house using solar panel power, you can only use electric heating methods. Two different methods pop out.

Electric space heaters

The simplest way to heat your home using the electricity of your solar panels is electric resistance heating.

This could be either a central heating unit in your home that is already electricity-based, or you can buy simple space heaters to keep your home warm.

To mimic the look and feel of classic radiators, I recommend electric oil-filled radiators.

If you want to be very efficient, you can use infrared space heaters. These radiate infrared heat waves directionally. You can always point them towards you. Instead of heating the entire room, you heat just yourself.

Generally, in a family home, I recommend using oil-filled radiators, because they are able to produce a comfortable warmth.

There are other types of space heaters such as ceramic space heaters, but for heating entire homes, I recommend either infrared or oil-filled.

Electric space heaters are rated at 1,500W. One space heater alone will consume 13,140kWh of energy a year, which is more than the 12,000kWh an average home needs for heating.

The formula is 1.5kW x 24h a day  x 365 days a year =  13,140kWh

(yes, I know, you probably won’t run your space heater 24/7 for the whole year, but you get the point. And you can tweak the numbers!)

This means that an average 1500W electric space heater produces a lot more heat than you need. To realistically heat a house, I recommend getting 3 electric space heaters and running them on moderate settings. Place each space heater in a different room to cover your entire home.

This reduces the wattage of each space heater and improves safety while still providing the same amount of heat.

Check this article to see my recommended oil-filled radiator: The Best Oil-Filled Radiator

Air source and ground source heat pumps

With heat pumps, you can use your solar panel’s power to heat your house. Heat pumps work just like the reverse of a fridge or an air conditioner. They extract heat energy from the air outside or the ground and pump it into the house.

Heat pumps work even if it’s colder outside than inside! And they move more heat energy than the amount of electric energy you put into it.

This makes heat pumps one of the very few appliances with efficiencies bigger than 100%.

The downside of heat pumps is that their cost of installation is $4000-$8000, which is very high and pays for itself only after many years.

If you just got solar panels, the expense might be too high.

But remember that installing a heat pump also increases the worth of your home. So, the money is not really lost.

Energy storage without net metering

Heating your house on solar panels is reliably possible due to net metering. The surplus of energy produced in the summer makes up for the lack of energy produced in the winter.

Net metering acts as a virtual storage of your electric energy. You feed energy into the electric grid and you can withdraw it anytime.

If your area does not support net metering, for example when you are in a remote place or you are living in a mobile home not connected to an electric grid, heating in the wintertime using solar panels only is barely possible.

Without net metering, with an average solar panel’s daily energy production of 0.25kWh during winter, you need either a lot of solar panels to produce sufficient energy, or a supplementary heat source, such as a wood stove.

Another option is to install energy storage batteries to store surplus energy from the summer. However, they are very expensive, inefficient, and have too little capacity for heating.

Does it make sense to heat a house using solar energy?

Whether it makes sense to heat your home using solar panels depends on your situation. Solar panels are expensive to install and they deteriorate over time.

If you don’t have net metering heating with solar panels is never realistically feasible.

If your area has net metering, yes, heating your house using solar energy can be worth it. Especially with a heat pump.

The alternatives oil, gas, or wood can be, however, more reliable, easier to access, and require almost no maintenance.

The answer is very difficult. I’d say the following:

• Heat pump and net metering: Solar panel heating is worth it.
• Electric heating and net metering: Solar panel heating is worth it, but there’s potential for improvement. You need to install a dozen more solar panels when compared to using heat pumps. Make sure your home is well-insulated to improve heating efficiency.
• No net metering: With an average home and average amount of solar panels, you can not realistically cover the energy consumption for heating during wintertime. Especially in unstable, cold, and cloudy weather where you need the most heating, solar panels generate the least energy.
  Stick to other energy sources such as wood, oil, or gas. This article will help you: The 21 Cheapest Methods to Heat a Room & House

Conclusion

Yes, solar panels can heat a house. But you can not realistically heat independently of your neighborhood’s electric grid.

Electric and heat pump heating off solar panel energy is only possible with net metering where your area’s electric provider guarantees the storage of your surplus energy generated in the summer.

If you want to generate heat independently, you need to stick to classic energy sources such as wood, oil, or gas.