How Much Solar Power Does It Take To Run A Heater?

How much solar power does it take to run a heater?

Many homeowners are interested in using solar power to run appliances and heat their homes, but determining how much solar power is needed to run a heater can be challenging given all the variables involved. Knowing the solar power requirements for heating is useful for homeowners considering installing solar panels to understand system sizing and costs. The amount of solar power needed depends on several key factors like the heater’s wattage rating, the home’s climate and insulation, and the number of daylight hours available for solar energy generation. This article provides an overview of solar power requirements for home heating, including details on system sizing calculations, real-world case studies, and cost considerations. Understanding solar power needs for heaters can help homeowners evaluate if solar energy is a viable option to lower utility bills and utilize renewable energy.

Heater Power Consumption

The power consumption of heaters depends on the type of heater and its size. Some key points on typical heater wattages:

– Electric space heaters for home use are usually rated between 750-1500 watts at max power. A common rating is 1500 watts (1.5 kW) according to sources.

– Smaller electric space heaters may be in the 750-1000 watt range. Larger ones designed to heat bigger rooms or whole floors can be 3000+ watts.

– Gas heaters are often between 30,000-50,000 BTUs. This equals around 8,800-14,650 watts.

– Radiant heaters like quartz or ceramic infrared models tend to be in the 1000-1500 watt range.

– Central heating and furnace systems can use 20,000-100,000+ BTUs for residential systems, depending on the home size.

So in summary, electric portable space heaters tend to consume 1000-1500 watts. Gas and central heat systems have higher wattage equivalents due to heating larger areas.

Sizing a Solar System

To determine the solar panel system size needed for a given electrical load like a heater, you first need to calculate the power consumption of the load. According to the U.S. Department of Energy, a typical portable electric space heater requires around 1500 watts (source).

Next, you need to estimate the number of peak sun hours for your location, which is the equivalent number of hours per day when solar irradiance averages 1,000 watts per square meter. The National Renewable Energy Laboratory provides maps of average daily solar radiation by region (source). For example, the central U.S. averages 4-6 peak sun hours per day.

To determine the solar array size in watts, take the load wattage (1500 watts for a portable heater), multiply it by the number of peak sun hours (say 5 hours), and add 10-20% more capacity to account for system inefficiencies and days with less sunlight. So for this example, the calculation would be: 1500 watts x 5 hours x 1.2 = 9,000 watts or a 9 kW solar array.

When shopping for solar panels, the wattage rating refers to the panel’s output under standard test conditions. So for a 9 kW array you would need around 30 x 300W panels. PV Watts tools provided by NREL can help fine tune your solar system size calculations (source).

Solar Irradiation

Solar irradiation, also known as insolation, refers to the amount of solar energy received on a given surface area over a period of time. It is measured in kilowatt-hours per square meter per day (kWh/m2/day). Solar irradiation varies significantly based on geographic location and local climate conditions.

Areas that receive abundant sunshine and limited cloud cover will have higher solar irradiation levels. For example, desert regions like the Southwestern United States average 6-8 kWh/m2/day solar irradiation, considered excellent for solar power generation. In contrast, the Pacific Northwest which sees more rainfall and overcast days only receives 3-4 kWh/m2/day, making it a less ideal solar location. The National Renewable Energy Laboratory provides solar irradiation data maps that compare the solar potential across different U.S. regions.

Higher latitudes also receive less solar irradiation than equatorial regions. Singapore, located near the equator, averages about 4.5 kWh/m2/day irradiation, while Berlin, Germany at a higher latitude receives just 2.9 kWh/m2/day. The Global Solar Atlas allows you to compare the solar irradiation globally based on geographic coordinates.

When sizing a solar system, it is critical to understand the solar irradiation levels for your specific location. Areas with abundant solar resources will require fewer solar panels to produce the same energy output. Consulting solar irradiation maps can give installers an accurate starting point for system design.

Other Factors

In addition to solar irradiation, the efficiency of a solar PV system can fluctuate throughout the year due to several other factors. According to Dynamics LR (, these include:

  • Weather and climate conditions like cloud cover and temperature
  • Orientation and tilt angle of solar panels
  • Type and quality of solar panels installed
  • Inverter and wiring losses
  • Shading from nearby objects like trees or buildings
  • Soiling from dust, dirt, snow, etc. accumulating on panels

Trace Software ( notes that the efficiency of solar panels decreases as temperature increases. In very hot conditions, efficiency losses can reduce energy production by 10-25%.

The time of year also impacts solar production. Days are shorter in winter, meaning less sunlight hours. The sun’s angle is also lower in the sky during winter. These seasonal differences mean solar panels may produce 50% or more energy in summer versus winter (Eco Green Energy,

Accounting for these various factors is important when sizing a solar system to adequately power a heater throughout the year. Extra panel capacity is often added to compensate for real-world efficiency losses.

Battery Storage

Batteries play a critical role in solar systems for heaters by storing excess solar energy captured during the day for use at night or during cloudy weather. This storage capacity reduces the size and number of solar panels needed since the system does not have to produce all the energy needed in real time (1). Without batteries, solar systems for heaters would need to be significantly oversized to provide enough power when the sun is not shining.

The more storage capacity available, the less solar generation is needed. For example, a solar system with 3 days of battery storage would need a smaller solar array than one with only 1 day of storage. With ample storage, the solar system can build up excess energy on sunny days to provide heating at night or through extended cloudy periods. Most experts recommend at least 2-3 days of storage capacity for solar systems running heaters to ensure reliable operation (2).

However, batteries increase system costs and require special maintenance. There are also efficiency losses during the charging and discharging process. So battery capacity should be properly sized based on the solar resource availability and load requirements to balance performance and economics (1). Overall, integrating the right amount of battery storage enables solar systems to effectively power heaters using the intermittent energy from the sun.



Case Studies

A case study on an off-grid solar system in Somersby, NSW showed how an 8.16kW system was designed for a newly constructed home (Case Study: Off Grid Solar System Somersby NSW 2250 8.16kW). The system consisted of 32 x 255W panels and 24 x 90Ah deep cycle batteries. This provided enough solar power to meet the energy needs of the home’s two occupants. After a year, the system was performing well with excess solar energy being used to power a pool pump.

Another case study examined an off-grid solar system installed at a bus shelter in Indonesia (Design Methodology of Off-Grid PV Solar Powered System). This 3.6kW system used 12 x 300W panels and 12 x 200Ah batteries. It successfully powered lighting, fans, mobile chargers and a TV at the bus shelter. Performance monitoring over 6 months showed the system met the location’s energy demands.

A student project looked at an off-grid solar system powering a tiny home in California (Living Off the Grid with Renewable Energy: A Case Study). This 2kW system with 8 x 250W panels and 4 x 100Ah lithium-ion batteries reliably met the energy needs for lighting, a refrigerator and electronics in the 200 sq. ft. home.

Cost Analysis

The cost of a solar heating system can vary greatly depending on the size and components needed. According to Modernize, a basic solar water heating system for a home costs $3,000 to $5,000 on average. However, a complete solar thermal system with storage for space heating and hot water can cost $25,000 or more.

For a simple electric space heater, the average power consumption is around 1,500 watts. So to run a 1,500 watt heater for 8 hours would require 12,000 watt-hours (1,500 x 8) per day. A 6 kW solar panel system could produce around 18,000 watt-hours per day in good sunlight conditions. This means a 6 kW solar system may be adequately sized to run a 1,500 watt space heater during daylight hours without needing battery storage (Source).

In terms of payback time versus fossil fuels, solar thermal systems can recoup their costs within 8 to 12 years typically. The payback period depends on system costs, energy costs in your area, and available tax credits and incentives. With rising energy prices, solar heating continues to make better financial sense for homes and businesses (Source).


While solar energy has many advantages, there are some limitations to consider when using it for home heating:

Intermittency: Solar energy production depends on the amount of sunlight available, which varies by season, weather, and time of day. Cloudy days and nighttime reduce or halt energy generation. This can make it challenging to rely solely on solar for all heating needs.

Storage needs: Solar energy must be stored in batteries for use when the sun isn’t shining. Heating systems require a large storage capacity, which adds significant cost. Batteries must also be replaced periodically.1

Space requirements: Collecting enough solar energy for home heating requires a large number of solar panels. This may not be feasible for homes with limited roof or land space.2

Upfront cost: While solar provides free ongoing energy, the high initial installation and equipment costs can deter adoption. Rebates and incentives can offset some expenses.

Efficiency losses: Solar energy capture and battery storage both lead to some energy losses. This means more panels and batteries may be needed.

Weather impacts: Solar panels produce less energy in cloudy or cold weather when heating needs are high. Production can drop significantly with snow covering panels.

Overall, while solar can provide clean renewable energy for heating, relying completely on it may be prohibitive. It often works best paired with another energy source for consistent heating during periods of low sunlight.


In summary, the key factors that determine the solar power needed to run a heater include the size and power draw of the heater, the amount of sunlight available based on location and weather, the efficiency of the solar panels, and the size of the battery storage if needed. Smaller, more efficient heaters will require less solar power, while larger heat pumps may require more extensive solar setups. Solar irradiation levels also play a major role, with sunnier locations able to generate more electricity from the same solar system.

Advancements in solar panel technology are leading to higher efficiency levels, allowing homes to meet more of their energy needs with smaller solar installations. Battery storage can help provide overnight power but also increases system requirements. Overall, with proper planning and system sizing, solar energy can be a viable option for powering electric and hydronic heating systems in many climates.

The future outlook for solar-powered heating is positive, as solar technology continues to improve and costs come down. Market projections show strong growth in the solar thermal sector in both residential and commercial applications. With the electrification of heating to replace gas furnaces, and new construction designed to be highly energy efficient, the use of solar power for heat pumps and other electric heating is expected to expand considerably in the coming decades.

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