1500 Watt Heater: What Size Inverter & Solar Panel Needed?

This is going to be a short but thorough guide on running a 1500-watt heater on solar power. 

To run a heater on solar power you’d need an inverter (which will convert the DC current into AC current)

Battery bank to store the power, & solar panels to charge the battery.

If you're a newbie I would recommend you to watch this video before going further to get a better understanding of electricity basics (amps, volts, watts...)

What size inverter for 1500 watt heater?

To run a 1500-watt heater you need at least 2000 watt pure sine wave inverter

The inverter will convert the DC (Direct current) coming from the batteries into AC (alternating current). Because the heater requires AC power to run.

Watch this video to understand the difference between modified vs Pure sine wave inverter. 

In short, you’d need a pure sine wave type inverter to run a space heater.

Here’s a chart on what size of cable you need with any size inverter. 

What size of cable should I use with my inverter and battery?
Cable size guide for inverter

Use the above chart as an example to pair the right size wiring for your inverter

12 Vs 24 Vs 48 volt inverter?

The input voltage of your inverter should match the battery voltage.

For Example, if you have a 12v solar system you’d need an inverter that can accept 12v input.

Now before calculating what size solar panel and battery you need for the solar power heater, first let's have a look at how much electricity a 1500-watt heater consumes

1500 watt Heater Power Consumption

A 1500-watt heater will consume 1500 watts of power when running. But most oil-based heaters do not stay on all the time depending on the room temperature.

So a 1500-watt inverter will consume about 1kW (1000 watts) per hour if it's running continuously for a few hours.

It's like some heaters work like AC, when the room temperature reaches a certain level the AC will decrease the power consumption 

This exactly will happen in the case of the heater. But make sure it’ll happen when you’re at least running your heater for about 2-3 hours. 

But this value is based on the assumption. The total power consumption will depend on various factors.

So, I’ll take 1500 watts of power consumption per hour as an example to make the calculations more accurate. 

1500 watt Heater Power Consumption - Chart

Running HoursPower Consumption
1 hour1.5 kWh
2 hours3 kWh 
3 hours4.5 kWh
5 hours6 kWh
6 hours7.5 kWh
24 hours36 kWh
1500 watt heater power consumption chart

What Size Battery For 1500 watt Heater?

Battery capacity is measured in amp-hours, but the wattage consumption of the heater is measured in watts

To convert watt-hours into amp-hours, use this formula.  

Amp-hours = Watt / volts

Watt will be the total power consumption of your heater. For example, the running hours of your heater are about 3 hours per day ( 1500 * 6 = 4500 watt-hours or 4.5kWh )

Volts will determine the voltage of your solar battery, whether you’d go for a 12v or 24-volt system. 

Now let's make the calculation

4500/12v = 375 amp-hours

4500/24v = 187 amp-hours

DC To AC Conversion Loss

As i have discussed earlier we require an inverter that will converter the DC into AC to run a heater and the inverters are not 100% efficient

Most of the inverters are about 90% efficient. This means there will be a 10% power loss when converting DC into AC

Now let's add an extra 10% to the value which we have just calculated

375Ah * 1.1 or + 10% = 412 amp-hours (@ 12v system)

187Ah * 1.1 or + 10% = 205 amp-hours (@ 24v system)

You’d need 400 amp-hours with 12 volts or 200 amp-hours with 24 volts to run a 1500-watt inverter for 3 hours daily. 

Battery Types & DoD limit

Every battery type has a different depth of discharge limit, which means you can only discharge them at a certain percentage

Lead-acid, AGM, and Gel batteries have a DoD limit of 50%. However, lithium-ion (LiFePO4) can be fully discharged up to 100%. 

For a lead-acid type multiply the required amp-hours by 2. 

Relates Post: Amps To Watts Calculator: How Many Watts In A 12-volt Battery?

Required Battery Size To Run a 1500-watt Heater - Table

1500 watt inverter running hoursRequired Lithium Battery Size @ 12vRequired Lithium Battery Size @ 24v
Table: what size battery for 1500 watt heater


  • To run a 1500-watt heater for 1 hour you’d need a 12v 125Ah lead-acid or 24v 60Ah Lithium  battery 
  • To run a 1500-watt heater for 5 hours you’d need a 12v 3x 200Ah lead-acid or 24v 3x 100Ah Lithium batteries 

How many solar panels To Run 1500 watt heater?

To run a 1500 watt for an hour you’d need a 1650Wh of DC power (an extra 10% to cover the DC to AC conversion loss

On average a solar panel produces about 80% of its rated power output in one peak sun hour. 

This percentage is based on my 200-watt solar panel’s 30 days of output data.

  • 1 peak sun hour = 1kW/m2 of sunlight intensity 

To calculate how many peak sun hours your location receives use this PV solar calculator

1 - Enter your complete for more accurate information or just enter your city name.

How to calculate peak sun hours

2 - Click on the result tab

How to calculate peak sun hours
How many peak sun hours in florida?

Now you'll be able to see the number of total peak sun hours your location receives.


My location receives on average 5.8 hours of peak sunlight (annually). So to run a 1500-watt heater for 3 hours daily, what size solar panel i would need? 

1500 * 1.1 = 1650 or 1.65 Kwh (to cover the DC to AC conversion losses) 

1650 * 3 (running hours) = 4950 watt-hours

4950 / 5 (peak sun hours) = 990 watt-hours 

990 * 1.2 (to cover the solar panel’s inefficiency) = 1188 watt-hour

You’d need a 1.2kWh solar panel system to run a 1500-watt heater for 3 hours (considering 5 peak sun hours per day).

Make the calculation according to your location and need. 

Related FAQ's

Can I run a heater off solar panels?

Yes, you can run a heater off solar panels but it would require a large solar system to run your heater with solar panels for many hours which will cost you more.

What size inverter to run a 1500-watt heater?

2000w 12V inverter will be enough to run a 1500w heater.

What size battery to run a 1500-watt heater for an hour?

12v 140Ah lithium battery can run a 1500w heater which will draw 100% of power from the battery but if you're using AGM or gel batteries a 12V 300Ah AGM or gel battery will run the heater for one hour.

How much does it cost to run a 1500-watt heater?

The electricity cost in the USA on average is $0.1319 per kWh so a 1500w heater will cost $0.20 per hour and $4.80 in 24 hours

I hope this guide was helpful to you, if you have any queries Contact Us. Thank You! 

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Chris Tsitouris is a renewable energy professional with 10+ years of experience as Director of Engineering at Solar Spectrum, previously working as Project Manager at SunPower and Energy Analyst at the National Renewable Energy Laboratory. As a thought leader, Chris has authored numerous articles and research papers.

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