Can An Inverter Be Too Big?

Inverters’ sizes are defined by their Operating Wattage rating. It is essential to note the Surge Wattage rating of the inverter is when deciding on what size inverter to invest in. An accurate list of all the electrical appliances and devices you wish to power from the inverter.

Inverters have to be sized for sufficient operational wattage and cope with surge loads for short periods. More often, the size of an inverter is too small to cope with additional loads. Inverters can become too big, and it is good to install a separate inverter and dedicate specific loads.

Installing the right sized inverter or inverters in parallel requires the user to do an accurate survey of current and future power loads:

  1. Record all current electrical appliances and devices in the household or workshop
  2. Record whether the device requires AC or DC and what the operational Watt-rating is of each device
  3. Also, take note of the surge wattage of appliances that require inductive loads during startup
  4. Record what future electrical devices you plan to install, e.g., EV car charger, heat-pump, swimming pool pump, and their Watt requirements

Let’s look at how you can use the results of your electrical device survey to correctly design your power supply system and define the right size inverters, solar panels, charge controllers, battery bank, and other components.

The Design And Sizing Of Your Power Supply System

Whether you are designing a small uninterrupted power supply (UPS) inverter battery system to power your laptop, cell phone charger, TV, and data router in the event of a power outage, or you are designing a comprehensive system to manage all your power requirements and harvest renewable energy in a grid-tied system, you need to size all components of the system correctly.

The place to start is to determine how much power you need to generate, store and convert to a format required by your electrical appliances and devices.

Inverter Application Chart
Application Device / EquipmentOperating WattageSurge Wattage
Air Compressor 3.25 HP27008100
Air Compressor 1 HP20006000
Air Compressor 0.75 HP15004500
Water Heater45005500
Clother Dryer18005000
Well Pump22505600
Impact Drill 1/2″15004500
Bench Grinder 8″15004200
Space Heater15001500
Hammer Drill13504050
High Pressure Washer10003600
Sump Motor8001600
Pump Motor8001300
Shop Vacuum750900
Fax Machine7001500
Laser Printer7501500
Microwave Oven600600
Desktop Computer500500
Battery Recharger200200
Cell Phone5050

Complete a thorough survey of your current and future potential power needs and decide how much redundancy you want to build into the system. Redundancy is required as the sun does not always shine to produce solar energy, and the wind does not always blow to generate wind energy.

Having your power supply tied to the supply grid allows you to sell your solar and wind-generated power to the grid when these sources are producing optimal amounts of energy. This is called a grid-tied system.

Another redundancy measure is to have a large battery bank installed. You can charge from the grid during off-peak times (when power is cheap) and discharge via inverters to power your household appliances during peak demand times (when power is most expensive).

A dedicated battery bank can also be installed in an off-grid system to supply the necessary power. The system you design should not be vulnerable to the failure of single components like an inverter but rather have separate inverter channels that each power a dedicated number of appliances.

Let’s assume that you have determined that your maximum planned power usage would be equivalent to 8kWh per year. The average American household has an energy usage of about 10,715 kWh of electricity per year. We will thus design a system to generate 10kW of solar power.

Why Is Bigger Better When Designing Solar Power Systems?

Big wattage solar systems to power homes have several benefits and require the same effort to design and install. Big inverters cost less per Watt generated than small inverters. A good quality 10kW inverter will cost an equivalent of $0.27 per Watt as opposed to $0.57 per Watt for a 3kW inverter.

Big solar arrays and big inverters work better with off-grid battery systems. The cost of Lithium-Iron-Phosphate (LFP) batteries is rapidly coming down as the supply of these batteries grows.

A large solar array can be designed to optimally charge the battery bank even during winter and cloudy weather. A more extensive solar system will improve the return on investment of your battery bank.

An extensive solar system also can add the fast charger required for electric cars giving you another source of payback on your solar investment. Make yourself independent of the energy price shocks that accompany every global crisis.

Electric cars are the future of mobility. You can fill up your EV with power generated from your solar system, which makes you independent of utility power suppliers.

If you plan to charge your EV with grid power, you have to get ready for a significant power bill. Why not instead invest the money you are going to spend with others to make yourself energy independent.

Big solar installations at your home will help you to contribute to decarbonizing the economy meaningfully. You become a producer and not a consumer of power. You are no longer exposed to the whims and mercies of the fickle oil and gas energy markets.

The cost of your solar power system will be amortized within as little as five to eight years and will last for at least twenty-five to thirty years. If you have the space available to install big solar, don’t waste any more time. Your return on investment is assured.

More than a significant financial decision, you will be living in harmony with our planet and become fully aware of how we can lighten our burden on the earth’s resources.


See also: What Is A Solar Inverter? (Explained With Examples)

Photo of author
Elliot has 20+ years of experience in renewable technology, from conservation to efficient living. His passion is to help others achieve independent off-grid living.

SolVoltaics is an affiliate and an Amazon Associate, we earn from qualifying purchases - at no extra cost to you.