There are three main ways to go solar:

  • Off-grid: A true “off grid” dwelling is not physically connected to the electric utility, and generally uses batteries to provide baseload power, recharged by solar panels and/or a fossil fuel generator. Being off-grid means you have significant limitations to how many power loads you can use (as battery technology is still relatively expensive and there are hard limits to how much power you can produce in winter!) and only makes sense in situations that are extremely difficult to connect to the utility grid, i.e. you build a home up on a mountain or on an island.
  • Grid-tied: 99% of solar installations in the United States are grid-tied, meaning they still have a physical connection to the public utility grid, but can also produce their own solar power. Under this arrangement, you treat the utility like a gigantic battery – anytime the sun is out, your home produces and consumes its own solar electricity, but any excess you can send out to the grid. At night or during crummy weather, you use power from the electric grid like normal. Utilities are required by law to give you credits for any solar power you send out to the grid, under an arrangement called ‘net metering.’ It varies, but in most places, you get a 1:1 credit, or 1 unit of exported solar = 1 unit of utility credit you can use later.
  • Grid-tied with battery backup: The best of both worlds, is have a grid-tied solar array (which allows your solar to produce as much power as it possibly can with no limits to battery size) with battery backup (so that if the grid goes down you have a source of backup power). Modern battery backup solutions include Tesla Powerwall, sonnen, and Maine-made Pika Energy systems.

Sizing Up

For this guide, we’re going to assume you’re going with one of the grid-tied solar options.

In a grid-tied solar electric system, with or without battery backup, the goal is generally to achieve net-zero, meaning, at the end of the year your home will have produced as much electricity as it has consumed. This is not always possible (especially if you’re heating with solar and also running an electric car) but it’s a worthy goal!

“Plug Load” Electricity Estimate

Before we get into heating and cooling, we start with getting an estimate for ‘plug loads’ — the amount of power you need for your household appliances, electronics, well pump, etc.

This is tricky! No two families are alike, and two families living in the same home can have VERY different electricity bills depending on occupant behavior. Once you start to work with a ReVision Solar Design Specialist, we’ll do a more thorough analysis, and ideally get a professional energy designer in the mix to build a more complex model.

For now, here’s a cheatsheet to give you a rough idea how much power you’re likely to use in your new home, and how much solar you’ll need to produce to meet your needs.

What’s in a Watt?

kilowatt-hours explainedSome terminology…

Electricity is measured in units called kilowatts (1,000 watts). This represents instantaneous power – much like miles per hour measure the speed of a vehicle, but not its travel over time.

Electricity is billed in units called kilowatt-hours. This is the amount of total energy as an expression of kilowatts and time. This is like measuring how many miles a car traveled, and averaging the miles-per-hour over that time period.

Solar panel arrays are usually sold in kilowatts (the ‘nameplate’ rating of the panels in full sun) but its far more important to understand how much energy they will produce over time – or their kilowatt-hour (kWh) potential.

Each 1kw of solar panels (roughly 3) = 1,200 kWh a year of solar production on a decent solar site in our region.

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