Do solar panels actually help you save money? I crunched the numbers on my own panels during the hottest week of the year so far

Solar panels are easily the best home upgrade I've ever paid for, and over the past six years, I've saved thousands of dollars on my energy bill because of them. Naturally, the amount of benefit I get from my 12-panel system depends on a bunch of factors, the most important of which is the weather. The more sun there is, the more energy you can generate, which means a better return on investment.

I live in the U.K., which just endured a pretty big heatwave, which meant this week was the hottest week of the year so far. That coincided with some of the clearest skies I've seen for several months, and it sent my solar panels into production overdrive. Hotter temperatures mean my energy usage skyrocketed, and that had me wondering just how effective my panels were at keeping my energy bills down.

So I decided to do the math to figure out what was going on — and calculate just how much money my solar panels saved me over a seven-day heatwave (May 22 to May 28).

Latest Videos From

For the sake of my own convenience, I'll be doing all my math in Pounds Sterling (£) and pence (p), and will convert the totals to dollars at the end.

The solar situation at my home

I don't have a particularly large house, but the roof space is almost completely uninterrupted — meaning I had room for quite a few solar panels. My system is made up of twelve 345 watt solar panels, with a maximum production capacity of 4.14 kilowatts. While I could theoretically generate 4.14kW from this setup at any given moment, I've never actually seen my panels generate more than 3.5kW at a time — and that's a rarity.

Eight of my panels are at the front of the house, facing the south when most of the energy is generated, while the other four are in the back room facing north. I also have a 3.3 kWh home battery, but it doesn't really factor into these calculations since all the energy it stores either gets used up or exported at some point throughout the day.

My current electric plan means that I pay 22.17p for every kWh of electricity I import from the grid, plus a 41.35p daily standing charge — which is kind of like a rental fee for maintaining a connection to the national power grid. That standing charge doesn't change, and means my weekly electricity bill will always be at least £2.90 ($3.86) even if I don't use any electricity. My provider also pays me 12p for every kWh of electricity I export to the grid, which ensures I get some money back for any excess solar power that I don't personally use or store.

It's also worth mentioning that I don't have any HVAC installed that would drive up my electricity usage. My heating and hot water is powered by a gas boiler, rather than a heat pump, and any air conditioning I get to enjoy comes from a vented portable unit rather than a central air system.

My energy usage over the past week

Let's get down to the math of it all, starting with my own electricity usage over the course of the week-long heatwave.

As you can see in the table below, you can see a breakdown of my electricity usage for each day — based on the stats in Levelise — the app I use to monitor and manage my solar system. You can see my total energy usage, how much my panels generated, as well as how much energy flowed between my house and the grid.

As you can see the generated energy exceeded my total usage every single day, and by a considerable amount. I consumed 83.02 kWh of energy throughout the week, while generating 145.01 kWh — 59.88 kWh of which was exported back to the grid in exchange for cold hard cash.

Sadly, this wasn't enough for me to be completely off grid. Part of this is because my energy use is stretched out over a 24-hour period, while solar generation is limited to 12 or 13 hours of the day. The other factor to consider is that there's a limit to how much power my panels can generate at any given time. If my usage exceeds that number, power from the grid flows in to keep everything switched on.

Sadly, the relative cost of grid energy versus exports (22.17p vs 12p) means that any imported power makes a dent in my overall savings. However, I was still able to save a considerable amount compared to not having solar panels at all.

The actual monetary savings

Knowing about energy usage and generation in kilowatt hours is one thing, but it's harder to visualize in terms of actual monetary value. So I crunched the numbers and figured out exactly what all this energy was costing me, as seen in the table below.

If I had no solar panels installed and was importing all my energy from the grid, this entire week would have cost me roughly £18.41 ($24.73), plus an additional £2.90 for the standing charge, making my total for the week £21.30 ($28.61). As much as I would like to marvel at the nice round number, it's still a lot of money to spend on electricity — and I pin most of the blame on my portable air conditioner.

But thankfully, I did have solar panels, which made a huge dent in the amount of grid energy I needed to import. Thanks to those 12-sheets of metal and glass, I only had to pay roughly £4.10 ($5.51) for all the additional electricity I needed — or £7 ($9.40) when you add the standing charge on top.

If you just look at the total cost of electricity itself, this means my panels saved me roughly £14.31 ($19.22) over the course of this seven-day heatwave. Then you have to take export earnings into account, with my 59.88 kWh of exported energy earning me an additional £8.63 ($11.63) of credit that is applied to my energy account.

This means that my energy provider actually owes me around £1.63 ($2.20) after everything is taken into consideration.

That's a pretty weak amount of profit, especially when you consider the fact that I also have to pay my gas bill. But it doesn't change the fact that I would have had to pay considerably more money if I didn't have a rooftop solar system subsidizing my electricity usage.

Bottom line

I will admit that a heatwave is not a particularly normal occurrence where I live, even in summer. Normally, the weather throughout the summer months is peppered by periods of cloud and rain, both of which have a noticeable impact on solar generation. It is true that the summer months are generally rather fruitful from a power generation perspective, which means the pricier winter energy bills don't seem quite so extreme.

When it comes to solar generation on your own home, the amount you can save is going to be totally dependent on your circumstances. More expensive electricity means fewer savings, but having a large roof means you can get more panels installed and boost your generation capacity. Likewise, panels installed in states like Arizona or Nevada, which get more sunlight on average, are going to reap the benefits more than they would in Alaska or Vermont.

But in the end, it doesn't matter whether you're a tried-and-tested tree-hugger or a diehard proponent of fossil fuels; there are real monetary benefits to being able to generate your own electricity at home. The number may not be huge in isolation, but they do add up over the course of months and years — which could help offset the cost of running your home.

Follow Tom's Guide on Google News and add us as a preferred source to get our up-to-date news, analysis, and reviews in your feeds. Subscribe to Tom's Guide on YouTube and follow us on TikTok.

More from Tom's Guide

• Expert reveals the one solar panel mistake costing you money — and how to fix it
• I tested this portable solar generator and it managed to bring power to places my home solar system couldn't reach
• 9 ways to get more out of your solar panels this winter