Smart thermostats, shopping vouchers, boiler cover, LED lightbulbs and more are available free with the right energy tariffs. But should you be tempted by the offers, or would you be better off switching your gas and electricity elsewhere and buying the freebie yourself?
We've looked at deals from the biggest energy companies and crunched the numbers to reveal how good the offers really are. We've also discovered how much money you can save if you don't get taken in by the marketing claims.
We've found dual-fuel deals which will cut your energy bills compared with the same company's cheapest tariff (if you're a medium energy user), and one where you could be around £86 worse off.
You can also find out which deal is actually £219 more expensive than switching to the cheapest tariff on the market and buying the freebie yourself.
Read on to see our verdict on freebies and energy deals from British Gas, Co-operative Energy, EDF Energy, Eon, Scottish Power, SSE and Utility Warehouse.
We've delved into whether the freebies you're offered to persuade you to switch to a particular tariff are really worth it. Don't be tempted by the marketing ads until you've read the results of our research.
Watch our video, below, then keep reading for more information about each company and its offer.
Already know which company you're interested in? Then use our links to go straight to it, or scroll to read each one:
EDF Energy and Eon are both selling gas and electricity tariffs that chuck in freesmart home products, such as smart thermostats and smart light bulbs.
EDF Energy's deal could save you more than £30 per year compared with its own cheapest deal. Eon's works out as around £86 more expensive.
But with both tariffs, you'd save most by switching to the cheapest tariff on the market (£815 per year for Outfox the Market Whack! January Tariff Medium) and buying the smart home products separately. If you're tempted by a smart thermostat, check our .
British Gas also offered a tariff with free Hive smart home products, but this is now discontinued.
How much does it cost?£1,124 per year for a medium user, including the Netatmo thermostat (which EDF states costs £199 including installation) and an Amazon Echo (2nd generation) (£89.99).
Should I switch?It works out slightly cheaper to buy the Connect + Control tariff if you want the Netatmo thermostat, Amazon Echo and are keen to be an EDF Energy customer.
Buy them separately (you can get the Netatmo thermostat for £149 plus £50 installation, and the £89.99 Amazon Echo) with EDF's cheapest tariff and you'd be £33 worse off per year.
But pick the cheapest deal on the market, buy the Amazon Echo and Netatmo separately (and install the smart thermostat yourself, saving £50), and you could save £189 per year.
What else do I need to know? Your boiler will need to be compatible with the thermostat and have heating controls with a programmer. The exit fees are substantial: £135 per fuel if you leave before the end of the two-year deal.
Which? survey verdict: was placed joint 22nd out of 31 companies, as voted by customers in our annual energy company survey. Though it's joint-highest-ranked of the Big Six firms, alongside Eon, smaller firms are much better loved by customers.
EDF's customers gave it four stars for its bills and phone customer service, but were less positive about other aspects.
How much does it cost? £1,193 per year for a medium user, including a Tado smart thermostat which Eon states costs £249 (including £50 installation).
Should I switch? If you're set on being an Eon customer, you'll save more (around £86 per year for a medium user) by picking its cheapest tariff (costing £908 per year for the average user) and buying the Tado smart thermostat separately.
It costs £109 direct from Tado, plus £90 installation. Most customers install it themselves though, Tado says, so you could save more.
Save an extra £148 per year by picking the cheapest tariff on the market, buying the Tado thermostat direct from Tado and installing it yourself.That's a total of saving of £324.
What else do I need to know? This tariff is only available for 500 customers, and you must pay by direct debit and claim your Tado thermostat within 14 days of receiving email confirmation. It's a two-year tariff, with exit fees of £75 per fuel if you want to leave early.
Which? survey verdict: finished in joint-22nd position with EDF Energy, out of 31 companies in our most recent energy satisfaction survey. It scored a consistent three stars across the board, according to customers: good but not great.
This tariff came with a Hive Welcome Home Plan and Hive Live 'at no additional cost'. This meant you got two Hive Active light bulbs, a Hive motion sensor and Hive Active Plug. You also got the Hive Hub and access to Hive Live (which gives you discount on other Hive products, warranty and text alerts).
How much did it cost? £1,076 per year for a medium user, including the Hive Welcome Home Plan worth £155 (according to British Gas).
Should I switch? If you want to be British Gas customer, this was the most cost-effective way of getting the Hive Welcome Home Plan. Now you'll need to buy it separately (it costs £9.99 per month) with British Gas' current cheapest tariff, which costs £39 more per year than the HomeEnergy Fix tariff did.
But you'll save even more by switching to the cheapest dual-fuel deal on the market (Outfox the Market's Whack! Tariff, £815 per year) and buying the Hive Welcome Home Plan separately.
Co-operative Energy, Npower and SSE are offering vouchers worth up to £100 with their tariffs. Though tempting, you can save more than the value of the vouchers by choosing a cheaper deal.
How much does it cost? SSE offers two two-year fixed deals which come with £50 to spend (for dual-fuel): choose between Love2Shop and Currys/PC World. They cost £1,109 per year for a dual-fuel customer who uses a medium amount of gas and electricity.
Should I switch? Though £50 to spend with a retailer is tempting, this isn't good value for money for a medium user, even compared with SSE's cheapest deal. Choose that (1 Year Fixed v14), spend £50 at the retailer over two years and you'll be £31 up per year.
Pick instead the cheapest deal on the market with another energy firm and you'll pay £269 less per year than SSE's Fix and Shop deal. Take off the equivalent of the £50 voucher, and that's you saving £219 plus having fifty quid to spend on whatever you want.
What else do I need to know? These two-year fixed tariffs come with £25 exit fees per fuel if you want to leave early.
Which? survey verdict: finished joint 24th out of 31 companies in our annual energy survey. Customers ranked most aspects of its service as average, so it has plenty to improve on, though they were more positive about its phone customer service.
How much does it cost? £1,009 per year for two years. You get a £50 travel voucher per fuel (so £100 if you buy gas and electricity).
Should I switch? The cheapest Co-op tariff available around England, Scotland and Wales costs just £11 less than this one per year, so you're better off choosing this deal, if you want to stick with the Co-op and will use the travel vouchers.
But the cheapest deal on the market will save you £194 compared with Co-op's Fix and Fly - leaving you an extra £94 to spend on your travels.
What else do I need to know? The travel vouchers come with limitations. There's a minimum spend of £500 per voucher, and you can use one voucher per booking. They're not valid on currency and must be used before the end of 2018.
Plus there's an exit fee of £30 per fuel if you switch before the two-year tariff is up.
Which? survey verdict: ranked above the Big Six in our energy companies satisfaction survey. This is an improvement on recent years but it still has a way to go. Customers did rate its bills, phone customer service, and value for money reasonably positively though.
Npower is offering a free Take Time Out membership on all of its tariffs at present. Worth £60 for a year (it costs the same to buy it direct from Take Time Out), it gives you discounts on restaurants, hotels, gyms and other entertainment.
But with Npower's cheapest tariff costing £1,011 per year, you can save far more than the value of the membership by switching to the cheapest deal on the market. That'll cost you a total of around £875 per year (including buying your own Take Time Out membership), saving you £136 per year.
Among the other bigger energy companies, Scottish Power and Utility Warehouse are also offering freebies. Read on to find out whether Scottish Power's boiler care deal, or Utility Warehouse's free light bulb offer are worth your money.
Should I switch? It works out about the same cost per year to buy Scottish Power's Boiler Care Plus tariff, or pick its cheapest tariff and pay for Boiler Care separately. There's a £7.60 difference per year.
Pick the cheapest tariff on the market however, and pay for Scottish Power's Boiler Care separately, and you'll save £167 per year.
Which? survey verdict: ranks jointly with British Gas, in 26th position out of 31 companies in our 2018 energy companies satisfaction survey. Customers only gave it two stars for its complaints handling.
Utility Warehouse is offering to replace all the light bulbs in your home with LEDs if you're a customer on its Gold Energy or Double Gold tariffs.
How much does it cost? The cheapest of these is Double Gold fixed, costing £998 per year for gas and electricity for a medium user. Utility Warehouse states that replacing all your light bulbs typically costs £300-£500, including fitting.
Should I switch? This is the most cost-effective way of getting the lightbulbs offer from Utility Warehouse.
Install 39 of them (the same number on which Utility Warehouse based its calculations) and fit them yourself (avoiding Utility Warehouse's £100 fitting charge) and it will cost you £27 less per year than Utility Warehouse's Double Gold fixed tariff.
What else do I need to know? Utility Warehouse says it will give you a lifetime guarantee for the bulbs it fits so you'll not need to replace another light bulb, as long as you stay on its eligible tariff.
Pricing data is from Energylinx and based on a dual-fuel medium user (using Ofgem averages of 3,100kWh electricity and 12,000kWh gas per year), paying by direct debit with paperless bills. Data is averaged across regions and correct on 28 Jan 2018.
We looked at tariffs from energy firms with a 1% market share or more, according to energy regulator Ofgem's data. First Utility, Ovo Energy and Utilita were not offering tariffs with freebies at the time of our research. Where tariffs are two years long, we've split the cost of the freebie equally over two years.
We subtracted the cost of the freebie, according to the company, from the total cost of the tariff, and compared the price with the company's cheapest deal. We also compared this with the price of the freebie, bought elsewhere (where possible), and the cheapest deal on the market.
If you are a low energy user, freebies will be worth more relative to the overall cost of the tariff. So they could be better value if you don't use much energy. But if you're a high-energy user, a freebie will be a smaller percentage saving on the overall tariff - you'll probably be able to save even more by choosing the cheapest tariff on the market.