UIL (UIL) 8-K Results of Operations and Financial Condition

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1Q ’10 Earnings

- transforming investment into future value

1Q 2010 Earnings Conference Call

May 4, 2010

EXHIBIT 99.1

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1Q ’10 Earnings

Certain statements contained herein, regarding matters that are not historical facts, are forward-looking
statements (as defined in the Private Securities Litigation Reform Act of 1995). These include statements
regarding management’s intentions, plans, beliefs, expectations or forecasts for the future. Such forward-
looking statements are based on the Corporation’s expectations and involve risks and uncertainties;
consequently, actual results may differ materially from those expressed or implied in the statements.
Such risks and uncertainties include, but are not limited to, general economic conditions, legislative and
regulatory changes, changes in demand for electricity and other products and services, unanticipated
weather conditions, changes in accounting principles, policies or guidelines, and other economic,
competitive, governmental, and technological factors affecting the operations, timing, markets, products,
services and prices of the Corporation’s subsidiaries. The foregoing and other factors are discussed and
should be reviewed in the Corporation’s most recent Annual Report on Form 10-K and other subsequent
periodic filings with the Securities and Exchange Commission. Forward-looking statements included
herein speak only as of the date hereof and the Corporation undertakes no obligation to revise or update
such statements to reflect events or circumstances after the date hereof or to reflect the occurrence of
unanticipated events or circumstances.

Important Note to Investors

James Torgerson

President and Chief Executive Officer

Richard Nicholas

Executive Vice President and Chief Financial Officer

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1Q ’10 Earnings

1Q ’10 consolidated earnings of $16.1 million, or $0.53 per share,
compared to $12.0 million, or $0.48 per share, in 1Q ’09

ØNet income grew 34%, an increase of $0.05 per share compared to the 1Q ‘09; in
spite of $0.10 per share earnings dilution from May ‘09 equity offering

ØStrong first quarter performance

»$19M distribution rate increase effective 1/1/10 + $21.6M ’09 & ‘10 pension recovery

»Continued focus on managing operating costs

»Decoupling provides Commission-determined level of revenue

»Transmission net income growth - higher rate base and equity capitalization

1Q 2010 Financial Results - Summary

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1Q ’10 Earnings

* Competitive Transition Assessment

Quarter Ended March 31,

2010

2009

Difference

UI

Distribution, CTA* and Other

9.9

$

6.8

$

3.1

$

Transmission

6.7

6.1

0.6

Total UI Net Income

16.6

$

12.9

$

3.7

$

UIL Corporate

(0.5)

(0.9)

0.4

Total Net Income

16.1

$

12.0

$

4.1

$

Average Shares Outstanding - Basic

30.0

25.2

4.8

EPS

0.53

$

0.48

$

0.05

$

The dilutive effect of the May 2009 issuance of 4,600,000 shares of common

stock in the first quarter of 2010 was $0.10 per share.

1Q 2010 Financial Results

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1Q ’10 Earnings

ØDecoupling adjustment net of acceleration
of previously approved ‘10 rate increase

ØIncreases in UI’s distribution rates

ØDecrease in customer service allocation
percentage to transmission

ØUncollectible write-offs are stabilizing and
less uncollectibles are being allocated to
other business units

ØIncreased depreciation and amortization
due to amortization of ’09 pension
regulatoryasset

Transmission - growth in net income

ØEarning on higher rate base and equity capitalization

Quarter Ended

March 31, 2010

Favorable/(Unfavorable)

(In Millions)

Operating revenues

Regulatory true-up items incl. decoupling adjustment

(2.1)

$

Distribution rates & pricing

6.0

Sales volume

0.8

Operation and maintenance (O&M) expense

Customer service - allocated

(0.2)

Uncollectibles

(0.5)

Depreciation and amortization

(1.6)

Other income and (deductions)

1.6

Interest expense

(0.5)

Other, net

1Q ‘10 Earnings Details Compared to the Same Period in ‘09

Distribution, CTA & Other

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1Q ’10 Earnings

Solid Liquidity Position Enabling Future Growth

ØNo plans to issue additional equity in 2010

ØUnrestricted cash and temporary investments of $11.4M as of 3/31/10

Ø$162M available under $175M short-term credit facility as of 3/31/10

ØDPUC approved financing plan for up to $275M incremental debt during
2010 through 2013

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1Q ’10 Earnings

Liquidity outlook

ØUIL & UI have a $175M joint credit facility due
12/22/11 ($50M of limit available for UIL)

»Short-term borrowings outstanding under this
facility were $13M as of 3/31/10

ØUIL also has an uncommitted money market
loan facility

»No outstanding balance as of 3/31/10

ØUI must pay off $121.5M equity bridge loan to
fund its portion of the contribution to GenConn
on the commercial operation date for each
facility, Devon 6/’10, Middletown 6/’11

»Borrowings under this facility as of 3/31/10 were
$114.4M

ØUIL had $49.3M of long-term debt at the
holding company as of 3/31/10, maturing in
February 2011

Debt maturity schedule as of 3/31/10($M)

NONE

Solid liquidity position enabling future CapEx plans

$27.5M refunded 2/1/10

$4.3M sinking fund payment 2/16/10

$31.8

Debt Maturity and Liquidity Details

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1Q ’10 Earnings

	Approximate 2010 Net Income *	2010 EPS
The United Illuminating Company
Distribution, CTA & Other	$31 - $33	$1.02 - $1.09
Transmission	26 - 28	0.85 -0.93
GenConn	2 - 3	0.07 - 0.09
Total UI	$59 - $63	$1.98 - $2.10
Corporate	(3) - (2)	(0.09) - (0.05)
Total UIL	$57 - $62	$1.92 - $2.07
2009 Actual	$54.3	$1.94
Previous Guidance	$56 - $61	$1.87 - $2.02

Expectations are not intended to be additive

* Rounded to the nearest million

Guidance Assumptions

Ø2010 EPS estimates include $0.15 per share dilution from May 2009 equity issuance, when compared to 2009

ØEarnings from CTA are expected to decline $0.06-$0.08 per share in 2010

ØGenConn Devon is expected to be on-line in June 2010

ØSustainable O&M cost savings in the Distribution business

ØDistribution & CTA has a reasonable opportunity to earn its allowed ROE of 8.75% in 2010

ØTransmission is expected to earn a weighted average return on equity of 12.3% to 12.5%

Increased 2010 EPS Guidance as of May 4, 2010

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1Q ’10 Earnings

2010 Outlook

Connecticut’s economy

ØUnemployment remains below national average

»Non-seasonally adjusted rate as of 4/16/10:9.3% CT // 10.2% national

ØCT job losses are now easing

»State added 6,400 jobs in 1Q ‘10

Our outlook

ØExpect slight to modest economic growth in our service territory in 2010

ØCT economy is stabilizing

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1Q ’10 Earnings

2010 Regulatory Update

ØDistribution rate increase effective 1/1/10

»Incremental $19.4M over 2009 plus additional $21.6M for ’09 & ’10 pension cash recovery

»$2.4M to the bottom line in equity return

ØDecoupling analysis for the 2009 rate year ending 2/3/10 was filed with the
department on 4/1/10(DN 08-07-04)

»Identified a net regulatory liability of approximately $0.5M - to be applied against the 2010
rate year decoupling adjustment

4Proposal seeks to net various regulatory adjustments against the 2009 rate year decoupling
regulatory asset of $1.5M

»Requested that the department decide if decoupling mechanism will remain in place
beyond the 2010 rate year

»On 4/28/10 the DPUC reopened the 2008 distribution rate case to examine the 2009
decoupling adjustment proposal and pilot (DN 08-07-04RE02)

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1Q ’10 Earnings

2010 Regulatory Update - cont.

ØGeneric ROE proceeding (DN 09-10-06)

»Comments from interested parties filed

»Interrogatories issued on 4/22/10

»Hearings set for end of June

»Final decision expected mid October

ØNew DPUC commissioner - Anna Ficeto - effective 2/24/10

»Former Chief Legal Counsel for the Governor of CT

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1Q ’10 Earnings

UI Equity Bridge Loan

Ø$121.5M in total à $114.4M drawn as of
3/31/10

»$57M due 6/1/10 with Devon in-service

»$64.5M due 6/1/11 with Middletown in-service

NRG Equity Bridge Loan

Ø$121.5M in total

GenConn Project Financing

Ø$291M in total à includes $48M working
capital facility

Financing

Ø50/50 debt/equity

Status

ØDevon Plant

ØMiddletown Plant

»Construction underway

ØGenConn rate case for establishment of ‘10
revenue requirements filed in 12/09

»Additional information on UIL’s website in the Investors
section on the Regulatory page

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1Q ’10 Earnings

Middletown

In-service June 2011

Devon

In-service June 2010

Construction site photos as of the March timeframe.

GenConn Energy - Current View of Progress

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1Q ’10 Earnings

Changes from Previous Estimate

ØDistribution

»Core Support spending moved out
to future years

4UI’s central facility peak construction
shift from ’10 to ’11

ØTransmission

»Capacity spending moved out to
future years

4Union and Grand Avenue substations
spending shift from ’10 to ’11 and ‘12

Full 10-year Capex Plan Refresh .... coming Mid 2010

Current ’10 Estimate of $272M

Previous ’10 Estimate of $295M

** Changes in Capex primarily do
not affect rate base until 2012 **

2010 Capital Expenditure Forecast Update

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1Q ’10 Earnings

Progressive pure-play
electric utility

Transmission focus

(FERC Regulated)

Regulation

ØVirtually 100% regulated

ØLong history of National 1st quartile reliability performance

Ø20 year leader in Conservation & Load Management programs

ØSmart Grid - ahead of the curve

Ø2010 composite return on equity of approximately 12.3%-12.5% and capital structure of 50% equity

ØIdentified future investment opportunities

ØProven ability to execute, e.g. Middletown-to-Norwalk transmission line

ØRecent distribution rate case includes favorable items such as revenue decoupling mechanism,

pension tracker and cost of debt tracking mechanism

ØExpected enhanced stability and predictability of earnings

UIL: progressive pure-play electric utility with significant growth opportunities and an attractive dividend yield

Conservative financial
strategy

ØCommitment to investment grade credit profile

ØDisciplined capital investment program

ØConsistent history of dividend payments

High probability
growth

Ø$1.7 billion 10-year capital expenditure program

ØBase plan provides significant growth - 90+% probability of occurrence

ØGenConn: cost-of-service electric generation development underway

Investment Highlights

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1Q ’10 Earnings

Q&A